Artigo descreve a descoberta do exoplaneta HATS-6b, um exoplaneta parecido com Saturno, porém pesado como Júpiter ao redor de uma estrela anã-M, o tipo de estrela mais abundante na nossa galáxia.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
Large turbulent reservoirs of cold molecular gas around high-redshift starbur...Sérgio Sacani
This document discusses observations of six lensed starburst galaxies at redshift ~2.5 using the Atacama Large Millimeter/submillimeter Array (ALMA). The key findings are:
1) ALMA detected emission and absorption lines of the CH+ molecule in the spectra of five out of the six galaxies, indicating dense shocks and highly turbulent reservoirs of cool gas extending over 10 kiloparsecs outside the starburst regions.
2) The broad CH+ emission lines trace shocks moving at ~40 km/s within dense gas, while the absorption lines reveal turbulent reservoirs with velocities of ~400 km/s.
3) The turbulent reservoirs have radii of 10-20 kilopar
A nearby yoiung_m_dwarf_with_wide_possibly_planetary_m_ass_companionSérgio Sacani
This document summarizes the identification of two young objects, TYC 9486-927-1 and 2MASS J21265040−8140293, as a likely very wide binary system. It presents revised astrometry showing they have common proper motion. Spectroscopy of the secondary yields a radial velocity consistent with the primary. Analysis of lithium absorption and kinematics suggests an age range of 10-45 Myr, with the secondary having an estimated mass in the planetary mass regime. If confirmed, this would be the widest known exoplanet system at over 4500 AU separation.
A higher efficiency_of_converting_gas_to_stars_push_galaxies_at_z_1_6_well_ab...Sérgio Sacani
Galáxias formando estrelas em taxas extremas a nove bilhões de anos atrás eram mais eficientes do que a média das galáxias atuais, descobriram os pesquisadores.
A maioria das estrelas acredita-se localizam-se na sequência principal onde quanto maior a massa da galáxia, mais eficiente ela é na formação de novas estrelas. Contudo, de vez em quando uma galáxia apresentará uma explosão de novas estrelas que brilham mais do que o resto. Uma colisão entre duas grandes galáxias é normalmente a causa dessas fases de explosões de formação de estrelas, onde o gás frio que reside nas grandes nuvens moleculares torna-se o combustível para sustentar essas altas taxas de formação de estrelas.
A questão que os astrônomos têm feito é se essas explosões de estrelas no início o universo foram o resultado de se ter um suprimento de gás abundante, ou se as galáxias convertiam o gás de maneira mais eficiente.
Um novo estudo, publicado no Astrophysical Journal Letters de 15 de Outubro, liderado por John Silverman, do Kavli Institute for Physics and Mathematics of the Universe, estudou o conteúdo do gás monóxido de carbono (CO) em sete galáxias de explosão de estrelas muito distantes, quando o universo tinha apenas 4 bilhões de anos de vida. Isso foi possível devido a capacidade do Atacama Large Millimiter/Submillimiter Array (ALMA), localizado no platô no topo da montanha no Chile, que trabalha para detectar as ondas eletromagnéticas no comprimento de onda milimétrico (importante para se estudar o gás molecular) e um nível de sensibilidade que só agora começa a ser explorado pelos astrônomos.
Os pesquisadores descobriram que a quantidade de gás CO emitido já tinha diminuído, mesmo apesar da galáxia continuar a formar estrelas em altas taxas. Essas observações são similares àquelas registradas para as galáxias de explosões de estrelas próximas da Terra atualmente, mas a quantidade da depleção de gás não foi tão rápida quanto se esperava. Isso levou os pesquisadores a concluírem que poderia haver um contínuo aumento na eficiência, dependendo em de quanto acima da taxa de se formar estrelas ela está da sequência principal.
A candidate super-Earth planet orbiting near the snow line of Barnard’s starSérgio Sacani
This document summarizes the discovery of a candidate super-Earth planet orbiting Barnard's star. Analysis of over 20 years of radial velocity measurements revealed a periodic signal of 233 days, attributed to a planet with a minimum mass of 3.2 Earth masses in a near-circular orbit near the star's snow line. Long-term monitoring also detected a possible second signal with a period over 6,000 days, which could be from a more distant planet or stellar magnetic activity cycle. Independent photometric and spectroscopic monitoring ruled out stellar activity as the cause of the 233-day signal. This candidate planet has one of the lowest minimum masses detected around an M dwarf star.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
Final Year Project - Observation and Characterisation of ExoplanetsLucy Stickland
This document summarizes a student report on the observation and characterization of exoplanets. It explores various exoplanet detection techniques, recent increases in Earth-sized planet discoveries, and relationships between stellar and planetary parameters. The student conducted photometry on three known transiting exoplanets - Hat-P-25b, Wasp-43b, and Wasp-2b - using the Sedgwick telescope. Light curves were produced and used to calculate planetary properties. A program called the Exoplanetary Pixelization Transit Model was created and tested to better fit light curves computationally.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
Large turbulent reservoirs of cold molecular gas around high-redshift starbur...Sérgio Sacani
This document discusses observations of six lensed starburst galaxies at redshift ~2.5 using the Atacama Large Millimeter/submillimeter Array (ALMA). The key findings are:
1) ALMA detected emission and absorption lines of the CH+ molecule in the spectra of five out of the six galaxies, indicating dense shocks and highly turbulent reservoirs of cool gas extending over 10 kiloparsecs outside the starburst regions.
2) The broad CH+ emission lines trace shocks moving at ~40 km/s within dense gas, while the absorption lines reveal turbulent reservoirs with velocities of ~400 km/s.
3) The turbulent reservoirs have radii of 10-20 kilopar
A nearby yoiung_m_dwarf_with_wide_possibly_planetary_m_ass_companionSérgio Sacani
This document summarizes the identification of two young objects, TYC 9486-927-1 and 2MASS J21265040−8140293, as a likely very wide binary system. It presents revised astrometry showing they have common proper motion. Spectroscopy of the secondary yields a radial velocity consistent with the primary. Analysis of lithium absorption and kinematics suggests an age range of 10-45 Myr, with the secondary having an estimated mass in the planetary mass regime. If confirmed, this would be the widest known exoplanet system at over 4500 AU separation.
A higher efficiency_of_converting_gas_to_stars_push_galaxies_at_z_1_6_well_ab...Sérgio Sacani
Galáxias formando estrelas em taxas extremas a nove bilhões de anos atrás eram mais eficientes do que a média das galáxias atuais, descobriram os pesquisadores.
A maioria das estrelas acredita-se localizam-se na sequência principal onde quanto maior a massa da galáxia, mais eficiente ela é na formação de novas estrelas. Contudo, de vez em quando uma galáxia apresentará uma explosão de novas estrelas que brilham mais do que o resto. Uma colisão entre duas grandes galáxias é normalmente a causa dessas fases de explosões de formação de estrelas, onde o gás frio que reside nas grandes nuvens moleculares torna-se o combustível para sustentar essas altas taxas de formação de estrelas.
A questão que os astrônomos têm feito é se essas explosões de estrelas no início o universo foram o resultado de se ter um suprimento de gás abundante, ou se as galáxias convertiam o gás de maneira mais eficiente.
Um novo estudo, publicado no Astrophysical Journal Letters de 15 de Outubro, liderado por John Silverman, do Kavli Institute for Physics and Mathematics of the Universe, estudou o conteúdo do gás monóxido de carbono (CO) em sete galáxias de explosão de estrelas muito distantes, quando o universo tinha apenas 4 bilhões de anos de vida. Isso foi possível devido a capacidade do Atacama Large Millimiter/Submillimiter Array (ALMA), localizado no platô no topo da montanha no Chile, que trabalha para detectar as ondas eletromagnéticas no comprimento de onda milimétrico (importante para se estudar o gás molecular) e um nível de sensibilidade que só agora começa a ser explorado pelos astrônomos.
Os pesquisadores descobriram que a quantidade de gás CO emitido já tinha diminuído, mesmo apesar da galáxia continuar a formar estrelas em altas taxas. Essas observações são similares àquelas registradas para as galáxias de explosões de estrelas próximas da Terra atualmente, mas a quantidade da depleção de gás não foi tão rápida quanto se esperava. Isso levou os pesquisadores a concluírem que poderia haver um contínuo aumento na eficiência, dependendo em de quanto acima da taxa de se formar estrelas ela está da sequência principal.
A candidate super-Earth planet orbiting near the snow line of Barnard’s starSérgio Sacani
This document summarizes the discovery of a candidate super-Earth planet orbiting Barnard's star. Analysis of over 20 years of radial velocity measurements revealed a periodic signal of 233 days, attributed to a planet with a minimum mass of 3.2 Earth masses in a near-circular orbit near the star's snow line. Long-term monitoring also detected a possible second signal with a period over 6,000 days, which could be from a more distant planet or stellar magnetic activity cycle. Independent photometric and spectroscopic monitoring ruled out stellar activity as the cause of the 233-day signal. This candidate planet has one of the lowest minimum masses detected around an M dwarf star.
This document summarizes a blind HI survey of the southern Milky Way zone of avoidance conducted with the Parkes radio telescope. The survey detected 883 galaxies at Galactic longitudes 212° < l < 36° and latitudes |b| < 5° to a sensitivity of 6 mJy per 27 km/s channel. Fifty-one percent of detections had known optical/near-infrared counterparts, while 27% had new counterparts identified. The survey delineated large-scale structures in the Puppis and Great Attractor regions for the first time. Several newly identified galaxy concentrations and clusters were revealed that help trace the Great Attractor Wall.
Final Year Project - Observation and Characterisation of ExoplanetsLucy Stickland
This document summarizes a student report on the observation and characterization of exoplanets. It explores various exoplanet detection techniques, recent increases in Earth-sized planet discoveries, and relationships between stellar and planetary parameters. The student conducted photometry on three known transiting exoplanets - Hat-P-25b, Wasp-43b, and Wasp-2b - using the Sedgwick telescope. Light curves were produced and used to calculate planetary properties. A program called the Exoplanetary Pixelization Transit Model was created and tested to better fit light curves computationally.
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
Evidence for a_distant_giant_planet_in_the_solar_systemSérgio Sacani
A descoberta de um novo planeta, atualmente não é uma manchete que chama tanto assim a atenção das pessoas. Muito disso, graças ao Telescópio Espacial Kepler, que já descobriu quase 2000 exoplanetas e todo instante uma nova descoberta é anunciada, certo? Mais ou menos, a descoberta anunciada hoje, dia 20 de Janeiro de 2016, é um pouco diferente, pois não se trata de um exoplaneta, e sim de um novo planeta no Sistema Solar, e esse é um fato que intriga os astrônomos a muitos e muitos anos.
Porém, temos que ir com calma com esses anúncios. No artigo aceito para publicação no The Astronomical Journal (artigo no final do post), os autores, Mike Brown e Konstantin Batygin, do Instituto de Tecnologia da Califórnia, apresentaram o que eles dizem ser evidências circunstâncias fortes para a existência de um grande planeta ainda não descoberto, talvez, com uma massa 10 vezes a massa da Terra, orbitando os confins do nosso Sistema Solar, muito além da órbita de Plutão. Os cientistas inferiram sua presença, por meio de anomalias encontradas nas órbitas de seis objetos do chamado Cinturão de Kuiper.
O objeto, que os pesquisadores estão chamando de Planeta Nove, não chega muito perto do Sol, no ponto mais próximo da sua órbita ele fica a 30.5 bilhões de quilômetros, ou seja, cinco vezes a distância entre o Sol e Plutão. Apesar do seu grande tamanho, ele é muito apagado, e por isso ninguém até o momento conseguiu observá-lo.
Não existe ainda uma confirmação observacional da descoberta, mas as evidências são tão fortes que fizeram com que outros especialistas como Chad Trujilo do Observatório Gemini no Havaí e David Nesvorny, do Southwest Research Institute em Boulder no Colorado, ficassem impressionados e bem convencidos de que deve mesmo haver um grande planeta nas fronteiras da nossa vizinhança cósmica.
Kepler-1647b is the largest and longest-period Kepler transiting circumbinary planet discovered to date. It orbits an eclipsing binary star system with an orbital period of approximately 1100 days, making it one of the longest-period transiting planets known. The planet is around 1.06 times the size of Jupiter and perturbes the times of the stellar eclipses, allowing its mass to be measured at 1.52 times that of Jupiter. Despite its long orbital period compared to Earth, the planet resides in the habitable zone of the binary star system throughout its orbit. The discovery of this unusual planetary system provides insights into theories of planet formation and dynamics in multiple star systems.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
This research article explores how the orbital configuration of Kepler-62f, a potentially habitable exoplanet in a five-planet system, could affect its climate and habitability. N-body simulations were used to determine the stable range of orbital eccentricities for Kepler-62f. Climate simulations using two global climate models then examined the planet's surface habitability across this range of eccentricities and for different atmospheric compositions. The simulations found multiple combinations of orbital and atmospheric parameters that could allow for surface liquid water on Kepler-62f, including higher orbital eccentricities coupled with high planetary obliquity or atmospheric CO2 levels above 3 bars.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
Know the star_know_the_planet_discovery_of_l_ate_type_companions_to_two_exopl...Sérgio Sacani
This document summarizes the discovery of additional late-type stellar companions to two exoplanet host stars, HD 2638 and 30 Ari B, using adaptive optics imaging. For both systems, the companions were found to share common proper motion with the primaries, indicating they are physically associated. The estimated orbital periods of the new companions are 130 years for HD 2638 and 80 years for 30 Ari B. This makes 30 Ari B the second confirmed quadruple star system known to host an exoplanet. The discoveries provide additional examples of how binary companions can influence exoplanet dynamics and formation.
Third epoch magellanic_clouud_proper_motionsSérgio Sacani
The document analyzes proper motion data from the Hubble Space Telescope to study the three-dimensional rotation field of the Large Magellanic Cloud (LMC) galaxy. It finds that:
1) The proper motion data implies a stellar dynamical center that coincides with the HI dynamical center from previous studies.
2) Combining the proper motion and line-of-sight velocity data provides insights into the LMC's rotation curve, disk viewing angles, and circular rotation speed of 91.7 km/s outside the central region.
3) The data paint a consistent picture of LMC rotation and yield improved constraints on the galaxy's distance, mass profile, and orbital history around the Milky Way.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
Water vapour absorption_in_the_clear_atmosphere_of_a_neptune_sized_exoplanetSérgio Sacani
This document summarizes research on the transmission spectrum of the exoplanet HAT-P-11b, a Neptune-sized planet. Observations from the Hubble Space Telescope and Spitzer Space Telescope detected water vapor absorption in the planet's atmosphere at a wavelength of 1.4 micrometers. Analysis of the spectrum indicates the atmosphere is predominantly clear down to 1 mbar and has a hydrogen abundance similar to solar values. Atmospheric modeling suggests a metallicity around 190 times that of the Sun's, in agreement with core accretion planet formation theories. This makes HAT-P-11b the smallest exoplanet to date with a detected molecular signature in its atmosphere, providing new insights into the composition and formation of Neptune-sized
1) The document analyzes data from the SuperWASP-South telescope to classify four stars - VSX013997, 017283, 026353, and 091251.
2) The author cleaned the raw data, used Period04 to identify pulsation frequencies for each star, and created phased light curves to classify the stars.
3) Based on the periods, amplitudes, and light curve shapes, the author classified three stars as RRab subtype RR Lyrae variables and one star as a rotating ellipsoidal variable.
The document summarizes findings from orbital magnetic field measurements taken by the MESSENGER spacecraft around Mercury. Key points:
1) Remanent magnetization has been detected in Mercury's crust, providing evidence that Mercury had a dynamo-generated magnetic field early in its history.
2) The magnetization is estimated to have an average age of 3.7-3.9 billion years, based on its presence across diverse terrain including the youngest volcanic deposits on Mercury.
3) Ancient field strengths that could have produced the observed magnetization range from Mercury's current dipole field strength to values similar to Earth's ancient field.
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
Evidence for a_distant_giant_planet_in_the_solar_systemSérgio Sacani
A descoberta de um novo planeta, atualmente não é uma manchete que chama tanto assim a atenção das pessoas. Muito disso, graças ao Telescópio Espacial Kepler, que já descobriu quase 2000 exoplanetas e todo instante uma nova descoberta é anunciada, certo? Mais ou menos, a descoberta anunciada hoje, dia 20 de Janeiro de 2016, é um pouco diferente, pois não se trata de um exoplaneta, e sim de um novo planeta no Sistema Solar, e esse é um fato que intriga os astrônomos a muitos e muitos anos.
Porém, temos que ir com calma com esses anúncios. No artigo aceito para publicação no The Astronomical Journal (artigo no final do post), os autores, Mike Brown e Konstantin Batygin, do Instituto de Tecnologia da Califórnia, apresentaram o que eles dizem ser evidências circunstâncias fortes para a existência de um grande planeta ainda não descoberto, talvez, com uma massa 10 vezes a massa da Terra, orbitando os confins do nosso Sistema Solar, muito além da órbita de Plutão. Os cientistas inferiram sua presença, por meio de anomalias encontradas nas órbitas de seis objetos do chamado Cinturão de Kuiper.
O objeto, que os pesquisadores estão chamando de Planeta Nove, não chega muito perto do Sol, no ponto mais próximo da sua órbita ele fica a 30.5 bilhões de quilômetros, ou seja, cinco vezes a distância entre o Sol e Plutão. Apesar do seu grande tamanho, ele é muito apagado, e por isso ninguém até o momento conseguiu observá-lo.
Não existe ainda uma confirmação observacional da descoberta, mas as evidências são tão fortes que fizeram com que outros especialistas como Chad Trujilo do Observatório Gemini no Havaí e David Nesvorny, do Southwest Research Institute em Boulder no Colorado, ficassem impressionados e bem convencidos de que deve mesmo haver um grande planeta nas fronteiras da nossa vizinhança cósmica.
Kepler-1647b is the largest and longest-period Kepler transiting circumbinary planet discovered to date. It orbits an eclipsing binary star system with an orbital period of approximately 1100 days, making it one of the longest-period transiting planets known. The planet is around 1.06 times the size of Jupiter and perturbes the times of the stellar eclipses, allowing its mass to be measured at 1.52 times that of Jupiter. Despite its long orbital period compared to Earth, the planet resides in the habitable zone of the binary star system throughout its orbit. The discovery of this unusual planetary system provides insights into theories of planet formation and dynamics in multiple star systems.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
This research article explores how the orbital configuration of Kepler-62f, a potentially habitable exoplanet in a five-planet system, could affect its climate and habitability. N-body simulations were used to determine the stable range of orbital eccentricities for Kepler-62f. Climate simulations using two global climate models then examined the planet's surface habitability across this range of eccentricities and for different atmospheric compositions. The simulations found multiple combinations of orbital and atmospheric parameters that could allow for surface liquid water on Kepler-62f, including higher orbital eccentricities coupled with high planetary obliquity or atmospheric CO2 levels above 3 bars.
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
Know the star_know_the_planet_discovery_of_l_ate_type_companions_to_two_exopl...Sérgio Sacani
This document summarizes the discovery of additional late-type stellar companions to two exoplanet host stars, HD 2638 and 30 Ari B, using adaptive optics imaging. For both systems, the companions were found to share common proper motion with the primaries, indicating they are physically associated. The estimated orbital periods of the new companions are 130 years for HD 2638 and 80 years for 30 Ari B. This makes 30 Ari B the second confirmed quadruple star system known to host an exoplanet. The discoveries provide additional examples of how binary companions can influence exoplanet dynamics and formation.
Third epoch magellanic_clouud_proper_motionsSérgio Sacani
The document analyzes proper motion data from the Hubble Space Telescope to study the three-dimensional rotation field of the Large Magellanic Cloud (LMC) galaxy. It finds that:
1) The proper motion data implies a stellar dynamical center that coincides with the HI dynamical center from previous studies.
2) Combining the proper motion and line-of-sight velocity data provides insights into the LMC's rotation curve, disk viewing angles, and circular rotation speed of 91.7 km/s outside the central region.
3) The data paint a consistent picture of LMC rotation and yield improved constraints on the galaxy's distance, mass profile, and orbital history around the Milky Way.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
The harps n-rocky_planet_search_hd219134b_transiting_rocky_planetSérgio Sacani
Usando o espectrógrafo HARPS-N acoplado ao Telescopio Nazionale Galileo no Observatório de Roque de Los Muchachos, nas Ilhas Canárias, os astrônomos descobriram três exoplanetas, classificados como Super-Terras e um gigante gasoso orbitando uma estrela próxima, chamada de HD 219134.
A HD 219134, também conhecida como HR 8832 é uma estrela do tipo anã-K de quinta magnitude, localizada a aproximadamente 21 anos-luz de distância da Terra, na constelação de Cassiopeia.
A estrela é levemente mais fria e menos massiva que o nosso sol. Ela é tão brilhante que pode ser observada a olho nu.
O sistema planetário HD 219134, abriga um planeta gigante gasoso externo e três planetas internos classificados como super-Terras, um dos quais transita em frente à estrela.
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
This document reports the discovery of a newly discovered optical Einstein ring (ER) called the "Canarias Einstein Ring". It was discovered serendipitously in imaging data from the Dark Energy Camera. Follow-up spectroscopy with the Gran Telescopio CANARIAS confirmed the nature of the system, with the lens being an early-type galaxy at a redshift of z=0.581 and the source being a starburst galaxy at z=1.165. Analysis of the system determined the Einstein radius to be 2.16 arcseconds and the total enclosed mass producing the lensing effect to be 1.86 ± 0.23 × 1012 solar masses.
Water vapour absorption_in_the_clear_atmosphere_of_a_neptune_sized_exoplanetSérgio Sacani
This document summarizes research on the transmission spectrum of the exoplanet HAT-P-11b, a Neptune-sized planet. Observations from the Hubble Space Telescope and Spitzer Space Telescope detected water vapor absorption in the planet's atmosphere at a wavelength of 1.4 micrometers. Analysis of the spectrum indicates the atmosphere is predominantly clear down to 1 mbar and has a hydrogen abundance similar to solar values. Atmospheric modeling suggests a metallicity around 190 times that of the Sun's, in agreement with core accretion planet formation theories. This makes HAT-P-11b the smallest exoplanet to date with a detected molecular signature in its atmosphere, providing new insights into the composition and formation of Neptune-sized
1) The document analyzes data from the SuperWASP-South telescope to classify four stars - VSX013997, 017283, 026353, and 091251.
2) The author cleaned the raw data, used Period04 to identify pulsation frequencies for each star, and created phased light curves to classify the stars.
3) Based on the periods, amplitudes, and light curve shapes, the author classified three stars as RRab subtype RR Lyrae variables and one star as a rotating ellipsoidal variable.
The document summarizes findings from orbital magnetic field measurements taken by the MESSENGER spacecraft around Mercury. Key points:
1) Remanent magnetization has been detected in Mercury's crust, providing evidence that Mercury had a dynamo-generated magnetic field early in its history.
2) The magnetization is estimated to have an average age of 3.7-3.9 billion years, based on its presence across diverse terrain including the youngest volcanic deposits on Mercury.
3) Ancient field strengths that could have produced the observed magnetization range from Mercury's current dipole field strength to values similar to Earth's ancient field.
Detection of a_supervoid_aligned_with_the_cold_spot_of_the_cosmic_microwave_b...Sérgio Sacani
This study uses infrared galaxy data from WISE and 2MASS surveys matched with optical data from the Pan-STARRS1 survey to search for a supervoid in the direction of the cosmic microwave background cold spot. Radial galaxy density profiles centered on the cold spot show a large underdensity extending over tens of degrees. Counts in photometric redshift bins within radii of 5 and 15 degrees show significantly low galaxy densities, at 5-6 sigma detection levels. This is consistent with a large 220 Mpc supervoid with an average density contrast of -0.14, centered at a redshift of 0.22. Such a supervoid could plausibly explain the observed cold spot in the cosmic microwave background.
A spectroscopic redshift_measurement_for_a_luminous_lyman_break_galaxy_at_z _...Sérgio Sacani
This document presents the spectroscopic confirmation of a luminous Lyman break galaxy (LBG) at a redshift of z = 7.7302 ± 0.0006, as observed using the MOSFIRE instrument on the Keck I telescope. The galaxy, named EGS-zs8-1, was pre-selected as a promising candidate for spectroscopic follow-up based on its bright apparent magnitude of H = 25.0 and very red Spitzer/IRAC colors suggestive of strong emission lines. Spectroscopic observations revealed a clear detection of the Lyman-alpha emission line at a observed wavelength of 1.06 microns, reliably confirming the high photometric redshift of z~7.7. Analysis of the
The broad lined_type_ic_sn_2012_ap_and_the_nature_of_relatvistic_supernovae_l...Sérgio Sacani
Artigo mostra como os astrônomos deduziram que a supernova SN 2012ap, é o elo perdido que faltava para a construção completa da árvore genealógica das supernovas.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
Small scatter and_nearly_isothermal_mass_profiles_to_four_half_light_radii_fr...Sérgio Sacani
This document summarizes the results of a study analyzing the total mass density profiles of 14 early-type galaxies using two-dimensional stellar kinematic data out to large radii of 2-6 half-light radii. The study finds that the total density profiles are well described by a nearly-isothermal power law with density proportional to radius from 0.1 to at least 4 half-light radii. The average logarithmic slope is -2.19 with a small scatter of only 0.11. This places tight constraints on galaxy formation models and illustrates the power of extended two-dimensional stellar kinematic observations.
The pillars of_creation_revisited_with_muse_gas_kinematics_and_high_mass_stel...Sérgio Sacani
The document discusses observations of the Pillars of Creation in the Eagle Nebula using integral field spectroscopy from the MUSE instrument on the VLT. For the first time, the study maps physical parameters like extinction, density, temperature, and velocity across the pillars. The data show that the pillar tips have high densities and are being photoevaporated by the massive stars in NGC 6611. The kinematics indicate a blueshifted photoevaporative flow, consistent with simulations. The 3D geometry of the pillars is inferred, with some in front of and some behind the ionizing stars. A previously unknown outflow is detected from the middle pillar, suggesting an embedded protostar.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
This document presents evidence that massive galaxies at redshift 2.2 (~3 billion years after the Big Bang) undergo an "inside-out quenching" process, where star formation is quenched first in the inner regions and later in the outer disks. High-resolution observations of 22 star-forming galaxies show that the most massive galaxies already have dense bulges similar to local spheroids, while still actively forming stars in their outer disks. The data suggests star formation is suppressed from the inside out on timescales of less than 1 Gyr in the centers and up to a few Gyr in the outer disks, as an "inside-out quenching wave" propagates through the galaxies. This provides insights into how
This document summarizes a study that identified 195 compact elliptical galaxies across different environments using data from optical and ultraviolet sky surveys. The researchers constructed the sample by selecting galaxies that were outliers from the universal color-magnitude relation and had small sizes and high stellar velocity dispersions based on spectral modeling. They found that 7 of the galaxies were isolated, not belonging to any known galaxy groups. For these isolated galaxies, the researchers identified possible host galaxies located up to 3.3 Mpc away. The stellar populations of the isolated compact elliptical galaxies were found to be similar to those in galaxy groups and clusters, suggesting a common formation mechanism.
Four new planets_around_giant_stars_and_the_mass_metallicity_correlation_of_p...Sérgio Sacani
Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets.
In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and
that their fraction increases with the stellar mass.
Aims. During the past six years, we have conducted a radial velocity follow-up program of 166 giant stars, to detect substellar
companions, and characterizing their orbital properties. Using this information, we aim to study the role of the stellar evolution in
the orbital parameters of the companions, and to unveil possible correlations between the stellar properties and the occurrence rate of
giant planets.
Methods. We have taken multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we have computed
precision radial velocities and we have derived atmospheric and physical parameters. Additionally, velocities computed from UCLES
spectra are presented here. By studying the periodic radial velocity signals, we have detected the presence of several substellar
companions.
Results. We present four new planetary systems around the giant stars HIP8541, HIP74890, HIP84056 and HIP95124. Additionally,
we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that
giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5
−5.9 % around stars with [Fe/H] ∼
0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆∼ 1.0 - 2.1 M⊙ ,
with a maximum of f = 13.0+10.1
−4.2 %, at M⋆= 2.1 M⊙ .
Conclusions. We conclude that giant planets are preferentially formed around metal-rich stars. Also, we conclude that they are more
efficiently formed around more massive stars, in the stellar mass range of ∼ 1.0 - 2.1 M⊙ . These observational results confirm previous
findings for solar-type and post-MS hosting stars, and provide further support to the core-accretion formation model.
This document summarizes an 8-year survey using the HARPS spectrograph to detect super-Earth and Neptune-mass planets around solar-type stars. Over 50% of solar-type stars were found to harbor at least one planet within 100 days. The mass distribution of super-Earths and Neptune-mass planets increases sharply from 30-15 Earth masses. Most of these planets belong to multi-planetary systems and have orbital eccentricities under 0.45. In contrast, giant planets are more common around metal-rich stars and can have eccentricities over 0.9. The precision of HARPS enables detection of planets in the habitable zones of solar-type stars.
Artigo que descreve a descoberta do exoplaneta Kepler-432b, um exoplaneta mais massivo que Júpiter que orbita uma estrela gigante vermelha bem próximo e numa órbita extremamente alongada.
A rock composition_for_earth_sized_exoplanetsSérgio Sacani
1) Researchers measured the mass of Kepler-78b, an Earth-sized exoplanet orbiting its host star every 8.5 hours, to be 1.69 ± 0.41 M⊕ using Doppler spectroscopy of the star's radial velocity variations.
2) Given the planet's radius of 1.20 ± 0.09 R⊕, its mean density of 5.3 ± 1.8 g/cm3 is similar to Earth's, suggesting a rocky composition of iron and rock.
3) Kepler-78b is the smallest exoplanet yet characterized with both an accurate mass and radius measurement, extending measurements of planetary composition into the size range of Earth and Venus.
Mapping the complex_kinematics_of_l_lobjects_in_the_orion_nebulaSérgio Sacani
This document presents a study of the kinematics of two LL Orionis-type objects (LL objects) in the Orion nebula, LL 1 and LL 2, and their associated Herbig-Haro jets HH 888 and HH 505. The authors combine long-slit spectroscopic observations of the objects with proper motion measurements to construct 3D velocity maps. The maps reveal:
1) Low velocities (10-20 km/s) in the stellar bowshocks of LL 1 and LL 2, with LL 1 showing symmetric motions and LL 2 showing asymmetric motions following nebula gradients.
2) Jet knot velocities over 200 km/s near the stars declining to under 100 km/s farther out in HH 8
Hubble Space Telescope Observations of NGC 253 Dwarf Satellites: Three Ultra-...Sérgio Sacani
We present deep Hubble Space Telescope (HST) imaging of five faint dwarf galaxies associated with the nearby
spiral NGC 253 (D ≈ 3.5 Mpc). Three of these are newly discovered dwarf galaxies, while all five were found in
the Panoramic Imaging Survey of Centaurus and Sculptor, a Magellan+Megacam survey to identify faint dwarfs
and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data
reach 3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances,
structural parameters, and luminosities. All five systems contain mostly old, metal-poor stellar populations
(age ∼12 Gyr, [M/H] −1.5) and have sizes (rh ∼ 110–3000 pc) and luminosities (MV ∼ −7 to −12 mag) largely
consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered
beyond the Local Group. We also use archival H I data to place limits on the gas content of our discoveries. Deep
imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity
function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come
A nearby m_star_with_three_transiting_super-earths_discovered_by_k2Sérgio Sacani
This document reports the discovery of three transiting super-Earth planets orbiting a nearby bright M0 dwarf star, EPIC 201367065, using data from the K2 mission. Photometry from K2 reveals three planetary candidates with orbital periods of 10.056, 24.641, and ~45 days and radii between 1.5-2.1 Earth radii. Spectroscopy of the host star determines it has a mass of 0.601 solar masses, radius of 0.561 solar radii, and is located about 45 parsecs away, making the planets some of the coolest small planets known around a nearby star. The system presents an opportunity to measure the planet masses and constrain atmospheric compositions via future observations
Validation of twelve_small_kepler_transiting_planets_in_the_habitable_zoneSérgio Sacani
Artigo descreve a análise dos mais novos exoplanetas descobertos pela missão Kepler, incluindo o Kepler-438b, o exoplaneta mais parecido com a Terra já descoberto até o momento.
The Sparkler: Evolved High-redshift Globular Cluster Candidates Captured by JWSTSérgio Sacani
This document discusses compact red sources detected around a strongly lensed galaxy ("the Sparkler") at a redshift of 1.378 using JWST data. Photometry and morphological fits of the sources suggest they are spatially unresolved, very red, and consistent with old stellar populations. Spectroscopy shows emission from the galaxy but no signs of star formation in the red sources. The sources are most likely evolved globular clusters dating back to formation redshifts between 7-11, corresponding to ages of 3.9-4.1 billion years at the time of observation. If confirmed, these would be the first observed globular clusters at high redshift, opening a window into early globular cluster formation in the first billion years of
This document describes observations of Cepheid variables in the host galaxies of two Type Ia supernovae, SN 1995al in NGC 3021 and SN 2002fk in NGC 1309, using the Hubble Space Telescope. The observations aim to increase the sample of reliably calibrated supernovae to improve the measurement of the Hubble constant. New Cepheids were discovered, including many with periods over 60 days. Metallicity measurements of the galaxies' H II regions were also consistent with solar metallicity. The new data on the supernovae and Cepheids will help strengthen the distance ladder and reduce systematic uncertainties in the determination of the Hubble constant.
Chiotelis Ioannis, Theodoropoulou Maria, “Searching for Black Holes. Photometry in our Classrooms”, Hellenic Conference on Innovating STEM Education, 16-18 December 2016, Athens, Greece.
No xrays from_wasp18_implications_for_its_age_activity_and_influenceSérgio Sacani
1) An 87 ks Chandra observation was performed of the star WASP-18, which hosts a very close-in hot Jupiter planet orbiting within 20 hours.
2) WASP-18 was not detected in X-rays down to a luminosity limit of 4 x 10^26 erg/s, over two orders of magnitude lower than expected for a star of its estimated age of 600 Myr.
3) This unusually low activity level for a star of WASP-18's age and mass suggests that the massive planet may play a role in disrupting the stellar magnetic dynamo generated within its thin convective layers through star-planet interaction.
WASP-18: NASA's Chandra X-ray Observatory Finds Planet That Makes Star Act De...GOASA
This document summarizes a study observing the star WASP-18 and its hot Jupiter planet using the Chandra X-ray Observatory. The star was not detected in X-rays down to a luminosity limit much lower than expected for its estimated age of 600 million years. This suggests unusual lack of magnetic activity, which the authors argue may be due to disruption of the stellar dynamo by the massive planet in its close orbit. Over 200 other X-ray sources were also detected in the Chandra image and are listed. The non-detection of X-rays from WASP-18 has implications for models of star-planet interaction and the evolutionary stage of this system.
Is Betelgeuse Really Rotating? Synthetic ALMA Observations of Large-scale Con...Sérgio Sacani
The evolved stages of massive stars are poorly understood, but invaluable constraints can be derived from spatially resolved observations of nearby red supergiants, such as Betelgeuse. Atacama Large Millimeter/submillimeter Array (ALMA) observations of Betelgeuse showing a dipolar velocity field have been interpreted as evidence for a projected rotation rate of about 5 km s−1. This is 2 orders of magnitude larger than predicted by single-star evolution, which led to suggestions that Betelgeuse is a binary merger. We propose instead that large-scale convective motions can mimic rotation, especially if they are only partially resolved. We support this claim with 3D CO5BOLDsimulations of nonrotating red supergiants that we postprocessed to predict ALMA images and SiO spectra. We show that our synthetic radial velocity maps have a 90% chance of being falsely interpreted as evidence for a projected rotation rate of 2 km s−1 or larger for our fiducial simulation. We conclude that we need at least another ALMA observation to firmly establish whether Betelgeuse is indeed rapidly rotating. Such observations would also provide insight into the role of angular momentum and binary interaction in the late evolutionary stages. The data will further probe the structure and complex physical processes in the atmospheres of red supergiants, which are immediate progenitors of supernovae and are believed to be essential in the formation of gravitational-wave sources.
This document summarizes the discovery of a fourth planet orbiting the red dwarf star GJ 581. The planet, called GJ 581e, has a minimum mass of 1.9 Earth masses and orbits with a period of 3.15 days, making it the innermost planet in the system. Updated radial velocity measurements also allowed the researchers to correct the orbital period of the outermost planet GJ 581d, determining it to be 66.8 days rather than the previously reported 83 days. This revised period places GJ 581d within the star's habitable zone. The researchers conclude the GJ 581 system has 4 planets, with the detection of GJ 581e being the lowest mass exoplanet
This summarizes a scientific study on long-distance quantum teleportation between two laboratories separated by 55 meters but connected by 2 kilometers of fiber optic cable. The key points are:
1) Researchers teleported quantum states (qubits) carried by photons at 1.3 micrometer wavelengths onto photons at 1.55 micrometer wavelengths between the two laboratories.
2) The qubits were encoded in time-bin superpositions and entanglement rather than polarization to make them more robust against decoherence in optical fibers.
3) A partial Bell state measurement was performed using linear optics at the receiving end to probabilistically teleport the quantum states over the long distance.
A dynamical signature_of_multiple_stellar_populations_in_47_tucanaeSérgio Sacani
The document analyzes proper motion data from Hubble Space Telescope images of the globular cluster 47 Tucanae taken over 10 years. It finds differing proper motion anisotropies between the bluest and reddest main sequence stars in 47 Tucanae, suggesting different kinematic properties for the different stellar populations. The bluest stars also exhibit the strongest central concentration. These results provide dynamical evidence for multiple stellar populations in 47 Tucanae and implications for their formation scenarios.
LHS 475 b: A Venus-sized Planet Orbiting a Nearby M DwarfSérgio Sacani
Based on photometric observations by TESS, we present the discovery of a Venussized planet transiting LHS 475, an M3 dwarf located 12.5 pc from the Sun. The mass
of the star is 0.274 ± 0.015 M. The planet, originally reported as TOI 910.01, has an
orbital period of 2.0291025 ± 0.0000020 days and an estimated radius of 0.955 ± 0.053
R⊕. We confirm the validity and source of the transit signal with MEarth ground-based
follow-up photometry of five individual transits. We present radial velocity data from
CHIRON that rule out massive companions. In accordance with the observed massradius distribution of exoplanets as well as planet formation theory, we expect this
Venus-sized companion to be terrestrial, with an estimated RV semi-amplitude close to
1.0 m/s. LHS 475 b is likely too hot to be habitable but is a suitable candidate for
emission and transmission spectroscopy.
The Lyα Reference Sample. XIV. Lyα Imaging of 45 Low-redshift Star-forming Ga...Sérgio Sacani
We present Lyα imaging of 45 low-redshift star-forming galaxies observed with the Hubble Space Telescope. The
galaxies have been selected to have moderate to high star formation rates (SFRs) using far-ultraviolet (FUV)
luminosity and Hα equivalent width criteria, but no constraints on Lyα luminosity. We employ a pixel stellar
continuum fitting code to obtain accurate continuum-subtracted Lyα, Hα, and Hβ maps. We find that Lyα is less
concentrated than FUV and optical line emission in almost all galaxies with significant Lyα emission. We present
global measurements of Lyα and other quantities measured in apertures designed to capture all of the Lyα
emission. We then show how the escape fraction of Lyα relates to a number of other measured quantities (mass,
metallicity, star formation, ionization parameter, and extinction). We find that the escape fraction is strongly
anticorrelated with nebular and stellar extinction, weakly anticorrelated with stellar mass, but no conclusive
evidence for correlations with other quantities. We show that Lyα escape fractions are inconsistent with common
dust extinction laws, and discuss how a combination of radiative transfer effects and clumpy dust models can help
resolve the discrepancies. We present an SFR calibration based on Lyα luminosity, where the equivalent width of
Lyα is used to correct for nonunity escape fraction, and show that this relation provides a reasonably accurate SFR
estimate. We also show stacked growth curves of Lyα for the galaxies that can be used to find aperture loss
fractions at a given physical radius.
Similar to Hats 6b a_warm_saturn_transiting_an_early_m_dwarf_star_and_a_set_of_empirical_relations_for_characterizing_m_and_k_dwarfs_planet_hosts (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Travis Hills' Endeavors in Minnesota: Fostering Environmental and Economic Pr...Travis Hills MN
Travis Hills of Minnesota developed a method to convert waste into high-value dry fertilizer, significantly enriching soil quality. By providing farmers with a valuable resource derived from waste, Travis Hills helps enhance farm profitability while promoting environmental stewardship. Travis Hills' sustainable practices lead to cost savings and increased revenue for farmers by improving resource efficiency and reducing waste.
1. arXiv:1408.1758v1[astro-ph.EP]8Aug2014
Draft version August 11, 2014
Preprint typeset using LATEX style emulateapj v. 5/2/11
HATS-6b: A WARM SATURN TRANSITING AN EARLY M DWARF STAR, AND A SET OF EMPIRICAL
RELATIONS FOR CHARACTERIZING K AND M DWARF PLANET HOSTS †
J. D. Hartman1
, D. Bayliss2
, R. Brahm3,4
, G. ´A. Bakos1,⋆,⋆⋆
, L. Mancini5
, A. Jord´an3,4
, K. Penev1
, M. Rabus3,5
,
G. Zhou2
, R. P. Butler6
, N. Espinoza3,4
, M. de Val-Borro1
, W. Bhatti1
, Z. Csubry1
, S. Ciceri5
, T. Henning5
,
B. Schmidt2
, P. Arriagada6
, S. Shectman7
, J. Crane7
, I. Thompson7
, V. Suc3
, B. Cs´ak5
, T. G. Tan8
,
R. W. Noyes9
, J. L´az´ar10
, I. Papp10
, P. S´ari10
Draft version August 11, 2014
ABSTRACT
We report the discovery by the HATSouth survey of HATS-6b, an extrasolar planet transiting a
V=15.2 mag, i = 13.7 mag M1V star with a mass of 0.57 M⊙ and a radius of 0.57 R⊙. HATS-6b has
a period of P ≈ 3.3253d, mass of Mp ≈ 0.32 MJ, radius of Rp ≈ 1.00 RJ, and zero-albedo equilibrium
temperature of Teq = 712.8±5.1K. HATS-6 is one of the lowest mass stars known to host a close-in gas
giant planet, and its transits are among the deepest of any known transiting planet system. We discuss
the follow-up opportunities afforded by this system, noting that despite the faintness of the host star,
it is expected to have the highest K-band S/N transmission spectrum among known gas giant planets
with Teq < 750 K. In order to characterize the star we present a new set of empirical relations between
the density, radius, mass, bolometric magnitude, and V , J, H and K-band bolometric corrections for
main sequence stars with M < 0.80 M⊙, or spectral types later than K5. These relations are calibrated
using eclipsing binary components as well as members of resolved binary systems. We account for
intrinsic scatter in the relations in a self-consistent manner. We show that from the transit-based
stellar density alone it is possible to measure the mass and radius of a ∼ 0.6 M⊙ star to ∼ 7% and
∼ 2% precision, respectively. Incorporating additional information, such as the V − K color, or an
absolute magnitude, allows the precision to be improved by up to a factor of two.
Subject headings: planetary systems — stars: individual (HATS-6) techniques: spectroscopic, photo-
metric
1. INTRODUCTION
One of the goals in the study of exoplanetary systems
is to determine how the properties of planets depend on
1 Department of Astrophysical Sciences, Princeton University,
NJ 08544, USA; email: jhartman@astro.princeton.edu
2 The Australian National University, Canberra, Australia
3 Instituto de Astrof´ısica, Facultad de F´ısica, Pontificia Uni-
versidad Cat´olica de Chile, Av. Vicu˜na Mackenna 4860, 7820436
Macul, Santiago, Chile
4 Millennium Institute of Astrophysics, Av. Vicu˜na Mackenna
4860, 7820436 Macul, Santiago, Chile
5 Max Planck Institute for Astronomy, Heidelberg, Germany
6 Department of Terrestrial Magnetism, Carnegie Institution
of Washington, 5241 Broad Branch Road NW, Washington, DC
20015-1305, USA
7 The Observatories of the Carnegie Institution of Washing-
ton, 813 Santa Barbara Street, Pasadena, CA 91101, USA
8 Perth Exoplanet Survey Telescope, Perth, Australia
9 Harvard-Smithsonian Center for Astrophysics, Cambridge,
MA, USA
10 Hungarian Astronomical Association, Budapest, Hungary
⋆ Alfred P. Sloan Research Fellow
⋆⋆ Packard Fellow
† The HATSouth network is operated by a collaboration con-
sisting of Princeton University (PU), the Max Planck Insti-
tute f¨ur Astronomie (MPIA), the Australian National Univer-
sity (ANU), and the Pontificia Universidad Cat´olica de Chile
(PUC). The station at Las Campanas Observatory (LCO) of the
Carnegie Institute is operated by PU in conjunction with PUC,
the station at the High Energy Spectroscopic Survey (H.E.S.S.)
site is operated in conjunction with MPIA, and the station at
Siding Spring Observatory (SSO) is operated jointly with ANU.
This paper includes data gathered with the 6.5 m Magellan Tele-
scopes located as Las Campanas Observatory, Chile. Based in
part on observations made with the MPG 2.2 m Telescope and
the ESO 3.6 m Telescope at the ESO Observatory in La Silla.
This paper uses observations obtained with facilities of the Las
Cumbres Observatory Global Telescope.
the properties of their host stars. An important parame-
ter in this respect is the host star mass. Results from
both radial velocity and transit surveys indicate that
the occurrence rate of gas giant planets is a steep func-
tion of stellar mass scaling approximately as N ∝ M⋆
(Johnson et al. 2010) for main sequence stars of type M
through F (smaller planets, on the other hand, appear to
be more frequent around M dwarfs than around hotter
stars, Howard et al. 2012). The low occurrence rate of
these planets around M dwarfs, coupled with the fact
that most surveys primarily target FGK dwarf stars,
means that only one hot Jupiter has so far been dis-
covered around an M0 dwarf (Kepler-45; Johnson et al.
2012), and only a handful of others have been found
around very late K dwarf stars (WASP-80, Triaud et al.
2013b; WASP-43, Hellier et al. 2011; and HAT-P-54,
Bakos et al. 2014, being the only three known transiting-
hot-Jupiter-hosting K dwarfs with M < 0.65 M⊙).
In addition to enabling the study of planetary proper-
ties as a function of stellar mass, finding planets around
late-type stars has at least two other advantages. The
small sizes of these stars coupled with their low luminosi-
ties means that a planet with a given radius and orbital
period around a late-type star will produce deeper tran-
sits and have a cooler equilibrium temperature than if
it were around a larger star. This makes planets around
late-type stars attractive targets for carrying out detailed
follow-up observations, such as atmospheric characteri-
zations. A second, perhaps under appreciated, advan-
tage of these stars is that they are remarkably simple
in their bulk properties. Whereas, due to stellar evo-
lution, the radius of a solar-metallicity, solar-mass star
2. 2 Hartman et al.
varies by ∼ 40% over the 10 Gyr age of the Galactic disk,
the radius of a 0.6 M⊙ star varies by less than ∼ 5%
over the same time-span. The parameters of low-mass
stars follow tight main-sequence relations, enabling high-
precision measurements of their properties from only a
single (or a few) observable(s). The precision of the stel-
lar parameters feeds directly into the precision of the
planetary parameters, so that in principle planets around
low-mass stars may be characterized with higher preci-
sion than those around higher mass stars.
Here we present the discovery of a transiting, short-
period, gas-giant planet around an M1 dwarf star. This
planet, HATS-6b, was discovered by the HATSouth sur-
vey, a global network of fully-automated wide-field pho-
tometric instruments searching for transiting planets
(Bakos et al. 2013). HATSouth uses larger-diameter op-
tics than other similar projects allowing an enhanced sen-
sitivity to faint K and M dwarfs.
We also present a new set of empirical relations to use
in characterizing the properties of transiting planet host
stars with M < 0.80 M⊙. While there has been much
discussion in the literature of the apparent discrepancy
between observations and various theoretical models for
these stars (e.g., Torres & Ribas 2002; Ribas 2003; Torres
2013; Zhou et al. 2014, and references therein), the grow-
ing set of well-characterized low-mass stars has revealed
that, as expected, these stars do follow tight main se-
quence relations. We show that from the bulk density of
the star alone, which is determined from the transit light
curve and RV observations, it is possible to measure the
mass and radius of a ∼ 0.6 M⊙ star to ∼ 7% and ∼ 2%
precision, respectively. Incorporating additional infor-
mation, such as the V − K color, or an absolute magni-
tude, allows the precision to be improved by a factor of
two.
The layout of the paper is as follows. In Section 2 we
report the detection of the photometric signal and the
follow-up spectroscopic and photometric observations of
HATS-6. In Section 3 we describe the analysis of the
data, beginning with ruling out false positive scenarios,
continuing with our global modelling of the photometry
and radial velocities, and finishing with the determina-
tion of the stellar parameters, and planetary parame-
ters which depend on them, using both theoretical stellar
models as well as the empirical relations which we derive
here. Our findings are discussed in Section 4.
2. OBSERVATIONS
2.1. Photometric detection
Observations of a field containing HATS-6 (see Ta-
ble 9 for identifying information) were carried out with
the HS-2, HS-4 and HS-6 units of the HATSouth net-
work (located at Las Campanas Observatory in Chile,
the H.E.S.S. gamma-ray telescope site in Namibia, and
Siding Spring Observatory in Australia, respectively; see
Bakos et al. 2013 for a detailed description of the HAT-
South network) between UT 2009-09-17 and UT 2010-
09-10. A total 5695, 5544 and 88 images included in our
final trend and outlier-filtered light curves were obtained
with HS-2, HS-4 and HS-6, respectively. Observations
were made through a Sloan r filter, using an exposure
time of 240 s and a median cadence of 293 s (see also
Table 1).
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
-0.4 -0.2 0 0.2 0.4
∆mag
Orbital phase
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
-0.06 -0.04 -0.02 0 0.02 0.04 0.06
∆mag
Orbital phase
Fig. 1.— Unbinned instrumental r-band light curve of HATS-
6 folded with the period P = 3.3252725 days resulting from the
global fit described in Section 3. The solid line shows the best-fit
transit model (see Section 3). In the lower panel we zoom-in on
the transit; the dark filled points here show the light curve binned
in phase using a bin-size of 0.002.
The data were reduced to trend-filtered light curves
following Bakos et al. (2013). We apply two empirical
trend filtering techniques to the data. The first is to
decorrelate the light curves against a set of measured
parameters which vary from image to image, including
the X and Y sub-pixel coordinates of the star, three pa-
rameters describing the shape of the image point spread
function, the hour angle of the observations, the zenith
distance, and the sky background near the target. We
refer to this filtering as External Parameter Decorrela-
tion (EPD; Bakos et al. 2010). The second filtering tech-
nique is to use the Trend Filtering Algorithm (TFA) due
to Kov´acs et al. (2005). In this method we select a list
of ∼ 800 template light curves uniformly distributed in
position across the field, and coming from stars with a
broad range of magnitudes. We then fit the EPD-filtered
light curve for HATS-6 as a linear combination of these
∼ 800 templates, and subtract the fit from the observa-
tions. The filtered light curve for HATS-6 has a point-to-
point RMS of 0.02 mag and is dominated by noise from
the background sky. Transits were identified in the re-
sulting HATSouth light curve of HATS-6 using the Box
Least Squares (BLS; Kov´acs et al. 2002) algorithm. Fig-
ure 1 shows the phase-folded HATSouth light curve of
HATS-6 together with our best-fit transit model, while
the photometric measurements are provided in Table 2.
We searched the residual HATSouth light curve for
additional transit signals using BLS but found no sig-
nificant detection. We also searched for continuous
quasi-periodic variability using both the Discrete Fourier
Transform (Kurtz 1985) and the Discrete Autocorrela-
tion Function (Edelson & Krolik 1988). We find a pos-
sible signal in the pre-TFA light curve with a period of
P = 35.1 d and an S/N, measured in the power spectrum,
of 12.3. This signal is not seen in the Autocorrelation
Function, nor is it seen in the light curve after processing
with TFA. While potentially due to stellar rotation, this
may also be time-correlated noise. We therefore do not
claim a measurement of the photometric rotation period
for this star.
2.2. Photometric follow-up
In order to confirm the transit signal, and determine
the parameters of the system with better accuracy, we
3. HATS-6b 3
0
0.1
0.2
0.3
0.4
0.5
0.6
-0.15 -0.1 -0.05 0 0.05 0.1 0.15
∆(mag)-Arbitraryoffsets
Time from transit center (days)
RC-band
RC
RC
zs
i
z
RC
2013 Feb 17 - PEST
2013 Feb 27 - PEST
2013 Mar 29 - PEST
2013 Nov 23 - LCOGT 1m
2013 Dec 7 - LCOGT 1m
2012 Sep 3 - CTIO 0.9m
2013 Oct 27 - CTIO 0.9m
-0.1 -0.05 0 0.05 0.1
Time from transit center (days)
2013 Feb 17 - PEST
2013 Feb 27 - PEST
2013 Mar 29 - PEST
2013 Nov 23 - LCOGT 1m
2013 Dec 7 - LCOGT 1m
2012 Sep 3 - CTIO 0.9m
2013 Oct 27 - CTIO 0.9m
Fig. 2.— Left: Unbinned follow-up transit light curves of HATS-6. The dates, filters and instruments used for each event are indicated.
The light curves have been detrended using the EPD process. Curves after the first are shifted for clarity. Our best fit is shown by the solid
lines. Right: Residuals from the fits in the same order as the curves at left. Additional follow-up light curves from GROND are shown in
Figure 3.
carried out follow-up photometric observations of HATS-
6 using the 0.3 m Perth Exoplanet Survey Telescope
(PEST), the CTIO 0.9 m, telescopes in the LCOGT
1 m network (Brown et al. 2013), and GROND on the
MPG 2.2 m (Greiner et al. 2008). Key aspects of these
observations, including the dates of the observations, the
number of images obtained, the cadence, filter used, and
the precision of the resulting HATS-6 light curves, as
measured from the RMS of the residuals from our best-fit
model, are summarized in Table 1. The light curves are
plotted in Figures 2 and 3, while the measurements are
provided in Table 2. Details regarding the PEST instru-
ment, our observational procedure, as well as our reduc-
tion and photometry methods can be found in Zhou et al.
(2014); see Penev et al. (2013) and Mohler-Fischer et al.
(2013) for similar information regarding the GROND ob-
servations. Because this is the first time we have used the
CTIO 0.9 m and the LCOGT 1 m network, we describe
our use of these facilities in more detail below.
On the nights of 2012 Sep. 3 and 2013 Oct. 27, we
performed photometric observations of HATS-6 using
the CTIO 0.9 m telescope, which has a CCD with a
13.′
6 × 13.′
6 field of view. On the first night we used a
Gunn z′
filter and on the latter one a Kron-Cousins RC
filter. We defocused the telescope in order to broaden
the point spread function. Images from both nights were
calibrated (bias subtracted and flat fielded) with custom
Python routines. A fringing effect was seen in the images
taken during our full moon night in z-band. However,
images taken with the RC filter did not show fringing.
Therefore, we also took 53 empty field regions with the
Gunn z′
filter during our 2012 Sep. CTIO run. We com-
bined these images and subtracted the sky background,
and then scaled the combined image to match, and re-
move, the additive fringing effect seen in the science im-
ages. To reduce the calibrated images to light curves,
we chose a reference image and calculated the shift of all
images with respect to the reference image. From the
reference image we extracted the position of the stars.
Following Deeg & Doyle (2001), the time series photom-
etry was generated from these observations using opti-
mized aperture photometry that maximizes the signal-
to-noise ratio (S/N) for each star. For all images in one
night we used three fixed apertures and choose these to
be much larger than the typical point spread function in
order to minimize the impact of the time-variable point
spread functions. The resulting light curves of HATS-6
have precisions of 4.7 mmag and 3.7 mmag on the first
and second nights, respectively.
Observations of HATS-6 were carried out using the
LCOGT 1 m network on the UT nights of 2013-11-23 and
2013-12-07. We used one of the three telescopes installed
at the South African Astronomical Observatory (SAAO)
on the night of 2013-11-23, and one of the telescopes at
CTIO on the night of 2013-12-07. In both cases we used
the SBIG STX-16803 4K×4K imagers with which the
telescopes were initially deployed. These imagers pro-
vided a 16′
× 16′
field of view with a pixel scale of 0.′′
23.
We used a Pan-STARSS zS filter for the first night, and
a Sloan i′
filter for the second night. Other details re-
4. 4 Hartman et al.
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
-0.1 -0.05 0 0.05 0.1
∆(mag)
Time from transit center (days)
i-band
2014 Mar 6 - GROND/MPG 2.2m
-0.05 0 0.05 0.1
Time from transit center (days)
z-band
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
∆(mag) g-band r-band
Fig. 3.— Unbinned instrumental Sloan g-, r-, i- and z-band transit light curves of HATS-6 obtained with GROND on the MPG 2.2 m
on the night of UT 2014 March 6. The light curves have been detrended using the EPD process, and the best-fit is shown by the solid
lines. Below each light curve we plot the residuals.
garding the instrumentation can be found in Brown et al.
(2013). Calibrated science images were provided by the
LCOGT 1 m pipeline. We performed astrometry and
aperture photometry using tools from the FITSH pack-
age (P´al 2012) on these images following methods that we
have previously applied to observations from the Faulkes
Telescopes, North and South, as well as to observations
from Keplercam on the Fred Lawrence Whipple Obser-
vatory 1.2 m telescope. This procedure is described in
Bakos et al. (2010).
2.3. Spectroscopy
Table 3 summarizes the follow-up spectroscopic obser-
vations which we obtained for HATS-6.
2.3.1. Reconnaissance Spectroscopy
Initial reconnaissance spectroscopic observations of
HATS-6 were carried out using the Wide Field Spec-
trograph (WiFeS; Dopita et al. 2007) on the ANU 2.3 m
telescope at SSO together with the Echelle spectrograph
on the du Pont 2.5 m telescope at LCO. The ANU 2.3 m
data were reduced and analyzed following Bayliss et al.
(2013), while for the du Pont data we used the pipeline
we have previously developed (Jord´an et al. 2014) to an-
alyze data from the Coralie and FEROS spectrographs,
adapted for the different spectral format of the instru-
ment. A single WiFeS spectrum was obtained with a
resolution of R ≡ λ/∆λ = 3000 to use in measuring the
effective temperature, surface gravity, and metallicity of
the star, while four observations were obtained at a reso-
lution of R = 7000 to check for RV variations with ampli-
tude 5 km s−1
that would indicate that the transiting
companion is of stellar mass. The two du Pont spectra
each had a resolution of R = 40000 covering a wave-
length range of 3700–7000˚A, and were used to measure
the effective temperature, gravity, metallicity, projected
rotation velocity and radial velocity of the star. Like the
WiFeS spectra, the RV precision of the du Pont observa-
tions (∼ 500 m s−1
) is not high enough to detect velocity
variations due to a planet, but is sufficient to rule out
stellar-mass companions.
Our analysis of the R = 3000 WiFeS spectrum indi-
cated an effective temperature of Teff⋆ = 3600 ± 300 K,
while the du Pont spectra yielded Teff⋆ = 3700 ± 100 K.
This effective temperature corresponds to a spectral type
of M1 (Rajpurohit et al. 2013). The spectrum shows
clear TiO absorption bands, and is consistent with an
M1V spectral classification. This spectrum also shows
that HATS-6 is a quiet M-dwarf, with no evidence of
emission in the Hα or Ca II H and K line cores. Addi-
tional indications that HATS-6 is a quiet star are the lack
of any obvious star-spot crossing events in the photomet-
ric follow-up light curves (Figures 2 and 3), and the lack
of large-amplitude photometric variability in the HAT-
South light curve. The WiFeS spectrum also indicated a
dwarf-like surface gravity (log g⋆ = 3.9±0.3; c.g.s. units)
and a possibly sub-solar metallicity ([Fe/H]= −1.0±0.5),
while our analysis of the du Pont spectra yielded a some-
5. HATS-6b 5
TABLE 1
Summary of photometric observations
Facility Date(s) Number of Images a Cadence (s) b Filter Precision (mmag)
HS-2 2009 Sep–2010 Sep 5695 295 r 21.3
HS-4 2009 Sep–2010 Sep 5544 293 r 21.0
HS-6 2010 Aug–2010 Sep 88 296 r 18.6
CTIO 0.9 m 2012 Sep 03 34 297 z 4.7
PEST 0.3 m 2013 Feb 17 58 205 R 6.1
PEST 0.3 m 2013 Feb 27 53 131 R 5.6
PEST 0.3 m 2013 Mar 29 24 261 R 4.8
CTIO 0.9 m 2013 Oct 27 99 181 RC 3.7
LCOGT 1 m 2013 Nov 23 48 76 z 4.2
LCOGT 1 m 2013 Dec 07 149 74 i 3.8
GROND/MPG 2.2 m 2014 Mar 06 95 155 g 1.8
GROND/MPG 2.2 m 2014 Mar 06 95 155 r 1.1
GROND/MPG 2.2 m 2014 Mar 06 95 155 i 1.1
GROND/MPG 2.2 m 2014 Mar 06 95 155 z 1.1
a Excludes images which were rejected as significant outliers in the fitting procedure.
b The mode time difference rounded to the nearest second between consecutive points in each light curve. Due to visibility,
weather, pauses for focusing, etc., none of the light curves have perfectly uniform time sampling.
TABLE 2
Differential photometry of HATS-6
BJD Maga σMag Mag(orig)b Filter Instrument
(2 400 000+)
55185.60957 −0.00387 0.01084 · · · r HS
55145.70640 −0.07475 0.03251 · · · r HS
55095.82750 −0.01258 0.01255 · · · r HS
55275.39406 0.02245 0.01229 · · · r HS
55195.58763 −0.00021 0.01587 · · · r HS
55182.28728 0.00324 0.01174 · · · r HS
55145.70968 −0.00768 0.02964 · · · r HS
55185.61296 0.02073 0.01078 · · · r HS
55095.83089 −0.02280 0.01379 · · · r HS
55105.80688 −0.02863 0.02168 · · · r HS
Note. — This table is available in a machine-readable form in the online journal.
A portion is shown here for guidance regarding its form and content. The data are
also available on the HATSouth website at http://www.hatsouth.org.
a The out-of-transit level has been subtracted. For the HATSouth light curve (rows
with “HS” in the Instrument column), these magnitudes have been detrended using
the EPD and TFA procedures prior to fitting a transit model to the light curve.
Primarily as a result of this detrending, but also due to blending from neighbors, the
apparent HATSouth transit depth is somewhat shallower than that of the true depth
in the Sloan r filter (the apparent depth is 90% that of the true depth). For the
follow-up light curves (rows with an Instrument other than “HS”) these magnitudes
have been detrended with the EPD procedure, carried out simultaneously with the
transit fit (the transit shape is preserved in this process).
b Raw magnitude values without application of the EPD procedure. This is only
reported for the follow-up light curves.
what lower surface gravity (log g⋆ = 3.2±0.5) and metal-
licity ([Fe/H]= −1.5 ± 0.5) and a moderately high rota-
tion velocity (v sin i = 7.5 ± 2.0 km s−1
). The analysis,
however, relies on synthetic templates (MARCS models
in the case of WiFeS and models from Coelho et al. 2005
in the case of du Pont) which are known to be unre-
liable for M type stars. This means that systematic er-
rors in the determined parameters are most likely greater
than the estimated uncertainties (especially when Teff⋆,
log g⋆ and [Fe/H], which are strongly correlated with each
other, are all allowed to vary in fitting the spectra). As
an example of this, note that based on the Dartmouth
single stellar evolution models (Dotter et al. 2008) the
minimum surface gravity realized for a Teff⋆ = 3700 K
dwarf star within 13.8 Gyr is log g⋆ = 4.73 which is signif-
icantly higher than the values determined from the spec-
troscopic modelling (the only evolved single stars that
reach Teff⋆ = 3700K have log g⋆ 2). We therefore do
not consider the log g⋆ [Fe/H], or v sin i measurements
from this analysis to be reliable. More reliable estimate
of Teff⋆ and [Fe/H] are presented in the next section.
2.3.2. Confirmation Spectroscopy
In order to confirm HATS-6 as a transiting planet sys-
tem through a detection of the RV orbital variation we
obtained high-resolution spectra with three facilities ca-
pable of achieving ∼ 10 m s−1
or better RV precision.
These are the FEROS spectrograph (Kaufer & Pasquini
1998) on the MPG 2.2 m telescope at La Silla Obser-
vatory (LSO), the Planet Finder Spectrograph (PFS;
Crane et al. 2010) on the Magellan Clay 6.5 m telescope
at LCO, and the High Accuracy Radial Velocity Planet
6. 6 Hartman et al.
Searcher (HARPS; Mayor et al. 2003) spectrograph on
the ESO 3.6 m telescope at LSO. Figure 4 shows the
phased RV measurements and bisector spans from these
observations, together with our best-fit orbit, while Ta-
ble 4 lists the individual measurements.
A total of 8 R = 48000 spectra were obtained with
FEROS between 2013 Mar 24 and 2013 May 13. De-
tails on the FEROS spectra as used by HATSouth have
been provided by Mohler-Fischer et al. (2013). For the
observations reported we did not follow the reduction
procedure described previously, and instead reduced the
data using an adapted version of the pipeline described
by Jord´an et al. (2014). This pipeline, which utilizes
cross-correlation against binary templates, was originally
developed for the CORALIE spectrograph on the Eu-
ler 1.2 m telescope at LSO. We found that applying this
pipeline to FEROS data yields a precision of ∼8 m s−1
for RV standard stars, which is significantly better than
the 20 m s−1
precision previously achieved for this in-
strument. This will be described in additional detail in
a separate paper (Brahm et al. in preparation).
The PFS observations consisted of an I2-free template
spectrum obtained on the night of UT 2013 Nov 8,
and 7 observations taken through an I2 cell obtained
between 2013 Nov 7 and 16. Observations were car-
ried out with a 0.′′
5 × 2.′′
5 slit, using 2 × 2 binning
and slow read-out mode. The spectra were reduced to
RVs in the bary-centric frame of the solar system fol-
lowing the method of Butler et al. (1996). We com-
puted bisector spans in a manner similar to that used
by Torres et al. (2007) to calculate bisector spans for
Keck/HIRES data. The presence of the I2 cell restricts
the spectral range over which the bisector spans may be
computed. Whereas in Torres et al. (2007), and previ-
ous studies using Keck/HIRES data, the bisector span
analysis was done on the bluest spectral orders which
are free of I2 absorption, the faintness and extreme red
color of HATS-6 makes the signal blueward of 5000 ˚A
too low to be used for a bisector analysis. We there-
fore use five orders covering the spectral range 6200 ˚A to
6540 ˚A. The limited spectral range reduces the precision
of the bisector spans. In fact we find that the bisector
spans calculated from the MPG 2.2 m/FEROS data have
lower scatter than those from Magellan/PFS. Nonethe-
less there is no significant trend in the bisector spans,
nor is there any evidence for more than one stellar com-
ponent in the Magellan/PFS cross-correlation functions.
We used our I2-free template spectrum from PFS
to measure Teff and [Fe/H] for HATS-6 following the
method of Neves et al. (2014). We made use of the
Python routines referenced in that paper to perform
this analysis, after modifying it for the spectral range of
PFS (we verified that the code reproduces the tempera-
ture and metallicity of the two HARPS spectra supplied
with the routines, when applied to the restricted spec-
tral range). We find Teff⋆ = 3770 ± 100 K and [Fe/H]=
0.200 ± 0.091, where the errors are determined from Ta-
ble 6 of Neves et al. (2014) scaling by Nall/Nused where
Nall is the number of spectral lines used by Neves et al.
(2014), and Nused is the number of lines within the PFS
spectral range.
The HARPS observations consisted of three exposures
taken on the nights of UT 2013 Dec 7–9. We used an
exposure time of 1200s on the first night and 1800 s on
the following two nights. Observations were carried out
in the “object+sky” mode (due to the faintness of the
target, contamination from scattered moonlight is sub-
stantial), and reduced to RVs using the facility Data Re-
duction Software (DRS) together with a K star spectral
mask (at present this is the coolest facility mask avail-
able). The spectra have a resolution of R = 115000 cov-
ering a range of 378 nm–691 nm.
In practice, due to the faintness of HATS-6 and the
low mass of the planet HATS-6b, the orbital variation is
detected with significance only from the PFS data. We
include the data from HARPS and FEROS in our RV
model (Section 3.2) for completeness, and to ensure that
the fit accounts for all data, including non-detections.
-200
-150
-100
-50
0
50
100
150
200
RV(ms-1
)
-250
-200
-150
-100
-50
0
50
100
O-C(ms-1
)
-1500
-1000
-500
0
500
1000
1500
0.0 0.2 0.4 0.6 0.8 1.0
BS(ms-1
)
Phase with respect to Tc
Fig. 4.— Top panel: High-precision RV measure-
ments for HATS-6 from Magellan/PFS (dark filled circles),
MPG 2.2 m/FEROS (open triangles), and ESO 3.6 m/HARPS
(stars), together with our best-fit circular orbit model. Zero phase
corresponds to the time of mid-transit. The center-of-mass veloc-
ity has been subtracted. The orbital fit is primarily constrained by
the PFS observations. Second panel: Velocity O−C residuals from
the best-fit model. The error bars for each instrument include the
jitter which is varied in the fit. Third panel: Bisector spans (BS),
with the mean value subtracted. Note the different vertical scales
of the panels.
3. ANALYSIS
3.1. Excluding blend scenarios
In order to rule out the possibility that HATS-6 is not
a planetary system, but is instead a blend between an
eclipsing binary star and another source, we carried out
a blend analysis similar to that done in Hartman et al.
(2012), with a difference being that in this case we use the
Dartmouth (Dotter et al. 2008) stellar evolution models
to calculate the properties of simulated blended systems.
We find that although there exist blend models involv-
ing a eclipsing binary blended with a brighter foreground
M dwarf which match the light curves and absolute pho-
7. HATS-6b 7
TABLE 3
Summary of spectroscopic observations
Telescope/Instrument Date Range Number of Observations Resolution Observing Mode
ANU 2.3 m/WiFeS 2012 May 13 1 3000 Recon Spectral Type
ANU 2.3 m/WiFeS 2012 Aug 6–Oct 24 4 7000 Recon RVs
du Pont 2.5 m/Echelle 2012 Oct 25–26 2 30000 Recon RVs/Spectral Type
Magellan Clay 6.5 m/PFS 2013 Nov 7–16 7 100000 High Precision RVs
MPG 2.2 m/FEROS 2013 Mar 24–May 11 8 48000 High Precision RVs
ESO 3.6 m/HARPS 2013 Dec 7–10 31 115000 High Precision RVs
TABLE 4
Relative radial velocities and bisector span measurements of
HATS-6.
BJD RVa σRV
b BS σBS Phase Instrument
(2 456 000+) (m s−1) (m s−1) (m s−1)
377.58801 30.48 32.00 115.0 14.0 0.961 FEROS
378.57524 −148.52 33.00 112.0 14.0 0.258 FEROS
401.48495 −4.52 33.00 182.0 14.0 0.147 FEROS
406.48479 −14.52 35.00 437.0 16.0 0.651 FEROS
424.46313 −176.52 69.00 −187.0 29.0 0.057 FEROS
603.77801c 21.86 7.09 · · · · · · 0.982 PFS
604.76307 −44.62 7.36 692.4 205.7 0.278 PFS
604.82373d · · · · · · −69.7 122.4 0.297 PFS
605.81892 49.82 5.79 −15.7 315.3 0.596 PFS
608.85541 −37.49 5.80 −296.4 243.2 0.509 PFS
609.79629 47.03 7.77 0.0 107.1 0.792 PFS
611.84038 −51.46 8.74 388.1 808.0 0.407 PFS
612.85205 81.60 8.84 −481.3 735.3 0.711 PFS
633.62669 −44.47 58.38 · · · · · · 0.958 HARPS
635.80096 18.01 59.69 · · · · · · 0.612 HARPS
636.79588 64.54 37.05 · · · · · · 0.912 HARPS
a The zero-point of these velocities is arbitrary. An overall offset γrel fitted sepa-
rately to the PFS, HARPS and FEROS velocities in Section 3 has been subtracted.
b Internal errors excluding the component of astrophysical/instrumental jitter
considered in Section 3.
c The CCF peak height was too low in the orders where we computed the BS to
be able to extract a BS measurement for this observation.
d This PFS observation was taken without the iodine cell to be used as a template.
The RV is not measured for this observations, but BS value is measured.
tometry, in all such cases both the foreground source and
the primary in the background binary have an appar-
ent magnitude difference |∆V | < 1 mag, so that cross-
correlation functions (CCFs) computed from the PFS,
FEROS and HARPS spectra would show obvious sec-
ondary peaks and RV variations greater than 1 km s−1
.
The simulated CCFs are grossly inconsistent with the ob-
served CCFs, so we conclude that this is not a blended
eclipsing binary system, and is instead a transiting planet
system.
As is often the case we cannot exclude the possibility
that HATS-6 is an unresolved binary system with one
component having a transiting planet. High resolution
imaging would provide constraints on any such wide bi-
nary companions. For the analysis presented here we
assume that this is an isolated star. If future observa-
tions reveal that this is a binary system, corrections to
the planet mass and radius would increase their values
from those presented in this paper.
3.2. Global Fit of Light Curves and RV Measurements
In order to determine the physical parameters of the
HATS-6 system we carried out an analysis similar to that
described in Bakos et al. (2010); Penev et al. (2013).
All light curves (HATSouth data and follow-up data)
and RV measurements are simultaneously fitted using
a Mandel & Agol (2002) transit light curve model and a
Keplerian RV orbit.
The light curve model is extended using a model for
instrumental variations such that the total model can be
expressed as:
mk,i = mk,0 + ∆m(ti; T0, TNt , ζ/R⋆, Rp/R⋆, b, aLD,k, bLD,k)
+
NEPD,k
j=1
cEPD,k,jxk,j,i +
NTFA
j=1
cTFA,jyk,j,i (1)
where mk,i is the measured magnitude to be modeled
for observation i of light curve k; mk,0 is the zero-point
magnitude for light curve k (which is a free parameter in
the model); ∆m(ti; T0, TNt , ζ/R⋆, Rp/R⋆, b, aLD,k, bLD,k)
is the physical Mandel & Agol (2002) model evaluated
at time ti and parameterized by initial and final tran-
sit epochs T0 and TNt (the period is then given by
(TNt − T0)/Nt), reciprocal of the half duration of the
transit ζ/R⋆, ratio of the planetary and stellar radii
Rp/R⋆, normalized impact parameter b, and quadratic
limb darkening coefficients aLD,k and bLD,k appropriate
8. 8 Hartman et al.
for the filter of light curve k (except for aLD,k and bLD,k,
which are fixed using the tabulations of Claret (2004),
these parameters are varied in the fit); there are NEPD,k
EPD parameters applied to light curve k with cEPD,k,j
being the free coefficient fitted for EPD parameter series
j applied to light curve k, and xk,j,i being the value of
EPD parameter series j at observation i for light curve
k; and there are NTFA TFA templates used to fit the
light curve, with cTFA,j being the free coefficient fitted
for template j and yk,j,i being the value of template j
at observation i for light curve k. For the HATSouth
light curve we do not include the EPD and TFA terms
in the fit, and instead model the light curve that was
pre-processed through these filtering routines without ac-
counting for the transits. In this case we also include
an instrumental blending factor (varied in the fit) which
scales the depth of the Mandel & Agol (2002) model ap-
plied to the HATSouth light curve by a factor between
0 and 1 (assuming a uniform prior between these limits)
to account for both blending from nearby stars as well
as the artificial dilution of signals due to the filtering.
For the RV model we allow an independent RV zero-
point, and an independent RV jitter for each of the three
instruments used. The jitter is a term added in quadra-
ture to the formal RV uncertainties for each instrument
and is varied in the fit following Hartman et al. (2012).
We use a Differential Evolution Markov-Chain
Monte Carlo (DEMCMC) procedure (ter Braak 2006;
Eastman et al. 2013) to explore the fitness of the model
over parameter space and produce a chain of parameters
drawn from the posterior distribution. This chain is then
used to estimate the most likely value (taken as the me-
dian value over the chain) together with the 68.3% (1σ)
confidence interval for each of the physical parameters.
The fit is performed both allowing the eccentricity to
vary, and fixing it to zero. We find that without ad-
ditional constraints, the free-eccentricity model strongly
prefers a non-zero eccentricity of e = 0.404 ± 0.058. This
is entirely due to the PFS velocities which closely fol-
low such an eccentric orbit with a near-zero jitter for the
PFS RVs of 0.1±5.6 m s−1
. When the eccentricity is fixed
to zero, on the other hand, the PFS RVs are consistent
with a circular orbit, but in this case require a jitter of
26±14m s−1
. Due to the faintness of HATS-6 in the opti-
cal band-pass, and consequent sky contamination, such a
high “jitter” is not unreasonable, and may simply reflect
an underestimation of the formal RV uncertainties. As
we discuss below, the stellar parameters inferred for the
high eccentricity solution are inconsistent with the spec-
troscopic parameters and broad-band photometric colors
of the star. When the photometric observations are di-
rectly folded into our light curve and RV modelling, as
we discuss in Section 3.3.2, the preferred eccentricity is
consistent with zero (e = 0.053 ± 0.060).
3.3. Determining the Physical Parameters of the Star
and Planet
To determine the mass and radius of the transiting
planet from the physical parameters measured above re-
quires knowledge of the stellar mass and radius. For
a non-binary star such as HATS-6 these parameters are
not easy to measure directly and instead must be inferred
by comparing other measurable parameters, such as the
surface temperature and bulk stellar density, with theo-
retical stellar evolution models (requiring the metallicity,
a color indicator, and a luminosity indicator to identify
a unique stellar model), or with empirical relations cali-
brated using binary stars. We considered both methods,
discussed in turn below.
3.3.1. Dartmouth Models
Because the star is a cool dwarf we make use of
the Dartmouth stellar evolution models (Dotter et al.
2008) which appear to provide the best match to M
dwarf and late K dwarf stars (e.g. Feiden et al. 2011;
Sandquist et al. 2013). We also use the effective tem-
perature and metallicity measured from the PFS I2-free
template spectrum.
We use the results from our DEMCMC analysis of the
light curve and radial velocity data (Section 3.2) together
with the Dartmouth isochrones to determine the stel-
lar parameters. For each density measurement in the
posterior parameter chain we associate Teff and [Fe/H]
measurements drawn from Gaussian distributions. We
look up a matching stellar model from the Dartmouth
isochrones, interpolating between the tabulated models,
and append the set of stellar parameters associated with
this model to the corresponding link in the posterior pa-
rameter chain. Other planetary parameters, such as the
mass and radius, which depend on the stellar parameters
are then calculated for each link in the chain.
Figure 5 compares the measured Teff and ρ⋆ values
for HATS-6 to the interpolated [Fe/H]= 0.20 Dartmouth
isochrones. We also compare the V − K and ρ⋆ values
to these same isochrones. For reference we show seven
transiting-planet-hosting stars with Teff⋆, V − K, ρ⋆ and
M⋆ similar to that of HATS-6. These are listed as well
in Table 8. At fixed Teff or V − K the models predict
ρ⋆ values that are slightly lower than those seen amongst
the transit hosts. This suggests that using V − K as an
input in constraining the mass of the star through the
Dartmouth models may lead to a slightly overestimated
stellar mass (lower densities yield higher masses). For
comparison we also show the relations derived from the
empirical relations discussed below. The empirical rela-
tions appear to provide a better match to the stars shown
in Figure 5.
As noted in Section 3.2 when we allow the eccentricity
to vary in the fit the PFS data pull the model toward
a high eccentricity solution (e = 0.404 ± 0.058) which
also yields a high stellar density of 14.8 ± 2.9 g cm−3
.
The combination of the high stellar density, hot effective
temperature (Teff⋆ = 3770 ± 100 K) and high metallic-
ity ([Fe/H]= 0.200 ± 0.091) cannot be matched by the
Dartmouth isochrones. If we instead use V − K as the
temperature indicator and draw metallicities from the
Haywood (2001) solar neighborhood metallicity distri-
bution we find that only very low metallicity models
([Fe/H] = −0.63±0.07) match the observations. Such a
metallicity is at odds with the spectroscopic measure-
ment. Moreover, taking the parameters from the ec-
centric model, and assuming QP = 106
the circular-
ization timescale (e.g. Adams & Laughlin 2006) is only
342 ± 35 Myr. No planets with tcirc < 1 Gyr have been
found with eccentricities greater than 0.1 (e.g. see Fig. 12
of Bakos et al. 2012), making it unlikely that HATS-6b
has such a high eccentricity.
9. HATS-6b 9
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
340036003800400042004400
ρ*[g/cm
3
]
Effective temperature [K]
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
3 3.2 3.4 3.6 3.8 4 4.2 4.4
ρ*[g/cm
3
]
V-K [mag]
0.50
0.52
0.54
0.56
0.58
0.60
0.62
0.64
0.66
0.68
0.70
3 3.2 3.4 3.6 3.8 4 4.2 4.4
M*[Msun]
V-K [mag]
Fig. 5.— Model isochrones (dashed lines) from Dotter et al.
(2008) for the spectroscopically determined metallicity of HATS-6
and ages of 1 to 13 Gyr in 1 Gyr steps (showing ρ⋆ vs Teff at top,
ρ⋆ vs V − K in the middle, and M⋆ vs V − K at the bottom). The
measured values of Teff , V −K, and ρ⋆ for HATS-6, and the value of
M⋆ inferred from comparison to the stellar models, are shown using
the large filled circles together with their 1σ and 2σ confidence
ellipsoids. The open triangles show other transiting planet host
stars with measured Teff , V − K, ρ⋆ and M⋆ values similar to
HATS-6. Near the K/M spectral type boundary (V − K ∼ 4) the
models predict somewhat lower densities for a given V − K or Teff
than are seen among transit hosts (Table 8). For comparison we
also show the relations derived from our empirical model (dotted
lines; Section 3.3.2). In the top panel we show the three dotted lines
are the median relation, and the 1σ lower and upper bounds. In
the bottom two panels the lower dotted line is the median relation,
while the upper dotted line is the 1σ upper bound. The 1σ lower
bound from the empirical model lies just outside the range of these
plots (below the bottom left corner in each case). The empirical
models appear to be more consistent with the transiting planet
hosts than the theoretical models, but also cover a broader range
of parameter space than seen among the transit hosts.
3.3.2. Empirical Relations
As an alternative method to determine the stellar pa-
rameters, and to better understand the degree of sys-
tematic errors in these parameters, we also develop a
set of empirical relations between stellar density, which
is directly measured for a transiting planet system, and
other stellar parameters. Such relations have been devel-
oped and employed in transiting exoplanet studies previ-
ously (Torres et al. 2010; Enoch et al. 2010; Southworth
2011). The Torres et al. (2010) and Enoch et al. (2010)
relations only considered stars with M > 0.6 M⊙, making
them inapplicable in this case. The Southworth (2011)
relations consider stars over the range 0.2 M⊙ < M <
3.0 M⊙. They present two relations, one for mass as
a function of temperature, density and metallicity, the
other for radius as a function of temperature, density
and metallicity. Fitting these as two independent func-
tions ignores the fact that density, mass, and radius must
satisfy the relation M = 4
3 πR3
ρ. Moreover, one should
not expect the scaling of mass and radius with metal-
licity or temperature to be independent of stellar mass
over such a broad range in mass. And, since metallicity
is available for only very few M dwarf eclipsing binaries,
the fit performed by Southworth (2011) effectively im-
poses the metallicity scaling for A through G stars on
the M dwarfs. We therefore consider it worthwhile to
revisit these relations for K and M dwarf stars.
Johnson et al. (2011) and Johnson et al. (2012) have
also developed empirical relations for characterizing M
dwarf planet hosts, applying them to the characteriza-
tion of LHS 6343 AB and Kepler-45, respectively. Our
approach is similar to theirs in that we make use of re-
lations between mass and absolute magnitudes based on
data from Delfosse et al. (2000), and we also consider the
empirical mass–radius relation based on eclipsing bina-
ries, however we differ in the sample of eclipsing binaries
that we consider, and we adopt a different parameter-
ization of the problem. Moreover, while Johnson et al.
(2012) use several empirical relations which were inde-
pendently fit using different data sets, our approach is
to self-consistently determine all of the relations through
a joint analysis of the available data. We discuss this
comparison in more detail below.
We look for the following relations: (1) ρ⋆ → R⋆ (which
also defines a ρ⋆ → M⋆ relation), (2) M⋆ → Mbol, (which
together with relation 1 also defines a relation between
Teff⋆ and the other parameters) (3) Teff⋆ → Mbol − MV ,
(4) Teff⋆ → Mbol − MJ , (5) Teff⋆ → Mbol − MH, (6)
Teff⋆ → Mbol − MK. The motivation for choosing this
particular formulation is that ρ⋆ is typically a well-
measured parameter for transiting planet systems, and
the relation between ρ⋆ and R⋆ is tighter than for other
relations involving ρ⋆. The other relations are then
based on physical dependencies (bolometric magnitude
depends primarily on stellar mass, with age and metal-
licity being secondary factors, and bolometric corrections
depend primarily on effective temperature, with metal-
licity being a secondary factor). These relations are pa-
rameterized as follows:
10. 10 Hartman et al.
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
2 5 10 20 50
RStar/RSun
ρStar [g cm
-3
]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
2 5 10 20 50
(∆RStar)/RStar
ρStar [g cm
-3
]
0.2
0.3
0.4
0.5
0.6
0.7
0.8
2 5 10 20 50
MStar/MSun
ρStar [g cm
-3
]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
2 5 10 20 50
∆MStar/MStar
ρStar [g cm
-3
]
3
4
5
6
7
8
9
10
11
12
13
0.2 0.3 0.4 0.5 0.6 0.7 0.80.9
Mbol[mag]
MStar/MSun
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0.2 0.3 0.4 0.5 0.6 0.7 0.80.9
∆Mbol[mag]
MStar/MSun
Fig. 6.— Top: Empirical relation between stellar density and radius (equation 2, with parameters given in Table 7). The solid line
shows the best-fit relation with dR = 0, the dashed lines show the expected 1σ spread for this relation allowing dR to be drawn from a
Gaussian distribution with standard deviation SR. The points show the eclipsing binary components from Table 5 used to fit this relation.
Middle: Same as top, here we show the empirical relation between stellar density and mass. Bottom: Same as top, here we show the
empirical relation between stellar mass and bolometric magnitude. On the right-hand panels we show the fractional residuals from the
best-fit models, the short-dashed (blue) lines show the expected relations from the Dartmouth stellar models for an age of 4.5 Gyr and
solar metallicity, while the longer dashed (red) lines show the expected 1σ spread from the empirical model. The solar-metallicity 4.5 Gyr
Dartmouth models predict systematically larger radii at fixed density, and brighter bolometric magnitudes at fixed mass, than observed in
the eclipsing binary sample. The empirical models provide a good fit to these data, by design.
lR =
aρ,0
aρ,1
aρ,2
aρ,3
T
0.131674 −0.605624 0.739127 −0.263765
−0.494952 0.614479 0.437886 −0.430922
−0.765425 −0.291096 0.099548 0.565224
0.389626 0.413398 0.502032 0.652117
1
lρ
lρ2
lρ3
+ dlR (2)
Mbol =
bm,0
bm,1
bm,2
bm,3
T
−0.042114 −0.349391 −0.787638 −0.505746
0.170316 0.723492 0.095153 −0.662192
−0.309788 −0.505183 0.591641 −0.546610
−0.934479 0.315080 −0.143296 0.083309
1
lM
lM2
lM3
+ dMbol (3)
11. HATS-6b 11
-2
-1
0
1
2
3
4
5
6
7
2000 2500 3000 3500 4000 4500 5000 5500
MV-Mbol[mag]
Τeff [K]
-3
-2.5
-2
-1.5
-1
-0.5
0
2000 2500 3000 3500 4000 4500 5000 5500
MJ-Mbol[mag]
Τeff [K]
-3.4
-3.2
-3
-2.8
-2.6
-2.4
-2.2
-2
-1.8
-1.6
-1.4
2000 2500 3000 3500 4000 4500 5000 5500
MH-Mbol[mag]
Τeff [K]
-4
-3.5
-3
-2.5
-2
-1.5
2000 2500 3000 3500 4000 4500 5000 5500
MK-Mbol[mag]
Τeff [K]
Fig. 7.— Top: Empirical relation between effective temperature and the bolometric correction in V -band (upper left), J-band (upper
right), H-band (lower left) and K-band (lower right). In each case the solid line is the median relation, while the dashed lines show the
1σ confidence region about the median relation. The points in this plot correspond to stars in Table 6 with Teff and Mbol for each star
determined as part of the empirical model fitting procedure. Because Teff and Mbol are not directly observed parameters for these stars,
but are rather determined through the modelling, and largely constrained by the stellar mass, which is observed, the data appear to follow
the model very closely. This should not be taken as validation of the model (see instead Figure 8), rather the purpose of showing these
plots is to demonstrate the form of the bolometric correction, its uncertainty, as well as the range of temperatures over which the model is
constrained.
BCλ =
cλ,0
cλ,1
cλ,2
T
0.871464 −0.485768 0.067675
0.484681 0.831841 −0.270418
0.075065 0.268461 0.960361
1
lT
lT 2
(4)
where lR = log10(R), lρ = log10(ρ), lM = log10(M),
lT = log10(Teff) are the logarithms of the stellar radius
in solar units, density in cgs units, mass in solar units
and temperature in Kelvin, respectively. The sets of co-
efficients in the vectors to the left of the matrices (e.g.,
aρ,0, aρ,1, etc.; optimal values are given in Table 7) are
varied in the fit, and the matrices are chosen to minimize
correlations between these parameters. The matrices are
determined by initially fitting the relations using simple
polynomials (i.e. we replace the matrices in the relations
above with the identity matrix), and then performing a
Principal Component Analysis on the resulting Markov
Chains to determine the transformation to a linearly un-
correlated set of parameters. These matrices are held
fixed in a subsequent fit where we determine the opti-
mized values of the parameters aρ,0, aρ,1, etc. (see below
for more discussion of the fitting procedure). The term
λ is either V , J, H or K. To allow for intrinsic scatter in
the relations, the terms dlR and dMbol represent real de-
viations in the radius or bolometric magnitude from the
model. Such deviations are expected due to additional
parameters, such as the metallicity or age, which are not
included in this model. Every star has its own value of
dlR and dMbol, assumed to be drawn from Gaussian dis-
tributions with standard deviations of SR and SMbol, re-
spectively. The following auxiliary relations are also used
to relate the stellar density to the mass, the bolometric
magnitude and radius to the effective temperature, and
the bolometric magnitude and bolometric correction to
the absolute magnitude in a given filter (Mλ):
lM = lρ − 0.14968 + 3lR(lρ) (5)
lT = (42.227 − 5lR − Mbol)/10 (6)
Mλ = Mbol + BCλ. (7)
The stars that we use in the fit are listed in Tables 5
and 6. The eclipsing binaries are compiled from tables in
Zhou et al. (2014), Torres et al. (2010), and Nefs et al.
(2013), and include non-pre-main-sequence stars with
M⋆ < 0.85 M⊙ and with M⋆ and R⋆ measured to better
than 5% accuracy. The upper mass limit corresponds
roughly to the mass for which stars older than the pre-
12. 12 Hartman et al.
0
2
4
6
8
10
12
14
16
18
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
MV[mag]
Mass [Msun]
3
4
5
6
7
8
9
10
11
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
MJ[mag]
Mass [Msun]
1
2
3
4
5
6
7
8
9
10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
MH[mag]
Mass [Msun]
1
2
3
4
5
6
7
8
9
10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
MK[mag]
Mass [Msun]
Fig. 8.— Top: Same as Figure 7, here we show the empirical relation between stellar mass and the absolute magnitudes in the V , J, H
and K bands. The residuals from these fits are shown in Figure 9.
main-sequence phase, and with −0.5 < [Fe/H] < 0.5,
will have log g > 4.4 throughout the ∼ 10 Gyr age of
the Galactic disk. Stars below this mass show tight cor-
relations between the density and the mass, radius and
luminosity. Because individual broad-band photometric
magnitudes are not available for most of the eclipsing
binary components, we use resolved binaries for which
masses and component magnitudes are available to con-
strain relations (3) through (6) above. Most of these
stars are taken from the compilation by Delfosse et al.
(2000), with a few objects from the list of Torres et al.
(2010) to extend into the late K dwarf regime.
To fit the above relations we use a likelihood function
of the form:
ln L = −
1
2
N⋆
i=1
lR(lρi) − lRobs,i
σlR,i
2
(8)
−
1
2
N⋆
i=1
lM(lρi) − lMobs,i
σlM,i
2
−
1
2
N⋆
i=1
lT (lR(lρi), Mbol(lM(lρi))) − lTobs,i
σlT,i
2
−
1
2
λ
N⋆
i=1
Mbol(lM(lρi)) + BCλ(lT (lR(lρi), Mbol(lM(lρi)))) − Mλ,obs,i
σλ,i
2
−
1
2
N⋆
i=1
ln(S2
R) +
dlRi
SR
2
−
1
2
N⋆
i=1
ln(S2
Mbol) +
dMbol,i
SMbol
2
where the sum on λ is over the four filters V , J, H and K, and for each star we exclude terms from the sums if
13. HATS-6b 13
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
∆MV[mag]
Mass [Msun]
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
∆MJ[mag]
Mass [Msun]
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
∆MH[mag]
Mass [Msun]
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
∆MK[mag]
Mass [Msun]
Fig. 9.— Same as Figure 8, here we show residuals from the median empirical relation. The short-dash (blue) lines show the relation
from the 4.5 Gyr, Solar metallicity Dartmouth models, while the long-dash (red) lines show the expected 1σ spread of the empirical model.
the relevant measurement (lRobs, lMobs, lTobs, MV,obs,
MJ,obs, MH,obs, or MK,obs) is not available. Here lρi,
dlRi, and dMbol,i are free parameters for each star i, and
the other free parameters are SR, SMbol, and the coeffi-
cients in equations 2–4. We use the DEMCMC procedure
to explore this likelihood function. Table 7 provides the
values for the best-fit model together with their approx-
imate 1σ (uncorrelated) uncertainties.14
Figure 6 shows the fit between lρ, lM and lR, and
between lM and Mbol, together with the residuals from
this model, Figure 7 shows the relations between effec-
tive temperature and the V , J, H, and K bolometric
corrections, Figure 8 shows the relation between mass
and the absolute magnitudes in each of these filters, and
Figure 9 shows the residuals from the fits in Figure 8.
Our model yields intrinsic scatters of ∼ 2% in radius and
∼ 7% in mass, and 4% to 10% in effective temperature
(between 0.2 mag and 0.5 mag in bolometric magnitudes)
given a value for ρ⋆. Figure 10 compares the precision
in the inferred mass and radius implied by this modeling
when using a single parameter to constrain the stellar
properties (either ρ⋆, MV , MK or V − K), and when
using various combinations of observables. Assuming no
observational uncertainties, MK is the highest precision
stellar mass indicator, while ρ⋆ is the highest precision
stellar radius indicator. By combining ρ⋆ with a photo-
14 A C code implementing these relations to de-
termine the properties of K and M dwarf stars
from various observed quantities is available at
http://www.astro.princeton.edu/~jhartman/kmdwarfparam.html.
metric indicator, such as MK, it is possible to improve
the precision in mass and radius by up to a factor of two
compared to the precision allowed by using only ρ⋆.
Note that due to the somewhat higher scatter in the
stellar parameters at the high mass end, and the small
number of stars constraining the fit at this end, we find
that the stellar mass as a function of density reaches
a local maximum of ∼ 0.8 M⊙ at ρ ∼ 1.5 g cm−3
. We
therefore do not suggest using these models for stars with
M > 0.8 M⊙, or spectral types earlier than K5.
It is worth comparing our modeling to that done
by Johnson et al. (2011) and Johnson et al. (2012).
One significant difference is the treatment of metallic-
ity. Johnson et al. (2011) include a correlation between
metallicity and ∆MK (Johnson & Apps 2009), while
Johnson et al. (2012) include an additional correlation
between metallicity and ∆J − K in their modelling. We
choose not to include metallicity explicitly in our model
due to the lack of a large sample of M dwarfs with well-
measured masses, radii and metallicities. Lacking such
a dataset, it is not possible to determine the effect of
metallicity on all of the relations considered. Instead
the metallicity is assumed to contribute to the intrin-
sic uncertainty in the ρ → R and M → Mbol relations,
measured using the SR and SMbol parameters. While,
like us, Johnson et al. (2011) use eclipsing binaries in
calibrating the mass–radius relation, their sample is the
Ribas (2006) catalog which contained only 14 stars with
M < 0.8 M⊙, of which only 10 had masses and radii mea-
sured to better than 5% precision. Johnson et al. (2012),
on the other hand, choose to use stars with interferomet-
14. 14 Hartman et al.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
FractionalPrecision
Mass [Msun]
ρ
MV
MK
V-K
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
FractionalPrecision
Radius [Rsun]
ρ
MV
MK
V-K
0.02
0.025
0.03
0.035
0.04
0.045
0.05
0.055
0.06
0.065
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
FractionalPrecision
Mass [Msun]
ρ + MK
ρ + V-K
V-K + MK
ρ + V-K + MK
0.01
0.015
0.02
0.025
0.03
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
FractionalPrecision
Radius [Rsun]
ρ + MK
ρ + V-K
V-K + MK
ρ + V-K + MK
Fig. 10.— Top: Comparison of the precision with which stellar mass (left) and stellar radius (right) may be measured using either ρ⋆,
MV , MK, or V − K as an observed parameter. For each observable we step through a range of values determining the median stellar mass
(radius) and its standard deviation using the empirical relations given in equations 2 through 4. We find that MK is the highest precision
stellar mass indicator, allowing a precision that varies between ∼ 3% and 6%, whereas ρ⋆ is the highest precision stellar radius indicator,
allowing a precision of ∼ 2% over the range 0.2 R⊙ < R < 0.9 R⊙. Bottom: Comparison of the precision with which stellar mass (left)
and stellar radius (right) may be measured using the combinations of parameters indicated in the figure. Combining the density with an
absolute magnitude indicator allows for a mass precision between 2.5% and 4.5%, and a radius precision between ∼ 1% and ∼ 2%.
rically measured radii from Boyajian et al. (2012) due
to the possibility that the eclipsing binaries are system-
atically inflated compared to single stars. While these
stars have directly measured radii, their masses must
be estimated using an assumed mass–luminosity rela-
tion. The few long period, low-mass eclipsing binaries
which have been studied have parameters that are con-
sistent with the shorter period binaries (Irwin et al. 2011;
Doyle et al. 2011), moreover Boyajian et al. (2012) find
no systematic difference between the mass–radius rela-
tion determined from their single stars (for an assumed
mass–luminosity relation), and the mass–radius relation
determined from short period eclipsing binaries, so we
choose to use the eclipsing binaries for which both masses
and radii are measured directly.
Having established our empirical stellar model, we use
it to determine the properties of HATS-6 by incorpo-
rating it directly into our light curve and RV curve fit.
To do this we add the following terms to our likelihood
function:
−
1
2
λ
Mλ(lρ, dlR, dMbol) + ∆d + Aλ − mλ
σλ
2
−
1
2
dlR
SR
2
+
dMbol
SM
2
(9)
Where Mλ is the predicted absolute magnitude in filter
λ given dlR, dMbol, and lρ, which is determined from
the other free parameters in the model (b2
, ζ/R⋆, P,√
e sin ω,
√
e cos ω, and K); ∆d is the distance modulus
and Aλ is the extinction; mλ is the observed magnitude;
and σλ is the magnitude uncertainty. The sum is over
the filters λ = V , J, H, and K. The new parameters
introduced in the fit are thus dlR, dMbol, ∆d and AV .
We restrict AV to be in the range [0, 0.175] where the
upper limit is the total line-of-sight extinction from the
Schlafly & Finkbeiner (2011) reddenning maps, and we
assume the Cardelli et al. (1989) extinction law to relate
AV to the extinction in the other band-passes. Given
lρ, dlR, and dMbol at each link in the resulting Markov
Chain, we then calculate all relevant stellar parameters,
and dependent planetary parameters.
Using the empirical model we find M⋆ =
0.574+0.020
−0.027 M⊙ and R⋆ = 0.570 ± 0.011 R⊙, as-
suming a circular orbit, and M⋆ = 0.573 ± 0.031 M⊙
and R⋆ = 0.567 ± 0.037 R⊙, allowing for an eccentric
orbit. The mass and radius inferred assuming a circular
orbit are slightly lower than, though consistent with,
the parameters inferred using the Dartmouth isochrones
(M⋆ = 0.595 ± 0.017M⊙, and R⋆ = 0.5759 ± 0.0092R⊙).
The precision allowed by both the Dartmouth and
empirical models are similar. When we allow the eccen-
tricity to vary with our empirical model the constraint
from the observed V −K color of the star pulls the model
15. HATS-6b 15
TABLE 5
K and M Dwarf Binary Components Used to Fit Empirical Relations a
Star Mass Radius Teff Reference
(M⊙) (R⊙) (K)
1 RXS J154727.5+450803 A 0.2576 ± 0.0085 0.2895 ± 0.0068 . . . 1
1 RXS J154727.5+450803 B 0.2585 ± 0.0080 0.2895 ± 0.0068 . . . 1
ASA J011328–3821.1 A 0.612 ± 0.03 0.596 ± 0.02 3750 ± 250 2
CG Cyg B 0.814 ± 0.013 0.838 ± 0.011 4720 ± 60 3,4
CM Dra A 0.2130 ± 0.0009 0.2534 ± 0.0019 3130 ± 70 5
CM Dra B 0.2141 ± 0.0010 0.2396 ± 0.0015 3120 ± 70 5
CU Cnc A 0.4333 ± 0.0017 0.4317 ± 0.0052 3160 ± 150 6
CU Cnc B 0.3980 ± 0.0014 0.3908 ± 0.0094 3130 ± 150 6
GJ 3236 A 0.376 ± 0.016 0.3795 ± 0.0084 3310 ± 110 7
GJ 551 b 0.123 ± 0.006 0.141 ± 0.007 3098 ± 56 8,9,10
GU Boo A 0.610 ± 0.006 0.627 ± 0.016 3920 ± 130 11
GU Boo B 0.600 ± 0.006 0.624 ± 0.016 3810 ± 130 11
HATS550-016 0.110+0.005
−0.006 0.147+0.003
−0.004 . . . 12
HATS551-021 0.132+0.014
−0.005 0.154+0.006
−0.008 . . . 12
HD 195987 A 0.844 ± 0.018 0.98 ± 0.04 5200 ± 100 13
J1219-39 B 0.091 ± 0.002 0.1174+0.0071
−0.0050 . . . 14
Kepler-16 B 0.20255+0.00066
−0.00065 0.22623+0.00059
−0.00055 . . . 15
KIC 1571511 B 0.14136+0.0051
−0.0042 0.17831+0.0013
−0.0016 . . . 16
KOI-126 B 0.2413 ± 0.0030 0.2543 ± 0.0014 . . . 17
KOI-126 C 0.2127 ± 0.0026 0.2318 ± 0.0013 . . . 17
LSPM J1112+7626 A 0.3946 ± 0.0023 0.3860 ± 0.0055 3060 ± 160 18
LSPM J1112+7626 B 0.2745 ± 0.0012 0.2978 ± 0.0049 2950 ± 160 18
MG1-116309 A 0.567 ± 0.002 0.552 ± 0.0085 3920 ± 80 19
MG1-116309 B 0.532 ± 0.002 0.532 ± 0.006 3810 ± 80 19
MG1-1819499 A 0.557 ± 0.001 0.569 ± 0.0022 3690 ± 80 19
MG1-1819499 B 0.535 ± 0.001 0.500 ± 0.0085 3610 ± 80 19
MG1-2056316 A 0.4690 ± 0.0021 0.441 ± 0.002 3460 ± 180 19
MG1-2056316 B 0.382 ± 0.001 0.374 ± 0.002 3320 ± 180 19
MG1-506664 A 0.584 ± 0.002 0.560 ± 0.0025 3730 ± 90 19
MG1-506664 B 0.544 ± 0.002 0.513 ± 0.0055 3610 ± 90 19
MG1 646680A 0.499 ± 0.002 0.457 ± 0.006 3730 ± 50 19
MG1-646680 B 0.443 ± 0.002 0.427 ± 0.006 3630 ± 50 19
MG1-78457 B 0.491 ± 0.002 0.471 ± 0.009 3270 ± 100 19
NSVS 01031772 A 0.5428 ± 0.0027 0.526 ± 0.0028 3615 ± 72 20
NSVS 01031772 B 0.4982 ± 0.0025 0.5087 ± 0.0031 3520 ± 30 20
NSVS 6550671 A 0.510 ± 0.02 0.550 ± 0.01 3730 ± 60 21
T-Cyg1-01385 B 0.43 ± 0.02 0.40 ± 0.02 . . . 22
UV Psc B 0.7644 ± 0.0045 0.835 ± 0.018 4750 ± 80 23
V568 Lyr B 0.8273 ± 0.0042 0.7679 ± 0.0064 4900 ± 100 24
WOCS 23009 B 0.447 ± 0.011 0.4292 ± 0.0033 3620 ± 150 25
WTS19b-2-01387 A 0.498 ± 0.019 0.496 ± 0.013 3498 ± 100 26
WTS19b-2-01387 B 0.481 ± 0.017 0.479 ± 0.013 3436 ± 100 26
YY Gem A 0.599 ± 0.005 0.619 ± 0.006 3819 ± 98 27
YY Gem B 0.599 ± 0.005 0.619 ± 0.006 3819 ± 98 27
References. — 1: Hartman et al. (2011); 2: Helminiak et al. (2012); 3: Bedford et al. (1987); 4:
Popper (1994); 5: Morales et al. (2009); 6: Ribas (2003); 7: Irwin et al. (2009); 8: S´egransan et al.
(2003); 9: Valenti & Fischer (2005); 10: Demory et al. (2009); 11: L´opez-Morales & Ribas (2005);
12: Zhou et al. (2014); 13: Torres et al. (2002); 14: Triaud et al. (2013a); 15: Doyle et al. (2011);
16: Ofir et al. (2012); 17: Carter et al. (2011); 18: Irwin et al. (2011); 19: Kraus et al. (2011); 20:
Lopez-Morales et al. (2006); 21: Dimitrov & Kjurkchieva (2010); 22: Fernandez et al. (2009); 23:
Popper (1997); 24: Grundahl et al. (2008); 25: Sandquist et al. (2013); 26: Birkby et al. (2012);
27: Torres & Ribas (2002)
a Data compiled primarily from tables given in Torres et al. (2010), Nefs et al. (2013) and
Zhou et al. (2014), we provide the original references for each source in the table.
b This is a single star, with an interferometric radius measurement, and mass estimated assuming
a mass-luminosity relation.
to a lower eccentricity solution, yielding parameters that
are consistent with those from the fixed-circular model.
For the final parameters we suggest adopting those from
the empirical stellar model, assuming a circular orbit.
The adopted stellar parameters are listed in Table 9
while the planetary parameters are listed in Table 10.
4. DISCUSSION
In this paper we have presented the discovery of the
HATS-6 transiting planet system by the HATSouth sur-
vey. We found that HATS-6b has a mass of 0.319 ±
0.070 MJ, radius of 0.998 ± 0.019 RJ and orbits a star
with a mass of 0.574+0.020
−0.027 M⊙. HATS-6 is one of only
four stars with M 0.6 M⊙ known to host a short period
gas giant planet (the other three are WASP-80, WASP-
43, and Kepler-45; see Table 8). This is illustrated in
Figure 11 where we plot planet mass against the host
star mass. We note that the published masses for these
stars come from a disparate set of methods. Apply-
ing the empirical relations developed in this paper (Sec-
tion 3.3.2) to these two systems, using ρ⋆, V , J, H and
16. 16 Hartman et al.
TABLE 6
K and M Dwarf Stars with Absolute Magnitudes and Measured Masses Used in
Fitting the Bolometric Corrections in the Empirical Stellar Model a
Star Mass MV MJ MH MK
(M⊙) (mag) (mag) (mag) (mag)
Gl 866 C 0.0930 ± 0.0008 17.43 ± 0.40 . . . . . . . . .
Gl 65 B 0.100 ± 0.010 15.87 ± 0.06 10.06 ± 0.05 9.45 ± 0.03 9.16 ± 0.07
Gl 65 A 0.102 ± 0.010 15.41 ± 0.05 9.68 ± 0.05 9.15 ± 0.03 8.76 ± 0.07
Gl 234 B 0.1034 ± 0.0035 16.16 ± 0.07 10.31 ± 0.25 9.56 ± 0.10 9.26 ± 0.04
Gl 623 B 0.1142 ± 0.0083 16.02 ± 0.11 10.47 ± 0.29 9.35 ± 0.05 9.33 ± 0.14
Gl 866 B 0.1145 ± 0.0012 15.64 ± 0.08 . . . 9.29 ± 0.04 8.96 ± 0.04
Gl 866 A 0.1187 ± 0.0011 15.39 ± 0.07 . . . . . . . . .
Gl 791.2 B 0.126 ± 0.003 16.64 ± 0.10 . . . . . . . . .
Gl 473 B 0.131 ± 0.010 15.00 ± 0.07 9.57 ± 0.06 9.04 ± 0.07 8.84 ± 0.08
Gl 473 A 0.143 ± 0.011 15.01 ± 0.07 9.44 ± 0.06 8.84 ± 0.06 8.40 ± 0.06
Gl 831 B 0.1621 ± 0.0065 14.62 ± 0.08 . . . 8.62 ± 0.05 8.36 ± 0.05
Gl 860 B 0.1762 ± 0.0066 13.46 ± 0.09 9.03 ± 0.08 8.40 ± 0.05 8.32 ± 0.07
Gl 747 B 0.1997 ± 0.0008 12.52 ± 0.06 . . . . . . 7.63 ± 0.04
Gl 234 A 0.2027 ± 0.0106 13.07 ± 0.05 8.52 ± 0.06 7.93 ± 0.04 7.64 ± 0.04
CMDra B 0.2136 ± 0.0010 12.94 ± 0.10 . . . . . . . . .
Gl 747 A 0.2137 ± 0.0009 12.30 ± 0.06 . . . . . . 7.53 ± 0.04
CMDra A 0.2307 ± 0.0010 12.80 ± 0.10 . . . . . . . . .
Gl 860 A 0.2711 ± 0.0100 11.76 ± 0.05 7.84 ± 0.04 7.26 ± 0.04 6.95 ± 0.04
Gl 791.2 A 0.286 ± 0.006 13.37 ± 0.03 . . . . . . . . .
Gl 831 A 0.2913 ± 0.0125 12.52 ± 0.06 . . . 7.36 ± 0.05 7.08 ± 0.05
Gl 644 Bb 0.3143 ± 0.0040 11.71 ± 0.10 . . . . . . . . .
Gl 623 A 0.3432 ± 0.0301 10.74 ± 0.05 7.19 ± 0.04 6.70 ± 0.04 6.46 ± 0.04
Gl 644 Ba 0.3466 ± 0.0047 11.22 ± 0.10 . . . . . . . . .
Gl 661 B 0.369 ± 0.035 11.15 ± 0.06 7.51 ± 0.04 7.02 ± 0.04 6.78 ± 0.05
Gl 570 C 0.3770 ± 0.0018 11.09 ± 0.17 7.40 ± 0.04 6.76 ± 0.04 6.57 ± 0.04
Gl 661 A 0.379 ± 0.035 11.10 ± 0.06 7.10 ± 0.05 6.56 ± 0.04 6.36 ± 0.05
GJ 2069 Ab 0.3987 ± 0.0007 12.57 ± 0.19 . . . . . . . . .
Gl 644 A 0.4155 ± 0.0057 10.76 ± 0.06 . . . 6.61 ± 0.05 6.35 ± 0.04
GJ 2069 Aa 0.4344 ± 0.0008 11.78 ± 0.18 . . . . . . . . .
Gl 570 B 0.5656 ± 0.0029 9.45 ± 0.05 6.21 ± 0.03 5.61 ± 0.03 5.39 ± 0.03
YYGem A 0.6028 ± 0.0014 9.03 ± 0.12 . . . . . . . . .
YYGem B 0.6069 ± 0.0014 9.38 ± 0.14 . . . . . . . . .
HD 195987 B 0.6650 ± 0.0079 7.91 ± 0.19 . . . 4.835 ± 0.059 4.702 ± 0.034
Gl 702 B 0.713 ± 0.029 7.52 ± 0.05 5.63 ± 0.05 . . . 4.53 ± 0.04
χ Dra B 0.750 ± 0.02 6.11 ± 0.27 . . . . . . . . .
GJ 765.2 B 0.763 ± 0.019 6.64 ± 0.05 4.94 ± 0.22 . . . 4.34 ± 0.22
GJ 765.2 A 0.831 ± 0.020 5.99 ± 0.04 4.40 ± 0.09 . . . 3.92 ± 0.09
HD 195987 A 0.844 ± 0.018 5.511 ± 0.028 . . . 3.679 ± 0.037 3.646 ± 0.033
a Data taken from Delfosse et al. (2000) and Torres et al. (2010).
KS as observables, we find masses of 0.614 ± 0.031 M⊙,
and 0.601 ± 0.031 M⊙, for WASP-43 and WASP-80, re-
spectively, slightly higher than the published values of
0.580 ± 0.050 M⊙ and 0.596 ± 0.035 M⊙. This same
method yields a mass of 0.534 ± 0.034 M⊙ for Kepler-
45, which is a bit lower than the published value of
0.570 ± 0.059 M⊙.
HATS-6b also has some of the deepest transits known,
with (Rp/R⋆)2
= 0.0323 ± 0.0003. There are only
two known planets with deeper transits than HATS-6b:
Kepler-45b ((Rp/R⋆)2
= 0.0362 ± 0.0054; Southworth
2012), and WTS-2b, a hot Jupiter on a very short pe-
riod orbit around a K2 dwarf star ((Rp/R⋆)2
= 0.0347 ±
0.0008; Birkby et al. 2014). One other system with
transit depths close to that of HATS-6 is WASP-80b
((Rp/R⋆)2
= 0.0292 ± 0.0001; Mancini et al. 2014). Fig-
ure 11 illustrates this as well, plotting the transit depth
vs. planet mass.
With an early M dwarf host star, HATS-6b receives
substantially less stellar irradiation than planets with the
same orbital period around Sun-like stars. As a result the
equilibrium temperature, assuming zero albedo, is a rel-
atively mild 712.8±5.1K. The atmospheric chemistry at
this temperature is expected to be notably different from
other hotter planets, with a greater abundance of CH4
and associated hydro-carbon hazes (Howe & Burrows
2012; Fortney et al. 2013). This makes HATS-6b a po-
tentially interesting target for studying the atmospheric
properties of a warm gas giant. In the bottom two pan-
els of Figure 11 we plot the approximate K-band trans-
mission spectrum S/N, and 4.5 µm occultation spectrum
S/N vs. Teq. In both cases we normalize the S/N to
that of the prototypical hot Jupiter HD 189733b. For
the transmission spectrum S/N we use the relation (e.g.,
Winn 2010):
S/N ∝
2RP HNH
R2
⋆
T14FK (10)
where H = kBTeq/µgP , µ is the mean molecular weight
(we assume 3.347 × 10−27
kg for a pure H2 atmosphere),
gP is the surface gravity of the planet, T14 is the tran-
sit duration, FK is the K-band flux of the star in Jan-
skys, and NH is a constant of order unity (we assume
1) depending on the particular spectroscopic feature un-
der consideration. The term
√
T14FK is included because
the photometric noise is proportional to 1/
√
FK and the
number of in transit measurements that can be made is
17. HATS-6b 17
TABLE 7
Fitted Parameters of Empirical Model for K and M
Dwarf Properties
Parameter Best Fit Value a Median and 1σ Uncertainty b
aρ,0 0.029 0.054+0.048
−0.049
aρ,1 −0.2924 −0.2989+0.0083
−0.0084
aρ,2 0.0817 0.0815+0.0020
−0.0020
aρ,3 −0.18187 −0.18280+0.00075
−0.00074
bm,0 35.3 32.6+3.1
−3.3
bm,1 −7.54 −7.09+0.44
−0.44
bm,2 1.17 1.24+0.10
−0.11
bm,3 −7.717 −7.690+0.034
−0.034
cV,0 1070 570+380
−370
cV,1 15.3 16.5+2.2
−2.9
cV,2 0.099 0.111+0.013
−0.013
cJ,0 130 100+150
−190
cJ,1 −5.0 −5.4+1.2
−1.1
cJ,2 −0.1154 −0.1105+0.0043
−0.0046
cH,0 −70 −130+150
−140
cH,1 −3.96 −3.46+0.96
−1.13
cH,2 −0.1619 −0.1615+0.0044
−0.0041
cK,0 50 −80+140
−140
cK,1 −5.08 −4.83+0.92
−0.99
cK,2 −0.1786 −0.1757+0.0039
−0.0038
SR 0.0069 0.0091+0.0010
−0.0012
SMbol 0.138 0.169+0.022
−0.025
a A self-consistent set of values corresponding to the maximum like-
lihood model.
b The median and 1σ confidence interval for each parameter as
determined from an MCMC analysis.
proportional to T14 (meaning the noise goes as 1/
√
T14).
We neglect the constant of proportionality on the right-
hand-side of eq. 10 needed to make the expression for
S/N unitless. For the occultation spectrum S/N we use
the relation (e.g., Winn 2010):
S/N ∝
RP
R⋆
2
exp(hc/kBλTeff) − 1
exp(hc/kBλTeq) − 1
T14F4.5 (11)
where h is Planck’s constant, c is the speed of light, kB is
Boltmann’s constant, Teff is the stellar effective temper-
ature, λ is the effective wavelength (we assume 4.5 µm),
and F4.5 is the 4.5 µm flux of the star in Janskys.
We find that HATS-6b has the highest expected S/N
transmission spectrum among known gas giant planets
with Teq < 750 K. Regarding occultations, HATS-6b
has the second highest expected S/N at 4.5 µm among
gas giant planets with Teq < 750 K after HD 80606b
(Laughlin et al. 2009, the expected S/N for HATS-6b is
∼ 50% that of HD 80606b).
Perhaps the most relevant planet for comparison is
WASP-80b, a hot Jupiter with Teq = 825 ± 20 K
(Mancini et al. 2014), with a similar transit depth
to HATS-6b, but orbiting a somewhat brighter star.
High-precision ground-based photometric transit obser-
vations of this system over several optical and near in-
frared band-passes have been presented by Mancini et al.
(2014) and Fukui et al. (2014), which have provided sug-
gestive evidence for the existence of a haze in the atmo-
sphere. The expected transmission S/N for HATS-6b is
approximately 0.4 times that of WASP-80b, so measur-
ing the transmission spectrum for HATS-6b will be chal-
lenging, but not out of reach for ground-based facilities.
HATS-6b is also a promising target for the NASA James
Webb Space Telescope mission, currently scheduled for
launch in 2018.
We checked whether the simultaneous optical multi-
filter GROND observations that we have already ob-
tained for HATS-6 can be used to probe the transmission
spectrum. We fit a Mandel & Agol (2002) transit model
to each of the GROND g, r, i and z light curves, fixing all
transit parameters to the best-fit values for the system,
except for Rp/R⋆, which we allow to vary independently
for each band-pass. We find that values for Rp/R⋆ val-
ues are consistent with a flat transmission spectrum, to
within the uncertainties. Additional observations would
be needed to detect spectroscopic features in the atmo-
sphere of HATS-6b.
In order to characterize the host star HATS-6 we have
also presented a new set of empirical stellar models ap-
plicable to main-sequence stars with M < 0.80 M⊙. We
use eclipsing binaries as well as resolved binaries with
masses and measured absolute magnitudes to determine
empirical relations between ρ⋆ and R (and thus ρ⋆ and
M), between M and Mbol, and between Teff and the
V , J, H and K-band bolometric corrections. We per-
form a global fit to the available data, determining the
intrinsic scatter in the relations in a self-consistent man-
ner. We find that from the density alone it is possible
to measure the mass of a ∼ 0.6 M⊙ star to ∼ 7% pre-
cision, and the radius to ∼ 2% precision. These pre-
cisions may be improved by up to a factor of two, to
∼ 3% and ∼ 1%, respectively, by incorporating addi-
tional photometric data. The relations presented here
are similar to those presented by Johnson et al. (2011)
and Johnson et al. (2012) except that we do not attempt
to incorporate metallicity directly into the model (it con-
tributes instead to the inherent scatter in the relations),
and we use a much larger sample of eclipsing binaries
than previously considered. Future improvements to our
model may be made by incorporating metallicity infor-
mation directly into the model, but this will require a
large sample of stars with measured masses, radii, abso-
lute magnitudes, and metallicities.
Finally, we note that the discovery of HATS-6b is a
demonstration of the enhanced sensitivity of HATSouth
to planets around low-mass K and M dwarf stars rela-
tive to other wide-field ground based surveys, such as
HATNet or WASP. The reason for this enhanced sensi-
tivity is the larger aperture optics used by HATSouth,
providing higher photometric precision for fainter stars.
HATSouth yields better than 2% precision, per 240 s in-
tegration, for stars down to r ∼ 14.5. For comparison, if
using the same integration time as HATSouth, HATNet
would yield 2% precision for stars with r 13. Based on
the TRILEGAL Galactic models (Girardi et al. 2005) we
estimate that there are ∼ 230000 stars with M < 0.6 M⊙,
r < 14.5 in the Southern sky, and at least 10◦
from the
Galactic disk that could be observed by HATSouth. This
is nearly a factor of ten more than the number of stars
with M < 0.6 M⊙ and r < 13.0 in the Northern sky that
could be observed by HATNet to the same photometric
precision. While in principle the discovery of HATS-6b
may be used to infer the occurrence rate of hot Jupiters
18. 18 Hartman et al.
TABLE 8
Transiting-planet hosting stars with similar properties to HATS-6.
Star Mass Radius V − K ρ⋆ Planet Mass Planet Period Reference
M⊙ R⊙ mag g cm−3 MJ day
GJ 3470 0.541 ± 0.067 0.503 ± 0.063 4.281 ± 0.030 6.0 ± 2.4 0.0441 ± 0.0053 3.34 1
WASP-80 0.596 ± 0.035 0.593 ± 0.012 3.53 ± 0.23 4.040 ± 0.012 0.562 ± 0.027 3.07 2,8
KIC 10905746 0.578 ± 0.032 0.548 ± 0.026 3.94 ± 0.24 4.97 ± 0.54 . . . 9.88 3
WASP-43 0.580 ± 0.050 0.598+0.034
−0.042 3.212 ± 0.027 3.81+0.86
−0.51 1.78 ± 0.10 0.81 4
Kepler-45 0.570 ± 0.059 0.539 ± 0.039 3.990 ± 0.058 5.12 ± 0.73 0.500 ± 0.061 2.46 5,9
HAT-P-54 0.645 ± 0.020 0.617 ± 0.013 3.179 ± 0.063 3.88 ± 0.27 0.760 ± 0.032 3.80 6
Kepler-26 0.650 ± 0.030 0.590 ± 0.030 3.352 ± 0.026 4.47 ± 0.71 . . . a 12.28 7
References. — 1: Bonfils et al. (2012); 2: Triaud et al. (2013b); 3: Fischer et al. (2012); 4: Hellier et al. (2011); 5: Johnson et al.
(2012); 6: Bakos et al. (2014); 7: Steffen et al. (2012); 8: Mancini et al. (2014); 9: Southworth (2012)
a The period listed is for Kepler-26b, the innermost of the four planets transiting this star.
TABLE 9
Stellar parameters for HATS-6
Parameter Value Isochrones a Value Empirical b Value Empirical b
Circ. Circ. Eccen.
Identifying Information
R.A. (h:m:s; 2MASS) 05h52m35.22s . . . . . .
Dec. (d:m:s; 2MASS) −19◦01′54.0′′ . . . . . .
2MASS ID 2MASS 05523523-1901539 . . . . . .
Spectroscopic properties c
Teff⋆ (K) . . . . . . . . . . . . 3770 ± 100 . . . . . .
[Fe/H] . . . . . . . . . . . . . . 0.200 ± 0.091 . . . . . .
Photometric properties
B (mag; APASS). . . . 16.664 ± 0.043 . . . . . .
V (mag; APASS). . . . 15.160 ± 0.024 . . . . . .
J (mag; 2MASS) . . . . 12.046 ± 0.024 . . . . . .
H (mag; 2MASS) . . . 11.397 ± 0.023 . . . . . .
Ks (mag; 2MASS) . . 11.224 ± 0.023 . . . . . .
Derived properties
M⋆ (M⊙) . . . . . . . . . . . 0.595 ± 0.017 0.574+0.020
−0.027 0.573 ± 0.031
R⋆ (R⊙) . . . . . . . . . . . . 0.5759 ± 0.0092 0.570 ± 0.011 0.567 ± 0.037
Teff⋆ (K) d . . . . . . . . . . 3872 ± 53 3724 ± 18 3722 ± 19
ρ⋆ (cgs) . . . . . . . . . . . . . 4.40 ± 0.13 4.36 ± 0.15 4.42+0.75
−0.47
log g⋆ (cgs). . . . . . . . . . 4.6920 ± 0.0077 4.683 ± 0.010 4.689 ± 0.038
L⋆ (L⊙) . . . . . . . . . . . . 0.0670 ± 0.0054 0.0558 ± 0.0024 0.0555 ± 0.0073
MV (mag) . . . . . . . . . . 9.43 ± 0.19 9.209 ± 0.075 9.22 ± 0.15
MK (mag,ESO) . . . . . 5.079 ± 0.065 5.387 ± 0.043 5.40 ± 0.14
Age (Gyr). . . . . . . . . . . 8.1 ± 4.3 . . . . . .
Distance (pc) . . . . . . . 172.6 ± 5.5 148.4 ± 3.3 147.8+7.0
−9.4
a Parameters based on combining the bulk stellar density determined from our fit to the light curves and
RV data for HATS-6, the effective temperature and metallicity from the Magellan/PFS spectrum, together
with the Dartmouth (Dotter et al. 2008) stellar evolution models. We perform the fit two ways: allowing
the eccentricity to vary (Eccen.), and keeping it fixed to zero (Circ.). The estimated value for ρ⋆ differs
significantly between these two fits. For the eccentric orbit fit the stellar density cannot be reproduced by
the Dartmouth models given the measured effective temperature and metallicity. We therefore only list
the parameters based on the Dartmouth models for the circular orbit fit.
b Parameters based on our empirical relations for K and M dwarf stellar properties, which are included
directly in our global modelling of the light curves and RV data for HATS-6. Again we perform the
fit two ways: allowing the eccentricity to vary, and keeping it fixed to zero. In this case including the
constraint from the observed V − K color of the star directly in the RV and light-curve modelling pulls
the free-eccentricity model to a lower eccentricity solution, yielding stellar parameters that are consistent
with those from the fixed-circular model.
c These parameters are determined from the I2-free Magellan/PFS spectrum of HATS-6 using the method
of Neves et al. (2014).
d The effective temperature listed here is derived from the Dartmouth stellar models, or from our
empirical stellar relations, and is not measured directly from the spectrum.
19. HATS-6b 19
TABLE 10
Orbital and planetary parameters
Parameter Value Isochrones a Value Empirical b Value Empirical b
Circ. Circ. Eccen.
Light curve parameters
P (days) . . . . . . . . . . . . . . . . . 3.3252721 ± 0.0000020 3.3252725 ± 0.0000021 3.3252726 ± 0.0000021
Tc (BJD) c . . . . . . . . . . . . . . 2456643.740560 ± 0.000089 2456643.740580 ± 0.000084 2456643.740600 ± 0.000094
T14 (days) c . . . . . . . . . . . . . 0.08497 ± 0.00036 0.08504 ± 0.00045 0.08508 ± 0.00037
T12 = T34 (days) c . . . . . . . 0.01542 ± 0.00035 0.01545 ± 0.00039 0.01549 ± 0.00034
a/R⋆ . . . . . . . . . . . . . . . . . . . . 13.70 ± 0.13 13.65 ± 0.15 13.71+0.73
−0.50
ζ/R⋆
d . . . . . . . . . . . . . . . . . . . 28.608 ± 0.066 28.612 ± 0.077 28.605 ± 0.066
Rp/R⋆ . . . . . . . . . . . . . . . . . . 0.17974 ± 0.00069 0.17978 ± 0.00077 0.17986 ± 0.00070
b ≡ a cos i/R⋆ . . . . . . . . . . . . 0.428+0.016
−0.022 0.427+0.020
−0.021 0.429+0.017
−0.020
i (deg) . . . . . . . . . . . . . . . . . . . 88.210 ± 0.093 88.210 ± 0.084 88.23 ± 0.16
Limb-darkening coefficients e
ag (linear term) . . . . . . . . . 0.4748 · · · · · ·
bg (quadratic term) . . . . . . 0.3277 · · · · · ·
ar (linear term) . . . . . . . . . . 0.4403 · · · · · ·
br (quadratic term) . . . . . . 0.3333 · · · · · ·
ai . . . . . . . . . . . . . . . . . . . . . . . 0.4092 · · · · · ·
bi . . . . . . . . . . . . . . . . . . . . . . . . 0.2831 · · · · · ·
az . . . . . . . . . . . . . . . . . . . . . . . 0.2843 · · · · · ·
bz . . . . . . . . . . . . . . . . . . . . . . . 0.3315 · · · · · ·
aR . . . . . . . . . . . . . . . . . . . . . . . 0.4091 · · · · · ·
bR . . . . . . . . . . . . . . . . . . . . . . . 0.3382 · · · · · ·
RV parameters
K (m s−1) . . . . . . . . . . . . . . . 68 ± 15 63 ± 14 64 ± 15√
e cos ω . . . . . . . . . . . . . . . . . . . . . . . 0.09 ± 0.19√
e sin ω . . . . . . . . . . . . . . . . . . . . . . . −0.03 ± 0.16
e cos ω . . . . . . . . . . . . . . . . . . . . . . . . . 0.015+0.085
−0.028
e sin ω . . . . . . . . . . . . . . . . . . . . . . . . . −0.004+0.031
−0.058
e . . . . . . . . . . . . . . . . . . . . . . . . 0, fixed 0, fixed 0.053 ± 0.060
ω . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 ± 120
PFS RV jitter (m s−1)f . . 26 ± 14 26 ± 11 26.2 ± 9.9
FEROS RV jitter (m s−1) 51 ± 56 41 ± 45 39 ± 41
HARPS RV jitter (m s−1) 0 ± 15 0 ± 20 0 ± 50
Planetary parameters
Mp (MJ) . . . . . . . . . . . . . . . . 0.357+0.059
−0.089 0.319 ± 0.070 0.321 ± 0.076
Rp (RJ) . . . . . . . . . . . . . . . . . 1.008 ± 0.019 0.998 ± 0.019 0.994 ± 0.065
C(Mp, Rp) g . . . . . . . . . . . . . −0.00 0.08 0.16
ρp (g cm−3) . . . . . . . . . . . . . 0.431+0.076
−0.111 0.399 ± 0.089 0.406+0.133
−0.098
log gp (cgs) . . . . . . . . . . . . . . 2.940+0.064
−0.130 2.90 ± 0.12 2.91 ± 0.12
a (AU) . . . . . . . . . . . . . . . . . . 0.03667 ± 0.00035 0.03623+0.00042
−0.00057 0.03621 ± 0.00065
Teq (K) . . . . . . . . . . . . . . . . . . 740 ± 12 712.8 ± 5.1 711 ± 18
Θh . . . . . . . . . . . . . . . . . . . . . . . 0.0436+0.0069
−0.0112 0.0404 ± 0.0089 0.0409 ± 0.0100
F (107erg s−1 cm−2) i . . 6.80 ± 0.44 5.84 ± 0.17 5.78 ± 0.60
a Parameters based on combining the bulk stellar density determined from our fit to the light curves and RV data for HATS-6,
the effective temperature and metallicity from the Magellan/PFS spectrum, together with the Dartmouth (Dotter et al. 2008)
stellar evolution models. We perform the fit two ways: allowing the eccentricity to vary (Eccen.), and keeping it fixed to zero
(Circ.). The estimated value for ρ⋆ differs significantly between these two fits. For the eccentric orbit fit the stellar density
cannot be reproduced by the Dartmouth models given the measured effective temperature and metallicity. We therefore only
list the parameters based on the Dartmouth models for the circular orbit fit.
b Parameters based on our empirical relations for K and M dwarf stellar properties, which are included directly in our global
modelling of the light curves and RV data for HATS-6. Again we perform the fit two ways: allowing the eccentricity to vary,
and keeping it fixed to zero. In this case including the constraint from the observed V − K color of the star directly in the
RV and light-curve modelling pulls the free-eccentricity model to a lower eccentricity solution, yielding parameters that are
consistent with those from the fixed-circular model. We adopt the empirical models, with fixed circular orbit, for our final
system parameters.
c Tc: Reference epoch of mid transit that minimizes the correlation with the orbital period. BJD is calculated from UTC.
T14: total transit duration, time between first to last contact; T12 = T34: ingress/egress time, time between first and second,
or third and fourth contact.
d Reciprocal of the half duration of the transit used as a jump parameter in our MCMC analysis in place of a/R⋆. It is related
to a/R⋆ by the expression ζ/R⋆ = a/R⋆(2π(1 + e sin ω))/(P
√
1 − b2
√
1 − e2) (Bakos et al. 2010).
e Values for a quadratic law given separately for the Sloan g, r, i, and z filters, as well as for the R filter. These values
were adopted from the tabulations by Claret (2004) assuming Teff = 3700 K and [Fe/H]= 0. We used the same limb darkening
coefficients for all four of the models shown here.
f The jitter was added in quadrature to the RV uncertainties and varied in the fit following (Hartman et al. 2012). We assumed
an independent jitter for each instrument.
g Correlation coefficient between the planetary mass Mp and radius Rp.
h The Safronov number is given by Θ = 1
2 (Vesc/Vorb)2
= (a/Rp)(Mp/M⋆) (see Hansen & Barman 2007).
i Incoming flux per unit surface area, averaged over the orbit.
20. 20 Hartman et al.
around early M dwarfs (e.g., Gaidos & Mann 2014), in
practice this requires a careful calibration of our transit
detection efficiency over the sample of M dwarfs that we
have observed. This is beyond the scope of the present
paper, but will be the subject of future work.
Development of the HATSouth project was funded
by NSF MRI grant NSF/AST-0723074, operations have
been supported by NASA grants NNX09AB29G and
NNX12AH91H, and follow-up observations receive par-
tial support from grant NSF/AST-1108686. A.J. ac-
knowledges support from FONDECYT project 1130857,
BASAL CATA PFB-06, and project IC120009 “Mil-
lennium Institute of Astrophysics (MAS)” of the Mil-
lenium Science Initiative, Chilean Ministry of Econ-
omy. R.B. and N.E. are supported by CONICYT-
PCHA/Doctorado Nacional. R.B. and N.E. acknowl-
edge additional support from project IC120009 “Mille-
nium Institute of Astrophysics (MAS)” of the Millen-
nium Science Initiative, Chilean Ministry of Economy.
V.S. acknowledges support form BASAL CATA PFB-06.
M.R. acknowledges support from FONDECYT postdoc-
toral fellowship 3120097. This work is based on obser-
vations made with ESO Telescopes at the La Silla Ob-
servatory. This paper also uses observations obtained
with facilities of the Las Cumbres Observatory Global
Telescope. Work at the Australian National Univer-
sity is supported by ARC Laureate Fellowship Grant
FL0992131. We acknowledge the use of the AAVSO Pho-
tometric All-Sky Survey (APASS), funded by the Robert
Martin Ayers Sciences Fund, and the SIMBAD database,
operated at CDS, Strasbourg, France. Operations at the
MPG 2.2 m Telescope are jointly performed by the Max
Planck Gesellschaft and the European Southern Obser-
vatory. The imaging system GROND has been built by
the high-energy group of MPE in collaboration with the
LSW Tautenburg and ESO. We thank R´egis Lachaume
for his technical assistance during the observations at
the MPG 2.2 m Telescope. We thank Helmut Steinle
and Jochen Greiner for supporting the GROND obser-
vations presented in this manuscript. We are grateful to
P.Sackett for her help in the early phase of the HATSouth
project.
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21. HATS-6b 21
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.1 1 10 100
(RP/RS)
2
MP [MJup]
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MP[MJup]
MS [MStar]
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4.5µmOccultationNormalizedS/N
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Fig. 11.— Comparison of the HATS-6 system to other known transiting exoplanet systems with MP > 0.1 MJ. In each case HATS-6
is indicated by the filled red triangle, while other objects are indicated by filled black circles. Top Left: Planet mass vs. transit depth as
measured by (Rp/R⋆)2. Top Right: Host star mass vs. planet mass. Bottom Left: Estimated S/N of a single occultation event at 4.5 µm
normalized to that of HD 189733b. Bottom Right: Estimated S/N of a transmission spectrum signal from one transit, assuming a pure H2
atmosphere, and observed at K-band, normalized to that of HD 189733b. HATS-6 has some of the deepest transits of known transiting
planet systems, it is also one of the lowest mass stars known to host a transiting gas giant planet. In terms of atmospheric characterization
it is one of the highest S/N targets with Teq < 750 K for both occultation and transmission spectroscopy.
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