The document presents an analysis of additional radial velocity measurements of the M dwarf stars Gl 433 and Gl 667C, obtained with the HARPS spectrograph. It finds:
- For Gl 433, one planet (Gl 433b) with a minimum mass of about 5.5 Earth masses and an orbital period of about 7 days. Longer period radial velocity variations are also detected, likely due to magnetic activity cycles.
- For Gl 667C, two planets are found. Gl 667Cb has a minimum mass of about 5.5 Earth masses and an orbital period of about 7 days. Gl 667Cc has a minimum mass of about 4.25 Earth masses and orbits in the habitable zone of its star with a
Large heterogeneities in_comet_67_p_as_revealed_by_active_pits_from_sinkhole_...Sérgio Sacani
Em um estudo publicado online na edição da revista Nature, 18 cavidades quase circulares foram identificadas no hemisfério norte do cometa 67P/Churyumov-Gerasimenko. As cavidades tem de dezenas a centenas de metros de diâmetro e se estendem a mais de 210 metros abaixo da superfície do cometa. Essas cavidades são ativas e provavelmente criadas por um processo de sumidouro, possivelmente acompanhado por explosões.
A sonda Rosetta da ESA tem monitorado a atividade do cometa por mais de um ano, observando como seu halo de poeira e gás cresce à medida que o cometa se move para perto do Sol ao longo de sua órbita.
De uma distância de apenas centenas de quilômetros, a sonda observa um intrigante padrão de jatos de poeira sendo emitidos do núcleo enquanto eles são ejetados para o espaço.
Mas agora, graças a imagens de alta resolução da câmera de ângulo restrito da sonda, a Optical Spectroscopic and Infrared Remote Imaging System (OSIRIS), feitas de uma distância entre 10 a 30 km do centro do cometa, alguns desses jatos puderam ser rastreados de volta à superfície do cometa, chegando até a sua fonte, é a primeira vez que isso é feito e observado.
Large heterogeneities in_comet_67_p_as_revealed_by_active_pits_from_sinkhole_...Sérgio Sacani
Em um estudo publicado online na edição da revista Nature, 18 cavidades quase circulares foram identificadas no hemisfério norte do cometa 67P/Churyumov-Gerasimenko. As cavidades tem de dezenas a centenas de metros de diâmetro e se estendem a mais de 210 metros abaixo da superfície do cometa. Essas cavidades são ativas e provavelmente criadas por um processo de sumidouro, possivelmente acompanhado por explosões.
A sonda Rosetta da ESA tem monitorado a atividade do cometa por mais de um ano, observando como seu halo de poeira e gás cresce à medida que o cometa se move para perto do Sol ao longo de sua órbita.
De uma distância de apenas centenas de quilômetros, a sonda observa um intrigante padrão de jatos de poeira sendo emitidos do núcleo enquanto eles são ejetados para o espaço.
Mas agora, graças a imagens de alta resolução da câmera de ângulo restrito da sonda, a Optical Spectroscopic and Infrared Remote Imaging System (OSIRIS), feitas de uma distância entre 10 a 30 km do centro do cometa, alguns desses jatos puderam ser rastreados de volta à superfície do cometa, chegando até a sua fonte, é a primeira vez que isso é feito e observado.
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.
The habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
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.
The habitability of Proxima Centauri b - I. Irradiation, rotation and volatil...Sérgio Sacani
Proxima b is a planet with a minimum mass of 1.3 M⊕ orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass,
active star and the Sun’s closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b
and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet
and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time
evolution of the star’s spectrum, which is essential for modeling the flux received over Proxima b’s lifetime. We also show that Proxima
b’s obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet’s eccentricity and
level of triaxiality. Next we consider the evolution of Proxima b’s water inventory. We use our spectral energy distribution to compute
the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find
that Proxima b is likely to have lost less than an Earth ocean’s worth of hydrogen (EOH) before it reached the HZ 100–200 Myr after
its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We
conclude that Proxima b is a viable candidate habitable planet.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
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.
Um dos artigos da edição especial da revista Science, mostrando as alterações nas propriedades do cometa Churyumov-Gerasimenko, à medida que ele se aproxima do Sol.
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
We present the first results of the eXtreme UV Environments (XUE) James Webb Space Telescope (JWST)
program, which focuses on the characterization of planet-forming disks in massive star-forming regions. These
regions are likely representative of the environment in which most planetary systems formed. Understanding the
impact of environment on planet formation is critical in order to gain insights into the diversity of the observed
exoplanet populations. XUE targets 15 disks in three areas of NGC 6357, which hosts numerous massive OB stars,
including some of the most massive stars in our Galaxy. Thanks to JWST, we can, for the first time, study the effect
of external irradiation on the inner (<10 au), terrestrial-planet-forming regions of protoplanetary disks. In this study,
we report on the detection of abundant water, CO, 12CO2, HCN, and C2H2 in the inner few au of XUE 1, a highly
irradiated disk in NGC 6357. In addition, small, partially crystalline silicate dust is present at the disk surface. The
derived column densities, the oxygen-dominated gas-phase chemistry, and the presence of silicate dust are
surprisingly similar to those found in inner disks located in nearby, relatively isolated low-mass star-forming
regions. Our findings imply that the inner regions of highly irradiated disks can retain similar physical and chemical
conditions to disks in low-mass star-forming regions, thus broadening the range of environments with similar
conditions for inner disk rocky planet formation to the most extreme star-forming regions in our Galaxy.
An irradiated-Jupiter analogue hotter than the SunSérgio Sacani
Planets orbiting close to hot stars experience intense extreme-ultraviolet
radiation, potentially leading to atmosphere evaporation and to thermal
dissociation of molecules. However, this extreme regime remains mainly
unexplored due to observational challenges. Only a single known ultra-hot
giant planet, KELT-9b, receives enough ultraviolet radiation for molecular
dissociation, with a day-side temperature of ~4,600 K. An alternative
approach uses irradiated brown dwarfs as hot-Jupiter analogues. With
atmospheres and radii similar to those of giant planets, brown dwarfs
orbiting close to hot Earth-sized white dwarf stars can be directly detected
above the glare of the star. Here we report observations revealing
an extremely irradiated low-mass companion to the hot white dwarf
WD 0032–317. Our analysis indicates a day-side temperature of ~8,000 K,
and a day-to-night temperature difference of ~6,000 K. The amount of
extreme-ultraviolet radiation (with wavelengths 100–912 Å) received by
WD 0032–317B is equivalent to that received by planets orbiting close to stars
as hot as late B-type stars, and about 5,600 times higher than that of KELT-9b.
With a mass of ~75–88 Jupiter masses, this near-hydrogen-burning-limit
object is potentially one of the most massive brown dwarfs known.
TOI-5678 b: A 48-day transiting Neptune-mass planet characterized with CHEOPS...Sérgio Sacani
A large sample of long-period giant planets has been discovered thanks to long-term radial velocity surveys, but only a few
dozen of these planets have a precise radius measurement. Transiting gas giants are crucial targets for the study of atmospheric composition across a wide range of equilibrium temperatures and, more importantly, for shedding light on the formation and evolution
of planetary systems. Indeed, compared to hot Jupiters, the atmospheric properties and orbital parameters of cooler gas giants are
unaltered by intense stellar irradiation and tidal effects.
Aims. We aim to identify long-period planets in the Transiting Exoplanet Survey Satellite (TESS) data as single or duo-transit events.
Our goal is to solve the orbital periods of TESS duo-transit candidates with the use of additional space-based photometric observations
and to collect follow-up spectroscopic observations in order to confirm the planetary nature and measure the mass of the candidates.
Methods. We use the CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability period aliases in order to discard or confirm a transit event at a given period. Once a period is confirmed, we jointly model the TESS and CHEOPS light curves
along with the radial velocity datasets to measure the orbital parameters of the system and obtain precise mass and radius measurements.
Results. We report the discovery of a long-period transiting Neptune-mass planet orbiting the G7-type star TOI-5678. Our spectroscopic analysis shows that TOI-5678 is a star with a solar metallicity. The TESS light curve of TOI-5678 presents two transit events
separated by almost two years. In addition, CHEOPS observed the target as part of its Guaranteed Time Observation program. After
four non-detections corresponding to possible periods, CHEOPS detected a transit event matching a unique period alias. Follow-up
radial velocity observations were carried out with the ground-based high-resolution spectrographs CORALIE and HARPS. Joint modeling reveals that TOI-5678 hosts a 47.73 day period planet, and we measure an orbital eccentricity consistent with zero at 2σ. The
planet TOI-5678 b has a mass of 20 ± 4 Earth masses (M⊕) and a radius of 4.91 ± 0.08 R⊕. Using interior structure modeling, we find
that TOI-5678 b is composed of a low-mass core surrounded by a large H/He layer with a mass of 3.2
+1.7
−1.3 M⊕.
Conclusions. TOI-5678 b is part of a growing sample of well-characterized transiting gas giants receiving moderate amounts of stellar
insolation (11 S ⊕). Precise density measurement gives us insight into their interior composition, and the objects orbiting bright stars
are suitable targets to study the atmospheric composition of cooler gas giants.
Similar to The harps serach_for_southern_exoplanets_02 (20)
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.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
zkStudyClub - Reef: Fast Succinct Non-Interactive Zero-Knowledge Regex ProofsAlex Pruden
This paper presents Reef, a system for generating publicly verifiable succinct non-interactive zero-knowledge proofs that a committed document matches or does not match a regular expression. We describe applications such as proving the strength of passwords, the provenance of email despite redactions, the validity of oblivious DNS queries, and the existence of mutations in DNA. Reef supports the Perl Compatible Regular Expression syntax, including wildcards, alternation, ranges, capture groups, Kleene star, negations, and lookarounds. Reef introduces a new type of automata, Skipping Alternating Finite Automata (SAFA), that skips irrelevant parts of a document when producing proofs without undermining soundness, and instantiates SAFA with a lookup argument. Our experimental evaluation confirms that Reef can generate proofs for documents with 32M characters; the proofs are small and cheap to verify (under a second).
Paper: https://eprint.iacr.org/2023/1886
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Enhancing Performance with Globus and the Science DMZGlobus
ESnet has led the way in helping national facilities—and many other institutions in the research community—configure Science DMZs and troubleshoot network issues to maximize data transfer performance. In this talk we will present a summary of approaches and tips for getting the most out of your network infrastructure using Globus Connect Server.
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
Le nuove frontiere dell'AI nell'RPA con UiPath Autopilot™UiPathCommunity
In questo evento online gratuito, organizzato dalla Community Italiana di UiPath, potrai esplorare le nuove funzionalità di Autopilot, il tool che integra l'Intelligenza Artificiale nei processi di sviluppo e utilizzo delle Automazioni.
📕 Vedremo insieme alcuni esempi dell'utilizzo di Autopilot in diversi tool della Suite UiPath:
Autopilot per Studio Web
Autopilot per Studio
Autopilot per Apps
Clipboard AI
GenAI applicata alla Document Understanding
👨🏫👨💻 Speakers:
Stefano Negro, UiPath MVPx3, RPA Tech Lead @ BSP Consultant
Flavio Martinelli, UiPath MVP 2023, Technical Account Manager @UiPath
Andrei Tasca, RPA Solutions Team Lead @NTT Data
Welcome to the first live UiPath Community Day Dubai! Join us for this unique occasion to meet our local and global UiPath Community and leaders. You will get a full view of the MEA region's automation landscape and the AI Powered automation technology capabilities of UiPath. Also, hosted by our local partners Marc Ellis, you will enjoy a half-day packed with industry insights and automation peers networking.
📕 Curious on our agenda? Wait no more!
10:00 Welcome note - UiPath Community in Dubai
Lovely Sinha, UiPath Community Chapter Leader, UiPath MVPx3, Hyper-automation Consultant, First Abu Dhabi Bank
10:20 A UiPath cross-region MEA overview
Ashraf El Zarka, VP and Managing Director MEA, UiPath
10:35: Customer Success Journey
Deepthi Deepak, Head of Intelligent Automation CoE, First Abu Dhabi Bank
11:15 The UiPath approach to GenAI with our three principles: improve accuracy, supercharge productivity, and automate more
Boris Krumrey, Global VP, Automation Innovation, UiPath
12:15 To discover how Marc Ellis leverages tech-driven solutions in recruitment and managed services.
Brendan Lingam, Director of Sales and Business Development, Marc Ellis
The Metaverse and AI: how can decision-makers harness the Metaverse for their...Jen Stirrup
The Metaverse is popularized in science fiction, and now it is becoming closer to being a part of our daily lives through the use of social media and shopping companies. How can businesses survive in a world where Artificial Intelligence is becoming the present as well as the future of technology, and how does the Metaverse fit into business strategy when futurist ideas are developing into reality at accelerated rates? How do we do this when our data isn't up to scratch? How can we move towards success with our data so we are set up for the Metaverse when it arrives?
How can you help your company evolve, adapt, and succeed using Artificial Intelligence and the Metaverse to stay ahead of the competition? What are the potential issues, complications, and benefits that these technologies could bring to us and our organizations? In this session, Jen Stirrup will explain how to start thinking about these technologies as an organisation.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
Removing Uninteresting Bytes in Software FuzzingAftab Hussain
Imagine a world where software fuzzing, the process of mutating bytes in test seeds to uncover hidden and erroneous program behaviors, becomes faster and more effective. A lot depends on the initial seeds, which can significantly dictate the trajectory of a fuzzing campaign, particularly in terms of how long it takes to uncover interesting behaviour in your code. We introduce DIAR, a technique designed to speedup fuzzing campaigns by pinpointing and eliminating those uninteresting bytes in the seeds. Picture this: instead of wasting valuable resources on meaningless mutations in large, bloated seeds, DIAR removes the unnecessary bytes, streamlining the entire process.
In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
SAP Sapphire 2024 - ASUG301 building better apps with SAP Fiori.pdfPeter Spielvogel
Building better applications for business users with SAP Fiori.
• What is SAP Fiori and why it matters to you
• How a better user experience drives measurable business benefits
• How to get started with SAP Fiori today
• How SAP Fiori elements accelerates application development
• How SAP Build Code includes SAP Fiori tools and other generative artificial intelligence capabilities
• How SAP Fiori paves the way for using AI in SAP apps
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
1. Astronomy & Astrophysics manuscript no. paper677˙433 c ESO 2012
February 14, 2012
The HARPS search for southern extra-solar planets. XXXV.
Super-Earths around the M-dwarf neighbors Gl 433 and Gl 667C ⋆
X. Delfosse1 , X. Bonfils1 , T. Forveille1 , S. Udry2 , M. Mayor2 , F. Bouchy3 , M. Gillon4 , C. Lovis2 , V. Neves1,5,6 , F.
Pepe2 , C. Perrier1 , D. Queloz2 , N.C. Santos5,6 , and D. S´ gransan2
e
1
UJF-Grenoble 1 / CNRS-INSU, Institut de Plan´ tologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, F-38041,
e
France
2
Observatoire de Gen` ve, Universit´ de Gen` ve, 51 ch. des Maillettes, 1290 Sauverny, Switzerland
e e e
3
Institut d’Astrophysique de Paris, CNRS, Universit´ Pierre et Marie Curie, 98bis Bd. Arago, 75014 Paris, France
e
arXiv:1202.2467v1 [astro-ph.EP] 11 Feb 2012
4
Universit de Li` ge, All´ e du 6 aoˆ t 17, Sart Tilman, Li` ge 1, Belgium
e e u e
5
Centro de Astrof´sica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
ı
6
Departamento de F´sica e Astronomia, Faculdade de Ciˆ ncias, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto,
ı e
Portugal
Received / Accepted
ABSTRACT
Context. M dwarfs have been found to often have super-Earth planets with short orbital periods. Such stars are thus preferential targets
in searches for rocky or ocean planets in the solar neighbourhood.
Aims. In a recent paper (Bonfils et al. 2011), we announced the discovery of respectively 1 and 2 low mass planets around the M1.5V
stars Gl 433 and Gl 667C. We found those planets with the HARPS spectrograph on the ESO 3.6-m telescope at La Silla Observatory,
from observations obtained during the Guaranteed Time Observing program of that instrument.
Methods. We have obtained additional HARPS observations of those two stars, for a total of respectively 67 and 179 Radial Velocity
measurements for Gl 433 and Gl 667C, and present here an orbital analysis of those extended data sets and our main conclusion about
both planetary systems.
Results. One of the three planets, Gl 667Cc, has a mass of only M2 . sin i ∼ 4.25 M⊕ and orbits in the central habitable zone of its host
star. It receives just 10% less stellar energy from Gl 667C than the Earth receives from the Sun. However planet evolution in habitable
zone can be very different if the host star is a M dwarf or a solar-like star, without necessarily questioning the presence of water. The
two other planets, Gl 433b and Gl 667Cb, both have M2 . sin i of ∼5.5 M⊕ and periods of ∼7 days. The Radial Velocity measurements
of both stars contain longer time scale signals, which we fit as longer period Keplerians. For Gl 433 that signal probably originates
in a Magnetic Cycle, while a longer time span will be needed to conclude for Gl 667C. The metallicity of Gl 433 is close to solar,
while Gl 667C is metal poor with [Fe/H]∼-0.6. This reinforces the recent conclusion that the occurence of Super-Earth planets does
not strongly correlate with stellar metallicity.
Key words. techniques : radial velocity / stars : late-type / planetary systems
1. Introduction P<10 days, to be compared to ∼ 50% for similar planets around
G dwarfs.
Much interest has recently focused on planets around M dwarfs, The physical conditions in the circumstellar disks of very
with three main motivations: constraining formation, physico- low mass stars therefore favor the formation of low-mass planets
chemical characterization of planets, and finding rocky planets (rocky and maybe ocean planets) close to the star. This translates
in the habitable zone of their stars. The compared occurence fre- into good odds for finding telluric planets transiting M dwarfs
quency, as a function of orbital elements, of planets around M (like those very recently announced by Muirhead et al. 2012).
dwarfs and around the more massive solar-type stars probes the Such transiting planets are excellent atmospheric characteriza-
sensitivity of planetary formation to its initial conditions. Giant tion targets: since transit depth scales with the squared stellar
planets are rare around M dwarfs, with Bonfils et al. (2011a), radius, a transit across an M dwarf provides much more accurate
for instance, finding a low frequency of 6+6 % for periods under
−2 measurements of radius and transmission spectrum than across
10000 days. That number is lower than the 10±2% frequency for a solar-type star.
similar planets around solar-like stars (e.g. Mayor et al. 2011),
though not yet at a high significance level. Super-Earth (2- Finding rocky planets in the habitable zone (HZ) of their
10M⊕ ), by contrast, seem abundant around M dwarfs at the short stars is another motivation for planet searches around M dwarfs.
orbital periods to which radial velocity searches are most sensi- Planets of given mass and orbital separation induce larger stel-
tive: Bonfils et al. (2011a) find an occurence rate of 88+55 % for lar radial velocity variation around lower mass stars, but, more
−19
importantly, the low luminosity of M dwarfs moves their habit-
able zone much nearer to the star. These two effects combine,
⋆
Based on observations collected with HARPS instrument on and a habitable planet around a 0.3-M⊙ M dwarf produces a
the 3.6-m telescope at La Silla Observatory (European Southern 7 times larger radial velocity wobble than the same planet or-
Observatory) under programs ID072.C-0488(E) biting a solar-mass G dwarf. Additionally, some atmospheric
1
2. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
models suggest additional advantages of planets in the HZ of M
dwarfs for habitability characterization: Segura et al. (2005) find
that the significant dependence of atmospheric photochemistry
on the incoming spectral energy distribution strongly reinforces
some biomarkers in the spectra of Earth-twin planets orbiting M
dwarfs. N2 O and CH3 Cl, in particular, would be detectable for
Earth-twin planets around M dwarfs but not around solar-type
stars.
As discussed in Bonfils et al. (2011a), which presents the
full specifications of the survey, we have been monitoring the
radial velocities (RV) of a distance and magnitude limited sam-
ple of 102 M dwarfs since 2003 with the HARPS spectrograph
mounted on the ESO/3.6-m La Silla telescope. With a typical RV
accuracy of 1-3m/s and 460 hours of observations, our survey
identified super-Earth and Neptune-like planets around Gl 176
(Forveille et al. 2009), Gl 581 (Bonfils et al. 2005b; Udry et al.
2007; Mayor et al. 2009) and Gl 674 (Bonfils et al. 2007). In
Bonfils et al. (2011a), which was centered on the statistical im-
plications of the survey for planet populations, we added to this Fig. 1. Emission reversal in the Ca II H line in the average
list 1 planet around Gl 433 and 2 around Gl 667C, providing de- spectra of (from the less to the more active) Gl 581 (M3, in
tailed periodograms and a false alarm probability in using our magenta), Gl 667C (M1.5, in pink), Gl 433 (M1.5, in yellow),
GTO/HARPS data. Anglada-Escud´ et al. (2012) recently an-
e Gl 176(M2.5, dark) and Gl 674 (M3, in blue). Within our 100
nounced a confirmation of the planets Gl 667Cb and Gl 667Cc, M dwarfs sample, Gl 581 has one of the weakest Ca II emission
which however is only very partly independent, since it largely and illustrates a very quiet M dwarf. Gl 674 and Gl 176 have
rests on our Bonfils et al. (2011a) observations and data reduc- a much stronger emission and are both moderately active with
tion. an identified rotational period of respectively 35 and 39 days
Here we present a more detailed orbital analysis of these two (Bonfils et al. 2007; Forveille et al. 2009).
systems than we could present in Bonfils et al. (2011a), and we
refine their parameters by adding new seasons of RV measure-
ments. The 3 super-Earths have M2 . sin i between 4.25 and 5.8
M⊕ . With periods of ∼7days, both Gl433b and Gl667Cb are hot For homogeneity, we reprocessed all spectra with the lat-
super-Earths. Gl667Cc, by contrast, has a 28-day period. It or- est version of the standard HARPS pipeline. The pipeline
bits in the centre of the habitable zone of its star, and receives just (Lovis & Pepe 2007) uses a nightly set of calibration exposures
10% less stellar energy than the Earth receives from the Sun. We to locate the orders, flat-field the spectra (Tungsten lamp illu-
also detect some longer-period radial-velocity variations, which mination) and to precisely determine the wavelength calibration
we also discuss. scale (ThAr lamp exposure). We measured the Radial Velocity
The next section discusses our data taking and analysis, through cross correlation of the stellar spectra with a numerical
while Sect. 3 summarizes the stellar characteristics of Gl 433 weighted mask, following the procedure of Pepe et al. (2002).
and Gl 667C. Sect. 4 and 5 respectively present our orbital anal- For both Gl 433 and Gl667C, we used a mask derived from a
yses of the planetary systems of Gl 433 and Gl 667C. Sect. 6 very high S/N spectrum of a M2 dwarf. The velocities of Gl 433
discusses the habitable zones of M dwarfs, with emphasis on the and Gl 667C have internal median errors of respectively 1.15 and
case of Gl 667Cc. Finally, Sect.7. summarizes our conclusions.
1.30 m/s. This includes the uncertainty of the nightly zero point
calibration, the drift and jitter of the wavelength scale during a
2. Spectroscopic and Doppler measurement with night, and the photon noise (the dominant term here).
HARPS Because both stars have significant proper motion, the pro-
jection of their velocity vector changes over the duration of our
Our observing procedure is presented in some details in
survey. We subtract this secular acceleration (see K¨ rster et al.
u
Bonfils et al. (2011a), and is only summarized here. For both
2003, for details) before radial velocity analysis. For Gl 433 and
stars we obtained 15 min exposures with the HARPS spec-
Gl 667C the values are respectively 0.15 and 0.21 m/s/yr.
trograph (High Accuracy Radial velocity Planets Searcher
Mayor et al. 2003). HARPS is a fixed-format echelle spectro-
graph, which covers the 380 to 630 nm spectral range with a re-
solving power of 115 000. HARPS is fed by a pair of fibres, and 3. Stellar characteristic of Gl 433 and Gl 667C
is optimized for high accuracy radial-velocity measurements,
with a stability better than 1m/s during one night. To avoid light Both Gl 433 (LHS 2429) and Gl 667C are early-M dwarfs in
pollution on the stellar spectrum of our “faint” M-dwarf targets, the close solar neighborhood. Table 1 summarizes their proper-
we chose to keep dark the calibration fiber of the spectrograph. ties. The masses are computed from the K-band absolute mag-
Our Radial Velocity accuracy is therefore intrinsically limited nitudes using the Delfosse et al. (2000) empirical near-infrared
by the instrumental stabiliy of HARPS. That stability is however mass-luminosity relation. The bolometric correction of Gl 433,
excellent and the signal-to-noise ratio of our 15min exposures and then its luminosity, is computed from the I − K color us-
of these two V∼10 M dwarfs limits the RV precision to slightly ing the cubic polynomial of Leggett et al. (2000). Those authors
above 1 m/s (the median S/N ratio per pixel at 550nm is 57 and directly determined the luminosity of Gl 667C using a combi-
65 respectively for Gl 433 and Gl 667C). Sect. 4 and 5 discuss nation of flux calibrated observed spectra and synthetic spectra,
the number of exposures and their time span for the two stars. and we adopt their value.
2
3. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
Gl 433 Gl 667C tance of 32.4” of Gl 667AB, giving an expected semi-major axis
(1)
Spectral type M1.5 M1.5 of ∼300 A.U. (for a distance of 7.23 pc and a factor of 1.26 be-
V 9.79 10.22 tween expected and projected semi-major axis, Fischer & Marcy
J(2) 6.47±0.02 6.85±0.02 1992).
H(2) 5.86±0.04 6.32±0.04 The Bonfils et al. (2005a) photometric relationship for
K(2) 5.62±0.02 6.03±0.02 Gl667C gives us an estimate of the metallicity of 0.55
π 110.6±1.8(3) 138.2±0.7(4)
dex, which agrees quite well with the spectroscopic deter-
M (in M⊙ )(5) 0.48 0.33
L (in L⊙ )(6) 0.034 0.014
mination of [Fe/H]∼-0.6 for the primary (Perrin et al. 1988;
[Fe/H](7) -0.22 -0.55 Zakhozhaj & Shaparenko 1996). This demonstrates that the
Teff (8) 3600 3600 Bonfils et al. (2005a) photometric calibration gives excellent re-
log RX (9) <-4.8 <-4.12 sults for low-metallicity M dwarfs. The Neves et al. (2012) rela-
tionship gives [Fe/H]∼-0.45, confirming that this star is a metal-
Table 1. (1) Hawley et al. (1996); (2) Cutri et al. (2003); (3) poor M dwarfs.
Perryman et al. (1997); (4) S¨ derhjelm (1999); (5) from mass-
o
Consistent with this chemical composition, Gl667 is classi-
luminosity relation of Delfosse et al. (2000) ; (6) Leggett et al. fied as member of the old disk population from its UVW veloc-
(2000); (7) from luminosity-color relation of Bonfils et al.
ity (Leggett 1992) and is among the objects of lower chromo-
(2005a); (8) Morales et al. (2008); (9) from Schmitt et al. (1995)
spheric emission for its luminosity (Rauscher & Marcy 2006).
for Gl 433 and from Schmitt & Liefke (2004) for Gl 667C In the Fig. 1 the Ca II H line emission of Gl 667C is slightly
inferior to the Gl 433 one, also indicating also a large rotational
period.
3.1. Gl 433 : metallicity, activity and dynamic population The NEXXUS database (Schmitt & Liefke 2004) indicates
detection of the X-ray emission of Gl 667C from the ROSAT
According to Bonfils et al. (2005a) we estimated the metallic- All-Sky Survey (RASS) with a value of log LX = 27.89. But the
ity of Gl 433 to [Fe/H]∼-0.2. This photometric calibration rela- resolution of ROSAT image is not sufficient to separate the three
tionship is based on a faint number of stars in the high metal- components of the system. Although this value is the jointed flux
licity range but Neves et al. (2012) show that for such value for Gl 667ABC, it gives a superior limit on the coronal emis-
of [Fe/H] the calibration is correct with a typical dispersion of sion of Gl 667C. This implies RX = LogLX /LBOL well below
0.2 dex. This is confirmed by the value of [Fe/H]=-0.13 obtained −4.12 and rotational period superior to 40 days (in applying the
in using Neves et al. (2012) relationship, itself an update from Kiraga & Stepien (2007) RX versus rotation period relationship).
Schlaufman & Laughlin (2010). We could conclude that Gl 433
is solar or slightly sub-metallic.
Gl 433 is dynamically classified as a membership of old disk 4. Orbital analysis of Gl 433
(Leggett 1992). Ca II H and K chromospheric emission is de- 4.1. HARPS measurements
termined by Rauscher & Marcy (2006) and Gl 433 is in the less
active half of M dwarfs with same luminosity. For objects of We obtained 67 measurements of Gl433 radial velocity that span
similar spectral type a direct comparison of Ca II emission lines 2904 days from December 2003 to November 2011. The data
gives relative estimation of rotational period (larger Ca II emis- add 17 new points to those analyzed in Bonfils et al. (2011a) and
sions correspond to shorter rotational periods). In the Fig 1 we extend their time span by 1200 days. We estimate that the uncer-
present an average HARPS spectrum of Gl 433 in the region of tainties of ∼1.1 m/s are dominated by photon noise (the median
Ca II H line. Gl 433 has an emission of Ca II slightly higher S/N ratio per pixel at 550 nm is 57). Overall, the RVs have a
than Gl 581 (a very quite M dwarf), but well below those of rms=3.14 m/s and χ2 = 7.7 ± 0.5 per degree of freedom, con-
Gl 176 and Gl 674 for whose rotational periods of respectively firming variability in excess to measurement uncertainties (∼1.1
35 and 39 days have been determined by Bonfils et al. (2007) m/s, dominated by photon noise).
and Forveille et al. (2009). The five M dwarfs of the Fig. 1 do We therefore continued with a classical periodicity analy-
not have identical spectral (from M1.5 to M3) therefore estima- sis, based on floating-mean periodograms (Gilliland & Baliunas
tion of rotation from the Ca II emission is only indicative. It 1987; Zechmeister et al. 2009). Fig. 2 (bottom panel) depicts the
shows that Gl 433 rotates most probably with a period longer periodogram of our RV time series and shows a strong power
than Gl 176 and Gl 674. excess around the period 7.3 day. We plot the window function
The X-ray flux of Gl 433 is not detected by ROSAT and in Fig. 2 (middle panel) to identify the typical time sampling but
we use a ROSAT limiting sensitivity of 2.527 .[d/10pc]2 erg/s found no counter part to this periodicity. We adopted the normal-
(Schmitt et al. 1995) to estimate RX = LogLX /LBOL < −4.8. For ization of periodograms proposed by Zechmeister et al. (2009),
an M dwarfs of ∼ 0.5M⊙ the RX versus rotation period relation which is such that a power of 1 means that a sine function is a
of Kiraga & Stepien (2007) give Prot > 40 days for such level perfect fit to the data, whereas a power of 0 indicates no improve-
of X flux. This inferior limit on the rotation period is coherent ment over a constant model. Hence, the most powerful peak was
with the estimate from the Ca II emission. measured at a period P∼7.3 days with a power pmax = 0.51.
To assess its fortuity we performed a bootstrap randomization
3.2. Gl 667C : multiplicity, metallicity, activity and dynamic (Press et al. 1992): we generated 10,000 virtual data sets by
population shuffling the actual radial velocities and retaining the dates; for
each set we computed a periodogram; with all periodograms we
Gl 667C is the lightest and isolated component of a hierarchical built a distribution of power maxima. It appears that, in ran-
triple system, the two others components are a closest couple of dom data sets, power maxima exceed p = 0.40 only once every
K dwarfs. Gl 667AB has a semi-major axis of 1.82 A.U. (pe- 100 trials, and never exceed p = 0.43 over 10,000 trials. This
riod of 42.15 years) and a total mass dynamically determined suggests a False Alarm Probability (FAP) < 1/10, 000 for the
of 1.27M⊙ (S¨ derhjelm 1999). Gl 667C is at a projected dis-
o 7.3-d period seen in the original periodogram. Moreover, for a
3
4. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
(Table 2). The rms and χ2 around the solution decreased to
2.17 m/s and 2.00 ± 0.09 per degree of freedom, respectively.
Inspecting the residuals and their periodogram, we measured
the power of the most powerful peak (P ∼2900 d; pmax = 0.28)
and apply bootstrap randomization to find it is insignificant
(FAP = 22%). We nevertheless found that adding a quadratic
drift to the 1-planet model did improve the solution (rms=1.91
m/s and χ2 = 1.79 ± 0.09 per degree of freedom).
4.2. HARPS+UVES measurements
Radial velocity measurements of Gl 433 were also obtained with
UVES by Zechmeister et al. (2009). They span 2553 days be-
tween March 2000 and March 2007 and can therefore extend the
time span of our observations by more than 3 years (see Fig. 3 -
second panel).
Hence we pooled together UVES and HARPS data and
performed again a 1 planet fit with Yorbit. We converged on
the same solution with more precise orbital parameters (P =
7.37131 ± 0.00096 d; K1 = 2.846 ± 0.248 m/s; e = 0.13 ± 0.09).
The residuals around the solution show a power excess at a sim-
ilar period than before (P ∼2857 d; pmax = 0.19) that now ap-
pears more significant. With 10,000 trials of bootstrap random-
ization we found a FAP ∼ 0.2%. Although such signal requires
additional measurements for confirmation it justified the addi-
tion of a second planet to our model.
With a model composed of 2 planets on Keplerian orbits,
Yorbit converges on periods of 7.37029±0.00084 and 3690±250
days, with semi-amplitudes of 3.113±0.224 and 3.056±0.433
m/s and eccentricities 0.08277±0.07509 and 0.17007±0.09428
(see. Table 3 for the full set of parameters). The solution has a
rms=2.39 m/s and a χ2 = 1.30 ± 0.05 per degree of freedom,
showing that the combination of HARPS and UVES data sets
largely improved the parameter uncertainties.
4.3. The planetary system around Gl 433
In the past, Gl 433 was announced as hosting a brown dwarf of
30 Jupiter mass with an orbital period of ∼500 days from astro-
metric measurements Bernstein (1997). But all radial velocity
measurments published after, as the present one, reject this de-
tection.
Apparent Doppler shifts may also originate from stellar sur-
Fig. 2. Top : HARPS radial velocity of Gl 433. Middle : win-
face inhomogeneities, such as plages and spots, which can break
dow function of the measurement. Bottom : Periodogram of the
the balance between light emitted in the red-shifted and the
HARPS measurements.
blue-shifted parts of a rotating star (e.g. Saar & Donahue 1997;
Queloz et al. 2001; Desort et al. 2007). However the large ro-
more precise estimate of this low FAP value, we made use of tation period (>40 days) of Gl 433 ensures that the observed
Cumming (2004) analytic formula : FAP = M.(1 − pmax )(N−3)/2 , doppler shift of 7.37 days does not originate from the stellar
where M is the number of independent frequencies in the peri- activity. A search of correlation between the 7.37 days radial
odogram, pmax its highest power value and N the number of mea- velocity period and Hα , CaII-index or bissector is unsuccess-
surements. We approximated M by 2904/1 (the ratio between the ful in our HARPS data. Such signal is easily detected when
time span of our observations and the typical 1-day sampling), the radial velocity variation is due to activity for a period of
and obtained the very low FAP value of 4 × 10−7 . ∼35 days (and a fortiori for all shorter periods) (Bonfils et al.
We modeled that first periodic signal by a Keplerian orbit. 2007; Forveille et al. 2009, see the case of Gl 176 and Gl 674).
Even though the periodicity was securely identified we used This is a strong evidence that the ∼7 d period is not due to stellar
Yorbit (an heuristic algorithm, mixing standard non-linear min- surface inhomogeneities but to the presence of a planet orbiting
imisations and genetic algorithms; S´ gransan et al. in prep;
e around Gl 433.
Bonfils et al. 2011a) and benefited from a global search without This planet, Gl 433b, belongs to the category of super-Earth
a priori. We converged on a period P = 7.3732 ±0.0023 d, semi- with a minimum mass of ∼5.8 M⊕ . At a separation of 0.058AU
amplitude K1 = 2.99 ± 0.38 m/s and eccentricity e = 0.17 ± 0.13 from its star, Gl 433b is illuminated by a bolometric flux, per
which, for M⋆ = 0.48 M⊙ converts to m sin i = 5.49 ± 0.70 M⊕ surface unity, 10 times higher than what the Earth receives.
4
5. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
Table 2. Fitted orbital solution for the HARPS data of Gl 433
Gl 433b
P [days] 7.373±0.002
e 0.17±0.13
T 0 [JD - 2400000] 54597.0±1.0
ω [deg] 136±47
K1 [m/s] 2.9±0.4
M2 . sin i [M⊕ ] 5.49
a [AU] 0.058
Nmeas 67
S pan [days] 2904
r.m.s [m/s] 2.17
χ2 2.00
Fig. 4. Top : HARPS radial velocity of Gl 667C. Bottom : one
planet plus a linear drift model.
The long period variability detected in the HARPS and
UVES data set may have several origins. The signal can have
as origin a ∼10-year period planet of 50 M⊕ . A possible ori-
gin may also be an effect of a long term stellar magnetic cycle
(like the so-called 11-year solar cycle) during which the frac-
tion of the stellar disk covered by plages varies. In such re-
gion the magnetic field attenuates the convective flux of the
blueshifted plasma and impacts the mean observed radial ve-
locity in the order of few m/s or more (Meunier et al. 2010).
Gomes da Silva et al. (2011) do detect large period variation for
Fig. 3. 2-planets model of HARPS (in red) and UVES (in blue, numerous activity proxy (CaII, NaI, HeI, Hα lines) of Gl 433
from Zechmeister et al. 2009) radial velocity measurements for coherent with a period of ∼10 years. The RV variability at long
Gl 433. Top : phased radial velocity for a planet of 7.37 days period is well correlated with these activity proxies (Gomes da
period. Middle : radial velocity curve for the 3700 day period. Silva et al. in prep). Therefore, we favor a Magnetic Cycle as the
Below : residuals and their periodogram. origin of the long term signal.
5
6. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
Table 3. Fitted orbital solution for the HARPS and UVES data Table 4. 1 planet + 1 linear drift orbital solution for Gl 667
of Gl 433
Gl 667Cb
Gl 433b Gl 433c P [days] 7.1989±0.0015
P [days] 7.3709±0.0008 3693±253 e 0.11±0.07
e 0.08±0.08 0.17±0.09 T 0 [JD - 2400000] 54373.4±0.7
T 0 [JD - 2400000] 54287±1 56740±462 ω [deg] -22.±36.
ω [deg] -156±54 -154±36 K1 [m/s] 3.9±0.3
K1 [m/s] 3.11±0.23 3.1±0.5 M2 . sin i [M⊕ ] 5.69
M2 . sin i [M⊕ ] 5.79 44.6 a [AU] 0.0504
a [AU] 0.058 3.6 γ [km/s] 6.55±0.02
Nmeas 233 γ [m/s/yr]
˙ 1.26±0.18
S pan [days] 4259 r.m.s [m/s] 2.51
r.m.s. [m/s] 2.39 χ2 2.02
χ2 1.30
5. Orbital analysis of Gl 667C Bootstrap randomization indicates FAPs lower than 1/10,000 for
the 4 most powerful peaks whereas Cumming’s prescription at-
We obtained 179 measurements of Gl 667C radial velocity span- tributes them a FAP< 10−12 .
ning 2657 days between June 2004 and September 2011. The To model the RVs with 2 planets + 1 drift, one could pick
data adds 36 points to those analyzed in Bonfils et al. (2011a) the most powerful peak as a guessed period and perform a lo-
and extend their time span by 1070 days. They have uncertainties cal minimization to derive all orbital parameters. We found it is
of ∼1.3 m/s (dominated by photon noise) and both rms and χ2 however not the most appropriate approach here because some
values (resp. 4.3 m/s and 3.04 per degree of freedom) indicate of the less powerful peaks actually correspond to a signal with
a variability above those uncertainties. All RVs are shown as a high eccentricities, and eventually turned to be better fit. To ex-
function of time in Fig. 4 (top panel) whereas their window func- plore the best solutions we generally prefer the global search
tion and floating-mean periodogram are presented Fig. 5 (top implemented in Yorbit with eccentricities left to vary freely. We
two panels). identified several solutions with similar χ2 values, reported in
Table 5. For all solutions, the first planet and the linear drift keep
5.1. A one planet and linear fit solution similar parameter values (see Sect 5.1). On the other hand, the
different solutions are discriminated by different orbital periods
The long-term drift seen in Gl 667C RVs agrees well with the for the second planet, with Pc equals to ∼28, 90, 106, 124, 186
line-of-sight acceleration induced by its companion stellar pair or 372 days.
2
Gl 667AB which is about GMAB /rAB−C ∼ 3m/s/yr (for a to- To understand those signals we look at the periodograms of
tal mass MAB of 1.27M⊙ and a separation of ∼300 AU). Even the residuals around each solution. We found that, on the one
without removing that linear drift the periodogram additionally hand, when the solution is with Pc = 28 d, the periodogram of
shows a peak at P∼7.2 days (see Fig. 5, panel b). We do re- the residual shows the remaining peaks at 91, 105, 122, 185 and
move an adjusted drift (γ = 1.59 ± 0.14 m/s/yr) to make the
˙ 364 days (Fig. 6 - panel a). On the other hand, when the solution
periodic signal even stronger (pmax = 0.53; Fig. 5 panel c). To is with any of the other periods Pc = 90, 106, 124, 186 or 372 d
measure the FAP of the 7.2 days signal we ran 10,000 bootstrap then, only the 28 d peak remains (e.g. Fig. 6 - panels b, c, d, e and
randomization and found no power stronger than 0.18 suggesting f). This means that all peaks at 90, 106, 120, 180 and 364 day
a FAP<< 1/10, 000. We also computed the FAP with (Cumming actually correspond to a single signal, with its harmonics and
2004)’s prescription: FAP = M.(1 − pmax )(N−5)/2 . We approxi- aliases, and that the peak around 28 d is another independent
mate M by 2657/1 (the ratio between the time span and the typ- signal.
ical sampling of our observations) and obtained the extremely One of the 4 signals identified so far (3 periodic signals + 1
low FAP value of ∼ 10−25 . Note that, on Fig. 4 (panel c), a sig- linear drift) have ambiguous solutions. Among the possible pe-
nificant and much less powerful peak is seen around P=1.0094 riods, the ∼106-d period seems to correspond to the rotational
day and corresponds to an alias of the 7.2-day peak with the typ- period of the star as seen in one activity indicator (see. Sect.
ical ∼1 day sampling. 5.3). Conservatively, we continue by assuming that signal is due
We pursued by adjusting with Yorbit the RVs to a model to activity and used the 106-d period to present our fiducial solu-
composed of 1 planet plus a linear drift and converged robustly tion. That assumption is given further credit when we run Yorbit.
on the orbital elements reported in Table. 5. This model reduced Without any a priori on any signal, Yorbit converges on a solu-
the rms and χ2 per degree of freedom to 2.51 m/s and 2.02, tion with P = 7.2, 28 and 106 d. We present the orbital parame-
respectively. They nevertheless remain above the photon noise ters of a 3 planet + 1 drift model in Table 6 and the RV decom-
and instrumental uncertainties, what prompted us to continue the position and periodogram of the residuals around that solution
analysis with the residuals and try more complex models. in Fig 7. That solution has rms and χ2 equal to 1.73 m/s and
1.44±0.06 per degree of freedom, respectively.
5.2. A multi-keplerian plus a linear fit solution Finally, we inspect the residuals around that last model (see
panels (e) and (f) in Fig. 7). We found the power maximum of
Following up on the periodogram of the residuals around the the periodogram located around P = 1.0083 d (a possible 1-day
1 planet + drift model (Fig 5 panel d), we observed additional alias with a period of 121 day) with power pmax = 0.13, to which
power excess around a series of periods, the 6 most power- we attributed a FAP of 2.8%. Therefore, we did not consider that
ful peaks being around 28, 91, 105, 122, 185 and 364 d, with significant sine signal remains in the data. Nevertheless, remain-
p =0.225, 0.215, 0.185, 0.181, 0.134 and 0.123, respectively. ing power excess around the period ∼90 and 122 d suggests the
6
7. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
(a) (b)
(c) (d)
Fig. 5. From the top to the bottom : (a) Window function of the RV measurement; (b)periodograms of the Gl 667C RV measure-
ments; (c) periodograms of the Gl 667C RV measurements after a drift removal; (d) periodograms of the residual after subtraction
of a drift + 1 planet model.
Table 6. 3 planets + 1 linear drift orbital solution our favorite explanation is that the period of ∼105 days and all
the harmonics or alias at P = 90, 124, 186 and 372 days (see
Gl 667Cb Gl 667Cc Gl 667Cd Sect. 5.2) are due to stellar rotation. However, we tried to use
P [days] 7.199±0.001 28.13±0.03 106.4±0.1 different sub-sets of RV points and found that the best solution
e 0.09±0.05 0.34±0.10 0.68±0.06 may appear with Pd = 90, 106 or 186 d. We therefore consider
T 0 [JD - 2400000] 54443.1±0.6 54462±1 54499±1 that the RV signal at large (P > 90) period is not definitively as-
ω [deg] -4±33 166±20 7±8
K1 [m/s] 3.8±0.2 2.0±0.3 2.7±0.4
signed to date, its origin may be stellar rotation (the most proba-
M2 . sin i [M⊕ ] 5.46 4.25 6.93 ble in our point of view), or a high eccentricity planet, 2 planets
a [AU] 0.0504 0.1251 0.3035 in resonnance or a combination of several of these explanations.
γ [km/s] 6.55±0.02 The RV signal at 7.2 and 28.1 d are completely independent
γ [m/s/yr]
˙ 1.85±0.11 of the large period ones and cannot be due to stellar rotation.
r.m.s. [m/s] 1.73 Thus at least 2 super-Earths are present at close separation of
χ2 1.44±0.06 Gl 667C with a mass of 5.5 and 4.25 M⊕ . Already announced by
our team in Bonfils et al. (2011a) with GTO-HARPS data, the
use of supplementary HARPS RV allows us to specify their pa-
rameters. At a separation of 0.05 and 0.12 a.u. from their star,
keplerian fit does not fully account for the signal we attributed
Gl 667Cb and Gl 667Cc are respectively illuminated by a bolo-
to stellar activity.
metric flux, per surface unity, 5.51 and 0.89 times than what
the Earth receives from the Sun (in using stellar luminosity of
5.3. The planetary system around Gl 667C Table 1). The super-Earth Gl 667Cc is then in the middle of the
habitable zone of its star. We discuss this point in detail in the
To assess if one of the radial velocity periodic signal could be next section.
due to stellar rotation we searched for periodicity on several
activity diagnostics (Hα and CaII-index, bisector-inverse slope
(BIS) and full-width at half-maximum (FWHM) of the cross- 6. A planet in the middle of the habitable zone of an
correlation function). The clearest signal detected is a very high M dwarf
peak in the periodogram of the FWHM at a period of ∼105 days
6.1. Gl 667Cc
with a FAP lower than 0.1% (see Fig. 8).
Periodic variation of the FWHM is an estimator of the rota- Super-Earths in the habitable zone of their host stars, which
tion (Queloz et al. 2009). A rotational period of ∼105 days for by definition is the region where liquid water can be stable
Gl 667C is consistent with the faint activity level of these stars, on the surface of a rocky planet (Huang 1959; Kasting et al.
discussed in Sect. 3.2 and such period matches one of the power 1993), currently garner considerable interest. For a detailed dis-
excess seen in our radial velocity periodogram analysis. Thus cussion of the HZ we refer the reader to Selsis et al. (2007)
7
8. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
(a) (b)
(c) (d)
(e) (f)
Fig. 6. Periodograms for the Gl 667C residual of radial velocity measurements after subtraction of a drift plus a 2 planet solution.
For all the panels the period of the first planet is Pb = 7.2 days. From the left to the right and from the top to the bottom the period
of the second planet is Pc = 28, 90, 106, 124, 186 and 372 days.
or Kaltenegger & Sasselov (2011), but we summarize the most the other end of the range, CO2 will irreversibly freeze out from
salient points. One important consideration is that a planets with the atmosphere of planets with T eq < 175K, preventing a suf-
masses outside the 0.5–10M⊕ range cannot host liquid surface ficient greenhouse effect to avoid freezing of all surface water.
water. Planets under the lower end of this range have too weak Either case obviously makes the planet uninhabitable. The inner
a gravity to retain a sufficiently dense atmosphere, and those limit of the habitable zone is well constrained. The outer one, by
above the upper end accrete a massive He-H envelope. In ei- contrast, is very sensitive to the complex and poorly constrained
ther case, the pressure at the surface is incompatible with liquid meteorology of CO2 clouds, through the balance between their
water. The 10M⊕ upper limit is somewhat fuzzy, since planets in reflecting efficiency (which cools the planet) and their green-
the 3–10M⊕ range can have very different densities (reflecting house effect (which warms it) (Forget & Pierrehumbert 1997;
different structure) for a given mass: Earth-like, Neptune-like, Mischna et al. 2000; Selsis et al. 2007). Finally, a location inside
and Ocean planets can all exist for the same mass (e.g. Fig. 3 in the habitable zone is a necessary condition for hosting surface
Winn et al. 2011). water, but by no means a sufficient one: long term survival of
surface water involves complex ingredients such as a carbonate-
To potentially harbor liquid water, a planet with a silicate geological cycle, and an adequate initial H2 O supply.
dense atmosphere like the Earth needs an equilibrium Adopting the notations of Kaltenegger et al. (2011) the equi-
temperature between 175K and 270K (Selsis et al. 2007; librium temperature of a planet is:
Kaltenegger & Sasselov 2011, and references therein). If T eq >
270K, a planet with a water-rich atmosphere will experience a
phase of runaway greenhouse effect (see Selsis et al. 2007). At T eq = ((1 − A)L star /(4βD2 ))1/4 (1)
8
9. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
(a) (b)
(c) (d)
(e) (f)
Fig. 7. Decomposition of our nominal 3 planet + 1 drift model for Gl 667C. (a) panel shows the contribution of the long-term drift
with the 3 Keplerian contribution removed. Panels b, c and d show respectively radial velocity curves for keplerian Pb = 7.2 d,
Pc = 28.1 d and Pd = 106.4 d. Residual of this solution is showed in panel e with their periodogram in panel f.
where β is the geometrical fraction of the planet surface T eq ∼ 270(1 − A)1/4 K, Gl667Cc is therefore in the HZ for any
which re-radiates the absorbed flux (β = 1 for a rapidly ro- albedo in the [0-0.83] range.
tating planet with a dense atmosphere, like the Earth; β = 0.5 Detailed 3-dimensional atmospheric simulations (e.g.
for an atmosphere-less planet that always presents the same Wordsworth et al. 2011; Heng & Vogt 2011) will need to be
side to its star) and A the wavelength-integrated Bond albedo. tuned to the characteristics of Gl 667Cc to ascertain its possible
Using the stellar parameters of Table 1, the equilibrium temper- climate. In the mean time, this planet, which receives from its
ature of Gl433b and Gl667Cb are respectively 495( 1−A )1/4 K and
β star 89% of the bolometric solar flux at Earth, is a very strong
426( 1−A )1/4 K. Both planets are firmly in the hot super-Earth cat-
β
habitable planet candidate.
egory. Gl 667Cc, by contrast, has T eq = 270( 1−A )1/4 K, to be
β
compared to T eq = 278( 1−A )1/4 K for the Earth.
β
6.2. Particularity of the habitable zone around M dwarfs
Two main differences between planets in HZ of solar like stars
Recent 3-D atmospheric models (Heng et al. 2011a,b) sug- and M dwarfs are often pointed out. Firstly, a planet in HZ of
gest that Gl667Cc most likely has β close to 1, even in the case an M dwarf is closer to its star, and therefore subject to more
it is tidally locked and always shows the same hemisphere to intense tidal forces. As a result, it is likely to quickly be cap-
its star, since they find that a modestly dense Earth-like atmo- tured into a spin-orbit resonance. The Solar System demon-
sphere ensures a full re-distribution of the incoming energy. That strates, however, that this does not necessarily imply that it will
conclusion, a fortiori, also applies for the presumably denser be forced into synchronous rotation. The final equilibrium ro-
atmosphere of a 4.25M⊕ planet (Wordsworth et al. 2011). With tation of a tidally influenced planet depends on both its orbital
9
10. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
Table 5. Six commensurable solutions (with similar reduced χ2) for the 2-keplerian orbit + 1 drift model
Pl. P K T0 e
[day] [m/s] BJD−2, 400, 000.0 [day]
b 7.2002±0.0010 4.01±0.26 54443.33±0.53 0.13±0.06
c 28.142±0.031 2.08±0.31 54461.3±1.6 0.32±0.12
γ = 6.547 ± 0.020 km/s
γ˙ = 1.80 ± 0.13 m/s/yr
r.m.s. = 2.15 m/s
χ2 = 1.76 ± 0.05 per degree of freedom
b 7.2002±0.0010 4.19±0.27 54442.89±0.38 0.17±0.06
c 90.24±0.13 2.57±0.61 54483.7±1.3 0.71±0.10
γ = 6.548 ± 0.019 km/s
γ˙ = 1.75 ± 0.13 m/s/yr
r.m.s. = 2.17 m/s
χ2 = 1.77 ± 0.05 per degree of freedom
b 7.2001±0.0010 3.90±0.25 54442.93±0.53 0.13±0.06
c 106.35±0.08 3.30±0.53 54499.46±0.93 0.73±0.06
γ = 6.548 ± 0.019 km/s
γ˙ = 1.63 ± 0.13 m/s/yr
r.m.s. = 2.07 m/s
χ2 = 1.69 ± 0.05 per degree of freedom
b 7.2001±0.0010 3.99±0.27 54442.91±0.45 0.15±0.06
c 123.98±0.14 3.05±0.64 54481.38±0.88 0.80±0.06
γ = 6.550 + −0.019 km/s
γ˙ = 1.77 + −0.13 m/s/yr
r.m.s. = 2.16 m/s
χ2 = 1.71 ± 0.05 per degree of freedom
b 7.2001±0.0010 3.84±0.25 54442.95±0.50 0.14±0.06
c 186.08±0.30 2.79±0.47 54604.4±1.3 0.80±0.05
γ = 6.550 ± 0.018 km/s
γ˙ = 1.75 ± 0.12 m/s/yr
r.m.s. = 2.09 m/s
χ2 = 1.71 ± 0.05 per degree of freedom
b 7.2001±0.0010 3.86±0.25 54442.96±0.49 0.14±0.06
c 372.15±0.57 2.89±0.49 54604.7±1.1 0.87±0.03
γ = 6.550 ± 0.018 km/s
γ˙ = 1.76 ± 0.12 m/s/yr
r.m.s. = 2.09 m/s
χ2 = 1.71 ± 0.05 per degree of freedom
Mercury, for instance, has been captured into the 3:2, rather than
1:1, spin-orbit resonance (Correia & Laskar 2004), and Venus
has altogether escaped capture into a resonance because thermal
atmospheric tides counteract its interior tides (Correia & Laskar
2003). Whatever the final spin-orbit ratio, the tidal forces will
influence the night and day succession, and therefore the cli-
mate. As discussed above however, energy redistribution by an
atmosphere at least as dense as that of the Earth is efficient
(Wordsworth et al. 2011; Heng et al. 2011b,a), and will prevent
glaciation and atmospheric collapse on the night side.
The second major difference is stellar magnetic activity,
through its dependence on stellar mass. M dwarfs, on average,
Fig. 8. Periodograms for the FWHM of the correlation peak are much more active than solar-like star. This results from the
for the Gl 667C HARPS measurements. A clear peak at ∼105 compounding of two effects: lower mass stars have much longer
days is well visible and is interpreted as the rotational period of braking times for stellar rotation (Delfosse et al. 1998; Barnes
Gl 667C. The line show the 10% and 1% FAP level. 2003; Delorme et al. 2011), and for the same rotation period they
are more active (Kiraga & Stepien 2007). As a result, a planet in
HZ of an early M dwarf receives intense X and UV radiation for
eccentricity and the density of its atmosphere (Doyle et al. 1993; 10 times longer than the ∼100 Myrs which the solar system spent
Correia et al. 2008; Correia & Laskar 2010; Heller et al. 2011). close to a very active Sun (Ribas et al. 2005; Selsis et al. 2007).
10
11. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
Stellar X and UV radiation, as well as coronal mass ejections this number to 3 HZ planetary candidates, by discarding 3 plan-
(CMEs), could potentially cause a major planetary atmosphere ets which they find are too hot to host water if their coverage by
escape (see Scalo et al. 2007; Lammer et al. 2009, for reviews). reflective clouds is under 50%. Borucki et al. (2011b) recently
Several theoretical studies have looked into the evolution confirmed Kepler 22b (listed as KOI-87.01 in Borucki et al.
of planetary atmospheres in M-dwarf HZ: do they lose essen- (2011a)) as a planet, making it the first planet with a measured
tial chemical species, like H2 O, and can they even be com- radius orbiting in a habitable zone. Kaltenegger & Sasselov
pletely eroded out? The problem is complex, with many uncer- (2011) however discarded Kepler 22b from their candidate list
tain parameters, and the span of possible the answers is very because its radius is above 2 Earth-radii.
wide. Amongst other uncertain factors, the escape ratio sensi- To summarize, two planets with measured minimum masses
tively depends on: (1) the intensity and frequency of CMEs for in the range for telluric planets (Gl 581d and HD85512b) are
M dwarfs (which is poorly known, and may be much smaller know to orbit in habitable zones. Another one, with a measured
that initialy claimed (van den Oord & Doyle 1997; Wood et al. radius slightly above the nominal limit for a rocky planet, orbits
2005)), (2) the magnetic moment of the planet (a strong magne- in a similar location (Kepler 22b). Finally, 3 KEPLER candidates
tosphere will protect the planet against CME-induced Ion Pick with radii corresponding to telluric planets and positions in hab-
Up (Lammer et al. 2007)), and (3) details of the atmospheric itable zones currently await confirmation. Gl 667Cc, announced
chemistry and composition (through atmosphere-flare photo- in Bonfils et al. (2011a) and discussed in detail here, is actually
chemical interaction (Segura et al. 2010) and IR radiative cool- the most promising of those for holding conditions compatible
ing from vibrational-rotational band (Lammer et al. 2007)). In with surface liquid water. Receiving ∼10% less stellar energy
two limiting cases of planets in M-dwarfs HZ, Lammer et al. than the Earth and with a minimum mass of M2 . sin i = 4.25 M⊕ ,
(2007) conclude that the atmosphere of an unmagnetized Earth- it is very likely to be a rocky planet in the middle of the habitable
mass planet can be completly eroded during the Gyr-long active zone of its star.
phase of its host star, while Tian (2009) find that the atmosphere
of a 7 Earth-mass super-Earth is stable even around very active
M dwarfs, especially if that atmosphere mostly contains CO2 . 7. Summary and conclusions
Continuous outgassing of essential atmospheric species from In this paper we analysed in detail 3 super-Earths announced in
volcanic activity can, of course, also protect an atmosphere by Bonfils et al. (2011a) : Gl 433b, Gl 667Cb and Gl 667Cc. One,
compensating its escape. Gl667Cc, is a M2 . sin i = 4.25 M⊕ planet in the middle of the
These differences imply that a planet in the habitable zone habitable zone of a M1.5V star. It is to date the known extra-
of an M dwarf is unlikely to be a twin of the Earth. Habitability solar planet with characteristics closest to Earth, but does not
however is not restricted to Earth twins, and Barnes et al. (2010) approach being an Earth twin. The main differences from Earth
conclude that “no known phenomenon completely precludes the are a significantly higher mass and a different stellar environ-
habitability of terrestrial planets orbiting cool stars.” A massive ment, which potentially can have caused divergent evolutions.
telluric planet, like Gl667Cc (M2 . sin i = 4.25 M⊕ ), most likely Host stars of giant planets are preferentially metal-rich (e.g.
has a massive planetary core, and as a consequence a stronger Santos et al. 2001, 2004; Fischer & Valenti 2005). The detection
dynamo and a more active volcanism. Both factors help pro- rate of planets with masses under 30-40M⊕, by contrast, does
tect against atmospheric escape, and super-Earths may perhaps not clearly correlate with stellar metallicity (Mayor et al. 2011).
be better candidates for habitability around M dwarfs than true This context makes the discovery of two super-Earths around
Earth-mass planets. Gl 667C ([Fe/H]∼-0.6, Sect. 3) less surprising, but it remains
one of the most metal-poor planetary host known to this date,
6.3. Gl 667Cc compared with the another known planets in with just 6 planetary host stars listed with a lower metallicity in
the habitable zone the Extrasolar Planets Encyclopaedia1 (Schneider et al. 2011).
The metallicity of Gl 433, [Fe/H]∼ -0.2, is close to the median
HARPS has previously discovered two planets inside HZ. value of solar neighbourhood, and therefore unremarkable.
Gl 581d (Udry et al. 2007; Mayor et al. 2009) (M2 . sin i = 7 M⊕ ) Gl 667Cb and c orbit the outer component of a hierarchical
receives from its M3V host star just ∼ 25% of the energy that the triple system. Fewer than 10 other planetary systems, listed in
Earth receives from the Sun, and is thus located in the outer hab- Desidera et al. (2011), share that characteristics. These authors
itable zone of its star. Recent detailed models (Wordsworth et al. conclude that planets occur with similar frequencies around the
2011) confirm that Gl 581d can have surface liquid water for isolated component of a triple system and around single stars.
a wide range of plausible atmospheres. HD85512b (Pepe et al. The planets around Gl 667C, however, are unusual in orbiting
2011) is a M2 . sin i = 3.5 M⊕ planet in the inner habitable zone around the lowest-mass component of the system.
of a K5-dwarf, and receives ∼twice as much stellar energy as The three planets discussed here enter in our Bonfils et al.
the Earth. It can harbor surface liquid water if it is covered by at (2011a) statistical study, which establishes that super-Earths are
least 50% of highly reflective clouds (Kaltenegger et al. 2011). very common around M dwarfs. Our HARPS survey of ∼100
Vogt et al. (2010) announced another super-Earth in the HZ stars has, in particular, found two super-Earths in habitables
of Gl 581, which they found in an analysis combining HARPS zones, Gl 581d and Gl 667Cc, even though both planets are lo-
and HIRES radial velocity data. The statistical significance cated in parts of the mass-period diagram where its detection
of that detection was, however, immediately questioned (e.g. completeness is under 10 percent. This clearly indicates that
Tuomi 2011), and an extended HARPS dataset now demon- super-Earths are common in the habitable zones of M dwarfs,
strates that the planet is unlikely to exist with the proposed pa- with Bonfils et al. (2011a) a 42+54 % frequency. Future instru-
−13
rameters (Forveille et al. 2011). ments optimized for planet searches around M dwarfs, like the
Borucki et al. (2011a) announced 6 planetary candidates in SPIRou (on CFHT) and CARMENES (at Calar Alto observa-
the HZ of Kepler targets with a radius below twice that of tory) near-IR spectrographs, will vastly increase our inventory
Earth, which they adopt as a nominal limit between telluric and
1
Neptune-like planets. Kaltenegger & Sasselov (2011) reduce http://http://exoplanet.eu/index.php
11
12. Delfosse et al.: Super-Earths around Gl 433 and Gl 667C
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