This document provides an overview and context for a study of the symbiotic star SS Leporis using interferometric imaging with the PIONIER instrument on the VLTI. Key points:
- SS Leporis is a long-period interacting binary system composed of an A star accreting material from an evolved M giant companion, presenting an "Algol paradox" where the more evolved star is less massive.
- Previous studies have not fully constrained the system morphology and characteristics. New interferometric observations with PIONIER were obtained to directly probe the inner parts of the system.
- The observations were used to perform aperture synthesis imaging and model the system as a binary surrounded by a circumbinary disc. This provides the
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
Uma grande equipe de astrônomos registrou uma supernova extremamente luminosa numa galáxia massiva a cerca de 3.82 bilhões de anos-luz de distância.
A explosão recém-descoberta, denominada de ASASSN-15Ih, pertence à classe mais luminosa de supernovas, chamada de supernovas superluminosas.
"Ela parece ter originado numa grande galáxia, em contraste com a maioria das supernovas superluminosas, que normalmente se originam em galáxias anãs com formação de estrelas", disse o Dr. Subo Dong, do Kavli Institute for Astronomy and Astrophysics e coautor do artigo publicado na revista Science que descreve a descoberta.
"Nós estimamos o raio efetivo para a galáxia de 7830 anos-luz e uma massa estelar de 200 bilhões de massas solares".
Também conhecida como SN 2015L, a ASASSN-15lh é aproximadamente 200 vezes mais poderosa do que uma típica explosão de supernova do Tipo Ia, cerca de 570 bilhões de vezes mais brilhante do que o nosso Sol, e vinte vezes mais brilhante do que todas as estrelas na nossa galáxia combinadas.
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
Uma grande equipe de astrônomos registrou uma supernova extremamente luminosa numa galáxia massiva a cerca de 3.82 bilhões de anos-luz de distância.
A explosão recém-descoberta, denominada de ASASSN-15Ih, pertence à classe mais luminosa de supernovas, chamada de supernovas superluminosas.
"Ela parece ter originado numa grande galáxia, em contraste com a maioria das supernovas superluminosas, que normalmente se originam em galáxias anãs com formação de estrelas", disse o Dr. Subo Dong, do Kavli Institute for Astronomy and Astrophysics e coautor do artigo publicado na revista Science que descreve a descoberta.
"Nós estimamos o raio efetivo para a galáxia de 7830 anos-luz e uma massa estelar de 200 bilhões de massas solares".
Também conhecida como SN 2015L, a ASASSN-15lh é aproximadamente 200 vezes mais poderosa do que uma típica explosão de supernova do Tipo Ia, cerca de 570 bilhões de vezes mais brilhante do que o nosso Sol, e vinte vezes mais brilhante do que todas as estrelas na nossa galáxia combinadas.
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
Measurements of the_near_nucleus_coma_of_comet_67_p_churyumov_gerasimenko_wit...Sérgio Sacani
Artigo descreve descoberta feita pelo instrumento Alice da sonda Rosetta no cometa 67P/Churyumov-Gerasimenko, das moléculas de água e dióxido de carbono quebradas que pairam pela atmosfera do cometa.
Matter ejections behind the highs and lows of the transitional millisecond pu...Sérgio Sacani
Transitional millisecond pulsars are an emerging class of sources linking low-mass X-ray binaries to millisecond radio pulsars in
binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active
state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray
to optical pulsations are observed only during the high mode. Knowledge of the root reason for this puzzling behaviour remains
elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar
prototype, PSR J1023+0038, covering from radio to X-rays. The campaign was carried out over two nights in June 2021, and involved
12 different telescopes and instruments including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA and FAST.
By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by
changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on
top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with A
The pristine nature of SMSS 1605−1443 revealed by ESPRESSOSérgio Sacani
SMSS J160540.18−144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H] =
−6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C) ≈ 6.1 in the low-C band, as the majority of the stars
in this metallicity range. Yet, constraining the isotopic ratio of key species, such as carbon, sheds light on the properties and origin of these elusive
stars.
Aims. We performed high-resolution observations of SMSS 1605−1443 with the ESPRESSO spectrograph to look for variations in the radial
velocity (vrad) with time. These data have been combined with older MIKE and UVES archival observations to enlarge the temporal baseline. The
12C/
13C isotopic ratio is also studied to explore the possibility of mass transfer from a binary companion.
Methods. A cross-correlation function against a natural template was applied to detect vrad variability and a spectral synthesis technique was used
to derive 12C/
13C in the stellar atmosphere.
Results. We confirm previous indications of binarity in SMSS 1605−1443 and measured a lower limit 12C/
13C > 60 at more than a 3σ confidence
level, proving that this system is chemically unmixed and that no mass transfer from the unseen companion has happened so far. Thus, we confirm
the CEMP-no nature of SMSS 1605−1443 and show that the pristine chemical composition of the cloud from which it formed is currently imprinted
in its stellar atmosphere free of contamination.
EUV fine structure and variability associated with coronal rain revealed by S...Sérgio Sacani
Coronal rain is the most dramatic cooling phenomenon of the solar corona. Recent observations in the visible and UV
spectrum have shown that coronal rain is a pervasive phenomenon in active regions. Its strong link with coronal heating through the
Thermal Non-Equilibrium (TNE) - Thermal Instability (TI) scenario, makes it an essential diagnostic tool for the heating properties.
Another puzzling feature of the solar corona, besides the heating, is its filamentary structure and variability, particularly in the EUV.
Aims. We aim to identify observable features of the TNE-TI scenario underlying coronal rain at small and large spatial scales, to
understand the role it plays in the solar corona.
Methods. We use EUV datasets at unprecedented spatial resolution of ≈ 240 km from the High Resolution Imager (HRI) in the EUV
(HRIEUV) of the Extreme Ultraviolet Imager (EUI) and SPICE on board Solar Orbiter from the spring 2022 perihelion.
Results. EUV absorption features produced by coronal rain are detected at scales as small as 260 km. As the rain falls, heating
and compression is produced immediately downstream, leading to a small EUV brightening accompanying the fall and producing
a ‘fireball’ phenomenon in the solar corona. Just prior to impact, a flash-like EUV brightening downstream of the rain, lasting a
few minutes is observed for the fastest events. For the first time, we detect the atmospheric response to the rain’s impact on the
chromosphere and consists of upward propagating rebound shocks and flows partly reheating the loop. The observed widths of the
rain clumps are 500 ± 200 km. They exhibit a broad velocity distribution of 10 − 150 km s−1
, peaking below 50 km s−1
. Coronal
strands of similar widths are observed along the same loops co-spatial with cool filamentary structure seen with SPICE, which we
interpret as the Condensation Corona Transition Region. Matching with the expected cooling, prior to the rain appearance sequential
loop brightenings are detected in gradually cooler lines from corona to chromospheric temperatures. Despite the large rain showers,
most cannot be detected in AIA 171 in quadrature, indicating that line-of-sight effects play a major role in coronal rain visibility. Still,
AIA 304 and SPICE observations reveal that only a small fraction of the rain can be captured by HRIEUV.
Conclusions. Coronal rain generates EUV structure and variability over a wide range of scales, from coronal loop to the smallest
resolvable scales. This establishes the major role that TNE-TI plays in the observed EUV morphology and variability of the corona.
The extremely high albedo of LTT 9779 b revealed by CHEOPSSérgio Sacani
Optical secondary eclipse measurements of small planets can provide a wealth of information about the reflective properties
of these worlds, but the measurements are particularly challenging to attain because of their relatively shallow depth. If such signals
can be detected and modeled, however, they can provide planetary albedos, thermal characteristics, and information on absorbers in
the upper atmosphere.
Aims. We aim to detect and characterize the optical secondary eclipse of the planet LTT 9779 b using the CHaracterising ExOPlanet
Satellite (CHEOPS) to measure the planetary albedo and search for the signature of atmospheric condensates.
Methods. We observed ten secondary eclipses of the planet with CHEOPS. We carefully analyzed and detrended the light curves using
three independent methods to perform the final astrophysical detrending and eclipse model fitting of the individual and combined light
curves.
Results. Each of our analysis methods yielded statistically similar results, providing a robust detection of the eclipse of LTT 9779 b
with a depth of 115±24 ppm. This surprisingly large depth provides a geometric albedo for the planet of 0.80+0.10
−0.17, consistent with
estimates of radiative-convective models. This value is similar to that of Venus in our own Solar System. When combining the eclipse
from CHEOPS with the measurements from TESS and Spitzer, our global climate models indicate that LTT 9779 b likely has a super
metal-rich atmosphere, with a lower limit of 400× solar being found, and the presence of silicate clouds. The observations also reveal
hints of optical eclipse depth variability, but these have yet to be confirmed.
Conclusions. The results found here in the optical when combined with those in the near-infrared provide the first steps toward
understanding the atmospheric structure and physical processes of ultrahot Neptune worlds that inhabit the Neptune desert.
Confirmation of the_ogle_planet_signature_and_its_characteristics_with_lens_s...Sérgio Sacani
O Telescópio Espacial Hubble e o Observatório W. M. Keck, no Havaí, fizeram confirmações independentes de um exoplaneta orbitando sua estrela central de uma distância bem grande. O planeta foi descoberto através de uma técnica chamada de microlente gravitacional.
Essa descoberta traz uma nova peça para o processo de caçada de exoplanetas: para descobrir planetas longe de suas estrelas, como Júpiter e Saturno estão do Sol. Os resultados obtidos pelo Hubble e pelo Keck apareceram em dois artigos da edição de 30 de Julho de 2015 do The Astrophysical Journal.
A grande maioria dos exoplanetas catalogados são aqueles localizados bem perto de suas estrelas, isso acontece porque as técnicas atuais de se caçar exoplanetas favorecem a descoberta de planetas com curtos períodos orbitais. Mas esse não é o caso da técnica de microlente gravitacional, que pode encontrar planetas mais frios e mais distantes com órbitas de longo período que outros métodos não são capazes de detectar.
Two warm Neptunes transiting HIP 9618 revealed by TESS and CheopsSérgio Sacani
HIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the
star to have two candidate planets with radii of 3.9 ± 0.044 R⊕ (HIP 9618 b) and 3.343 ± 0.039 R⊕ (HIP 9618 c). While the
20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap
in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of
period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d.
High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M⊕ for HIP 9618 b, which,
according to our interior structure models, corresponds to a 6.8 ± 1.4 per cent gas fraction. HIP 9618 c appears to have a lower
mass than HIP 9618 b, with a 3-sigma upper limit of <18M⊕. Follow-up and archival RV measurements also reveal a clear
long-term trend which, when combined with imaging and astrometric information, reveal a low-mass companion (0.08+0.12
−0.05M)
orbiting at 26.0+19.0 −11.0 au. This detection makes HIP 9618 one of only five bright (K < 8 mag) transiting multiplanet systems known
to host a planet with P > 50 d, opening the door for the atmospheric characterization of warm (Teq < 750 K) sub-Neptunes.
Two super-Earths at the edge of the habitable zone of the nearby M dwarf TOI-...Sérgio Sacani
The main scientific goal of TESS is to find planets smaller than Neptune around stars bright enough to allow further characterization studies. Given
our current instrumentation and detection biases, M dwarfs are prime targets to search for small planets that are in (or nearby) the habitable zone
of their host star. Here we use photometric observations and CARMENES radial velocity measurements to validate a pair of transiting planet
candidates found by TESS. The data was fitted simultaneously using a Bayesian MCMC procedure taking into account the stellar variability
present in the photometric and spectroscopic time series. We confirm the planetary origin of the two transiting candidates orbiting around TOI-
2095 (TIC 235678745). The star is a nearby M dwarf (d = 41:90 0:03 pc, Te = 3759 87 K, V = 12:6 mag) with a stellar mass and radius
of M? = 0:44 0:02 M and R? = 0:44 0:02 R, respectively. The planetary system is composed of two transiting planets: TOI-2095b with an
orbital period of Pb = 17:66484 (7 105) days and TOI-2095c with Pc = 28:17232 (14 105) days. Both planets have similar sizes with
Rb = 1:250:07 R and Rc = 1:330:08 R for planet b and c, respectively.We put upper limits on the masses of these objects with Mb < 4:1 M
for the inner and Mc < 7:4 M for the outer planet (95% confidence level). These two planets present equilibrium temperatures in the range of 300
- 350 K and are close to the inner edge of the habitable zone of their star.
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
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
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.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
"Impact of front-end architecture on development cost", Viktor TurskyiFwdays
I have heard many times that architecture is not important for the front-end. Also, many times I have seen how developers implement features on the front-end just following the standard rules for a framework and think that this is enough to successfully launch the project, and then the project fails. How to prevent this and what approach to choose? I have launched dozens of complex projects and during the talk we will analyze which approaches have worked for me and which have not.
Connector Corner: Automate dynamic content and events by pushing a buttonDianaGray10
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The Art of the Pitch: WordPress Relationships and Sales
Eso1148
1. Astronomy & Astrophysics manuscript no. SSLep-final ⃝ ESO 2011
c
November 28, 2011
An incisive look at the symbiotic star SS Leporis⋆
Milli-arcsecond imaging with PIONIER/VLTI
N. Blind1 , H.M.J. Boffin2 , J.-P. Berger2 , J.-B. Le Bouquin1 , A. M´ rand2 , B. Lazareff1 , and G. Zins1
e
1
UJF-Grenoble 1/CNRS-INSU, Institut de Plan´ tologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, France
e
2
European Southern Observatory, Casilla 19001, Santiago 19, Chile
Received xxx / Accepted xxx
ABSTRACT
Context. Determining the mass transfer in a close binary system is of prime importance for understanding its evolution. SS Leporis,
a symbiotic star showing the Algol paradox and presenting clear evidence of ongoing mass transfer, in which the donor has been
thought to fill its Roche lobe, is a target particularly suited to this kind of study.
Aims. Since previous spectroscopic and interferometric observations have not been able to fully constrain the system morphology
and characteristics, we go one step further to determine its orbital parameters, for which we need new interferometric observations
directly probing the inner parts of the system with a much higher number of spatial frequencies.
Methods. We use data obtained at eight different epochs with the VLTI instruments AMBER and PIONIER in the H and K bands.
We performed aperture synthesis imaging to obtain the first model-independent view of this system. We then modelled it as a binary
(whose giant is spatially resolved) that is surrounded by a circumbinary disc.
Results. Combining these interferometric measurements with previous radial velocities, we fully constrain the orbit of the system.
We then determine the mass of each star and significantly revise the mass ratio. The M giant also appears to be almost twice smaller
than previously thought. Additionally, the low spectral resolution of the data allows the flux of both stars and of the dusty disc to be
determined along the H and K bands, and thereby extracting their temperatures.
Conclusions. We find that the M giant actually does not stricto sensus fill its Roche lobe. The mass transfer is more likely to occur
through the accretion of an important part of the giant wind. We finally rise the possibility for an enhanced mass loss from the giant,
and we show that an accretion disc should have formed around the A star.
Key words. Techniques: interferometric - Binaries: symbiotic - Binaries: spectroscopic - Stars: AGB and post-AGB - Stars: funda-
mental parameters - Accretion, accretion disc
1. Introduction erated by shell features that dominate at shorter wavelengths,
while an M star spectrum becomes increasingly obvious at
Symbiotic stars are interacting binaries composed of a hot star longer wavelengths. Welty & Wade (1995) estimated an M4 III
accreting material from a more evolved red giant companion. spectral type for the cool companion, while even earlier types
They are excellent laboratories for studying a wide spectrum of have been estimated by previous authors. The shell is absorb-
poorly understood physical processes, like the late stage of stel- ing light primarily from the A star, indicating some mass loss
lar evolution, the mass loss of red giants, and the mass trans- from the hotter star. The system, however, presents the so-called
fer and accretion in binary systems (Mikołajewska 2007). Their Algol paradox, as the most evolved star is also the least massive,
study has important implications for a wide range of objects, which implies that the cool star must have lost a large quantity
like Type Ia supernovae, barium stars, the shaping of plane- of matter and that the hot companion has accreted part or most
tary nebulae, and compact binaries like cataclysmic variables of it. Moreover, the regular “outbursts” (Struve 1930; Welty &
(Podsiadlowski & Mohamed 2007). Wade 1995) and the UV activity (Polidan & Shore 1993) of the A
SS Leporis (17 Lep; HD 41511; HR 2148) is a prime exam- star shell are clear testimony to ongoing mass-transfer episodes.
ple of such a long-period interacting system, even though it does From interferometric observations, Verhoelst et al. (2007) in-
not belong to the most common symbiotic systems, because the ferred that the mass transfer occurs because the M giant fills its
hot star is not the usual compact white dwarf. As such, SS Lep Roche lobe.
is a symbiotic system in the first phase of mass transfer, while
most symbiotic stars are in their second episode of mass trans-
fer, following the first one that produced the white dwarf. The binary system is additionally surrounded by a large
SS Lep has been known for many decades to present symbi- circumbinary dust disc and/or envelope (Jura et al. 2001).
otic features, and its optical spectrum shows at least three com- Interferometric observations confirmed this fact by revealing its
ponents (Struve & Roach 1939; Molaro et al. 1983; Welty & presence in the inner part of the system (Verhoelst et al. 2011),
Wade 1995). The spectral lines of an A star are largely oblit- further noticing that the structure must be in a disc-like geome-
try to be compatible with the low extinction towards the central
⋆ star. Jura et al. (2001) suggest that the circumbinary disc con-
Based on observations made with the VLTI European Southern
Observatory telescopes obtained from the ESO/ST-ECF Science tains large grains that are formed by coagulation and, based on
Archive Facility. the large and rather unique 12 µm excess of SS Lep despite its
1
Article published by EDP Sciences, to be cited as http://dx.doi.org/10.1051/0004-6361/201118036
2. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
Table 1. Previously estimated parameters of SS Lep Table 2. VLTI Observation log of SS Lep for the AMBER and
PIONIER observations.
System A star M star
d [pc] 279 ± 24 a SpT A1V b M6III c Run Date Baselines Range
P [d] 260.3 ± 1.8 b T eff [K] 9000 c,d 3500 c,d A1 11-11-2008 E0-G0-H0 15 - 130 m
e 0.024 ± 0.005 b θ [mas] 0.53 ± 0.02 c 3.11 ± 0.32 c 13-11-2008 A0-G1-K0
i 30◦ ± 10◦ c R [R⊙ ] ∼15 c 110 ± 30 c A2 26-12-2008 A0-G1-K0 90 - 130 m
f (M) 0.261 ± 0.005 b F [%] 11 ± 7 c 60 ± 50 c A3 21-02-2009 D0-G1-H0 15 - 75 m
1/q 4 ± 1 b,c M [M⊙ ] 2∼3 a,b 0.4∼1 a,b 28-02-2009 E0-G0-H0
A4 07-04-2009 D0-G1-H0 65 - 70 m
Notes. d is the distance, P the orbital period, e the eccentricity, i the P1 28-10-2010 D0-G1-H0-I1 15 - 80 m
inclination, f (M) the mass function, q = M M /MA the mass ratio. For 30-10-2010 D0-E0-H0-I1
the stars, SpT is the spectral type, T eff the temperature, θ the apparent P2 29-11-2010 E0-G0-H0-I1 15 - 70 m
diameter, R the linear radius, F the flux contribution at 2.2 µm, and M P3 07-12-2010 D0-G1-H0-I1 45 - 80 m
the mass. References: (a) Van Leeuwen 2007; (b) Welty & Wade 1995; P4 22-12-2010 A0-G1-K0-I1 45 - 130 m
(c) Verhoelst et al. 2007; (d) Blondel et al. 1993.
valuable information without biasing the results, more specif-
rather low luminosity, that the disc may be losing mass by a wind ically the estimation of the binary orientation. Typical (u,v)-
at a rate of 8 × 10−9 M⊙ yr−1 . planes for AMBER and PIONIER observations can be seen in
The orbital characteristics and circumbinary disc of SS Lep Fig. 1.
very closely resemble those of the post-AGB binaries with sta-
ble, Keplerian circumbinary dust discs (van Winckel 2003), and,
as such, SS Lep may be considered as a system linking binary M AMBER data We used archive AMBER data obtained during
giants and post-AGB systems – the M-giant should indeed very four different nights in a period of 200 days (more than half an
soon evolve into a post-AGB star. In those post-AGB binaries, orbital period). They cover simultaneoulsy the J-, H-, and K-
the spectra are rich in crystalline features while the spectrum bands with a spectral resolution R ∼ 35. Even though J-band
of SS Lep appears entirely amorphous, which, if a link is in- fringes have been properly recorded in several observations, we
deed in order, would imply further dust processing in the disc. decided to discard them from the analysis of this paper since the
Whether the disc can survive long enough if it is indeed losing data quality is significantly worse than for longer wavelengths.
mass through a wind is, however, still an open question. Raw visibility and closure phase values were computed using the
Cowley (1967) argued that the system consists of a B9 V latest public version of the amdlib package (version 3; Malbet
primary and an M1 III secondary in a 260-d eccentric orbit et al. 2010) and the yorick interface provided by the Jean-Marie
(e = 0.132). She developed a scenario in which the secondary Mariotti Center.
fills its Roche lobe near periastron and mass transfer proceeds
for a short time thereafter. From spectra covering 3.5 orbits, PIONIER data They were obtained in the H-band between the
Welty & Wade (1995) proved this scenario unlikely, as their re- end of October 2010 and December 2010 during the commis-
vised orbit provided a similar orbital period but a significantly sioning runs of the instrument. We used the prism that provides
reduced eccentricity e = 0.024. They estimated a mass ratio of a spectral resolution R ∼ 40, that is, six spectral channels
1/q = 3.50 ± 0.57, where the error was very likely severely un- across the H-band. Because these observations have been made
derestimated given the poor fit of the single Mg II line they used during the commissioning (less than four hours of observation
to measure the radial velocity of the A star. for each night), the (u,v)-plane coverage is still relatively poor
Recently, Van Leeuwen (2007) has reevaluated the parallax compared with a whole night of observations but more complete
of SS Lep from Hipparcos data, obtaining π = 3.59 ± 0.31 mas, than AMBER’s. Data were reduced with the pndrs package
that is, a distance of 279 ± 24 pc, so smaller than the previously presented by Le Bouquin et al. (2011).
and generally used value of 330+90 pc. The most recent parame-
−60
ters of SS Lep, as collected from the literature until the present The low spectral resolution multiplies the number of spatial
work, is presented in Table 1. frequencies, and brings a wealth of information (Sect. 4). This is
We report here interferometric observations that have al- especially true with AMBER for which the (u,v)-coverages were
lowed model-independent image synthesis (Section 3) and a relatively poor.
more precise modelling of the system (Section 4). Section 5 fo-
cuses on the binary by determining mainly the orbital parame-
ters and the M star diameter. We finally discuss the mass transfer
process in Section 6. 50 50
V [106 rad−1]
V [106 rad−1]
2. Observations 0 0
Data were collected at the Very Large Telescope Interferometer
(VLTI; Haguenauer et al. 2010) with the spectrograph AMBER −50 −50
(Petrov et al. 2007) and the four-telescope visitor instrument
PIONIER (Le Bouquin et al. 2011). All observations made use −50 0 50 −50 0 50
of the 1.8-m Auxiliary Telescopes. Table 2 presents the observa- U [106 rad−1] U [106 rad−1]
tion log. Three data sets are the combination of two observations
separated in time by a few days (seven to the maximum) to in- Fig. 1. Typical (u,v)-plane coverage for AMBER (left, November 2008)
crease the (u,v)-plane coverage. We made sure that this brings and PIONIER (right, October 2010) observations.
2
3. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
28−10−2010 07−12−2010 22−12−2010
5
A star
N (mas) −−−>
M giant
0
−5
−5 0 5 −5 0 5 −5 0 5
E (mas) −−−> E (mas) −−−> E (mas) −−−>
Fig. 2. Model-independent image reconstruction of SS Lep obtained during the PIONIER runs P1, P2, and P4. The resolved M giant and the A
star are clearly identified. The images are centered on the center of mass (central cross) as determined from Section 5.2. The distortion of the giant
in the image is most certainly due to an asymmetric PSF rather than to a definite tidal effect. Three faint artefacts are visible on the periphery of
the image.
3. Image synthesis i.e. less than seen in the image. Additionally, its orientation in
the image corresponds well with the asymmetry observed in the
With its four telescopes, PIONIER provides six visibilities and corresponding (u, v)-planes. It was actually not possible to im-
four closure phases simultaneously, which allows a reliable im- age the circumbinary disc because of the lack of data with short
age reconstruction for the four observations. We used the MIRA baselines.
software from Thi´ baut (2008). MIRA proceeds by direct min-
e
imisation of a penalised likelihood. This penalty is the sum of
two terms: a likelihood term that enforces agreement of the 4. Modelling
model with the data (visibilities and closure phases), plus a reg-
ularisation term to account for priors. The priors are required to Our observations clearly show that SS Lep is a spatially resolved
lever the possible degeneracies due to the sparseness of the spa- binary whose M giant is actually resolved for all observations.
tial frequency sampling. We use here the “total variation” regu- We built a geometrical model to determine the characteristics of
larisation associated with positivity constraint as recommended the individual components. The M giant and the A star are mod-
by Renard et al. (2011). The pixel scale is 0.25 mas and the field- elled as uniform discs, and the circumbinary material is mod-
of-view is 200×200 pixels. The starting point is a Dirac function elled as a Gaussian envelope. We tried to detect a possible tidal
in (0, 0). We set the hyper-parameter to a low value of 100, so distortion of the giant or matter escaping from its atmosphere by
that the weight of the regularisation term is kept small with re- modelling it with an elongated uniform disc. Results were not
spect to the fit to the data. It brings some super-resolution, at the persuasive and, similar to the image reconstruction, we cannot
cost of an improved noise level in the image. We combined all conclude anything about this because we lack the longest base-
the spectral channels to improve the (u, v)-plane coverage. That lines able to measure distortion of a few percent. The spatial
the image is indeed “grey” over the H-band is demonstrated in resolution of 1 mas was also not sufficient to resolve the putative
the next section. The reconstructed images for runs P1, P2, and shell or an accretion disc around the A star, which agrees with
P4 are presented in Fig. 2. Each image shows the binary nature of the 0.5 mas size estimated from the spectral energy distribution
SS Lep, the separation being slightly smaller than 5 mas. From (SED) in Verhoelst et al. (2007). We therefore fixed its diameter
one observation to the next, we can observe the rotation of the to 0.5 mas.
system. The model we used to fit the interferometric data (visibilities
The A star and its shell have an expected spatial extension and closure phases) therefore comprises six degrees of freedom:
of 0.5 mas (Verhoelst et al. 2007) so that we do not expect to the relative flux contribution of two components of the system,
resolve them with our VLTI baselines. Therefore, the size of the the binary separation and its orientation, the size of the M giant,
spot corresponding to the A star more or less defines the point the size of the circumbinary envelope. Our data sets are perfectly
spread function (PSF) of the image, about 1 mas large. Because suited to spectral analysis. To properly fit the data it appeared
the M giant is the most luminous component of the system in necessary to consider the fluxes to be wavelength-dependent.
the H-band, we identify it in the image as the darkest spot. With The data and the results of our fits are presented in the
respect to the A star, we clearly see that it is spatially resolved Appendix. Starting from the PIONIER images, we are able to
and measures approximately 2 mas in diameter. We expect the measure the binary separation and orientation for each dataset
distortion observed in the image to come from an asymmetric independently. The relative flux of the three components could
filling of the (u, v)-plane (implying a non-circular PSF on the be recovered between 1.6 and 2.5 µm, with a dispersion of 3%
reconstructed image) rather than to a real tidal distortion. As a between the different epochs. The relative flux ratios are al-
matter of fact, the tidal distortion would be around 5 ∼ 7%, most constant over the H-band, which validates the “grey” ap-
3
4. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
Table 3. Orbital parameters of SS Lep obtained by combining previous
radial velocities (Welty & Wade 1995) with our 8 astrometric measure-
ments.
Semi major axis a 4.492 ± 0.014 mas
Linear semi major axis a 1.26 ± 0.06 AU
Inclination i 143.7 ± 0.5◦
Eccentricity e 0.005 ± 0.003
Longitude of the ascending node Ω 162.2 ± 0.7◦
Argument of periastron ω 118 ± 30◦
a quasi-circularised orbit observed with an inclination angle be-
tween 28◦ and 38◦ . The circularised orbit is not a surprise for an
evolved symbiotic system, with an M giant in a short orbit. For
instance, Fekel et al. (2007) find that 17 of the 21 (i.e. 81%)
red symbiotic systems with periods P ≤ 800 days have circular
orbits.
This result definitely invalidates the periastron-passage mass
transfer scenario of Cowley (1967), which required a significant
Fig. 3. SS Lep best orbit (dashed line) obtained by combining previ- eccentricity (e = 0.134) to explain the regular “outbursts” of
ous radial velocities (Welty & Wade 1995) with our astrometric mea- the system. Finally, given the almost null eccentricity, ω is also
surements. The central dot indicates the A star. AMBER and PIONIER poorly constrained.
points are respectively presented by the red and blue crosses represent-
ing the 3-σ error bars. The corresponding points on the best orbit are
indicated by the short segments originating in each point. 5.2. The masses
Combining our value for the inclination with the binary mass
proach used in Sect. 3. We tried to measure a chromatic diam- function obtained by Welty & Wade (1995), we can estimate
eter for the giant but results were not consistent between the the individual mass of the stars, hence the mass ratio. The main
different epochs. Finally, despite the relatively long period be- source of uncertainty in this estimation resides in the distance,
tween AMBER and PIONIER observations (almost two orbital as determined by Hipparcos. Using the distance and the angu-
periods), we note rather good consistency of results within error lar separation of the two stars, we obtain a = 1.26 ± 0.06 AU,
bars, indicating that the system is relatively stable. and thus, through Kepler’s third law, the total mass of the sys-
We were not able to extract much information about the large tem is estimated as 4.01 ± 0.60 M⊙ . We then derive MA =
circumbinary disc because of the lack of very short baselines. 2.71 ± 0.27 M⊙ , M M = 1.30 ± 0.33 M⊙ , and 1/q = MA /M M =
The disc is almost totally resolved with the smallest projected 2.17 ± 0.35. The mass ratio is thus much greater than previously
baselines of 15 m. We were only able to roughly determine its thought. While the A star still has a mass in the range 2 − 3 M⊙ ,
full width at half maximum (FWHM) for only two observations the mass of the M giant is now much higher than estimated ear-
out of eight (A1 and A4), and its relative flux for 6 of them (A1, lier, and this implies that less matter was transferred into the
A3, P1 to P4). We measured an FWHM of 12.2 ± 0.2 mas in system than previously guessed. We come back to this later.
agreement with the estimation of Verhoelst et al. (2007) in the
near-IR. The disc has been observed in the mid-IR by Verhoelst 5.3. The M star
et al. (2011), who measured a Gaussian FWHM of 26 mas.
Obervations with the 10-metre baselines of the Keck Segment- Averaging over all the epochs, we measure an apparent diameter
Tilting Experiment at 10.7 µm did not resolve it (Monnier et al. for the M star θ M,UD = 2.208 ± 0.012 mas, where the error is
2009) and indicate that it should not be larger than 200 mas in computed from the dispersion of the eight estimations. The er-
the mid-IR. ror bars do not include systematic effects like, for instance, tidal
distortions, which could increase error bars by a few percent. It
was also not possible to identify a dependence in the giant size
5. Characteristics of the individual components as a function of the wavelength. The previous VINCI observa-
5.1. The orbit of SS Lep tions of Verhoelst et al. led to a higher value of 2.94 ± 0.3 mas,
most likely because theirs was the result of a one-year survey of
To compute the most reliable orbit possible, we combined our the source, without any phase information in the interferometric
eight astrometric positions of the binary with the radial veloc- data. This involved modelling the system as a symmetric object,
ities of the M star obtained by Welty & Wade (1995)1 . We so that it was impossible to disentangle the signatures of the ro-
deduced the orbital parameters from a global χ2 minimisation tating binary from the resolved giant one.
of these data. The best-fit orbit is shown in Fig. 3, and the or- The conversion factor from the uniform disc to a limb-
bital parameters are listed in Table 3. Uncertainties on the or- darkened one differs by a few percent depending on the authors3 .
bital elements are estimated via Monte-Carlo simulations. The We adopt a value of 1.04, which leads to a limb-darkened diam-
inclination angle of 143.7◦ and the non-significant eccentricity2 eter equal to θ M,LD = 2.296±0.013 mas. These results agree with
confirm the previous measurements of Welty & Wade (1995) of
3
Verhoelst et al. calculate a factor of 1.058. Using the results of
1
We discarded the A star radial velocitites that were not convincing. Hanbury Brown et al. (1974) and Claret (2000), we find a conversion
2
The astrometric points alone lead to an eccentricity of 0.004±0.008, factor of 1.044, and with the method of Davis et al. (2000), it is equal
compatible with a circular orbit. to 1.030 (van Belle et al. 2009).
4
5. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
5
Table 4. Stellar parameters extracted in this study.
M star A star
2
Mass [M⊙ ] 1.30 ± 0.33 2.71 ± 0.27
Apparent diameter [mas] 2.208 ± 0.012 0.6 ± 0.05
Linear radius [R⊙ ] 66.7 ± 3.3 ∼ 18
Temperature [K] 3500 ± 200 ∼ 9000
λ Fλ [W.m−2]
10−10
5 pendencies are the temperature and the metallicity (Gustafsson
et al. 2008). The A star is in the Rayleigh-Jeans regime: it is
impossible to fit simultaneously its temperature and size. We
leave its diameter free and model its SED by a KURUCZ model
2 at 9000 K (Castelli & Kurucz 2003). The disc is modelled by
a Gaussian whose FWHM and blackbody temperature are left
free. We use the absorption law of Cardelli et al. (1989) with
10−11
1.6 1.8 2.0 2.2 2.4
RV = 3.1 and AV = 0.7 mag (Verhoelst et al. 2007; Malfait,
Bogaert, & Waelkens 1998). Additionally, we force the total
λ [microns] SED (M giant + A star + disc) to be compatible with the 2MASS
measurements (Skrutskie et al. 2006). The lack of an absolute
Fig. 4. Flux of the M giant (red), the A star (blue), and the envelope spectrum makes difficult a more realistic modelling. The best fit
(magenta). The grey curve is the M star MARCS spectrum. In black is is presented in Fig. 4. Our estimation of the stellar parameters
the sum of the three components adjusted to the 2MASS magnitudes in
are summarised in Table 4.
the H- and K-bands. The dots are the data plus the error bars, and the
solid lines are the models for each of the components. The M star temperature is found to be around 3500 ± 200 K.
We also confirm that the A star is apparently larger than expected
from its spectral class (θA = 0.6 ± 0.05 mas, or a linear radius of
about 18 R⊙ ). For the disc, we found a blackbody temperature
the limb-darkened diameter estimated from the SED of Verhoelst
of 1700 ± 100 K and an FWHM of 8.0 ± 0.5 mas. Interestingly,
et al. (θ M,LD = 2.66 ± 0.33 mas). Taking the uncertainty on the
this is incompatible with the 12 mas derived from the fit of vis-
distance into account, the M giant radius is R M = 66.7 ± 3.3 R⊙ ,
ibility curves in Sect. 4. We see this inconsistency as a hint that
which is 40% smaller than previously obtained. This leads to a
a Gaussian geometry is probably too simple to model the cir-
surface gravity log g ∼ 0.9.
cumbinary environment.
Dumm & Schild (1998) provide measurements of radius for
(non-Mira) M star, showing that with a radius around ∼ 65 R⊙ ,
the M star spectral type should be M1/M2. Given the orbital pe- 6. The mass transfer process
riod, M¨ rset & Schmid (1999) agree by deriving a spectral type
u
between M0 and M1. From the table of these authors, stars with As explained above, SS Lep shows evidence of mass transfer be-
similar luminosities to the one estimated for the M giant of SS tween the M giant and the A star, and this mass transfer is not
Lep all have a radius between 42 and 67 R⊙ . completely conservative. We now revisit the possible physical
Based on the dependence of the nuclear time scale on stel- foundations for this mass transfer according to the new parame-
lar mass, the M star must have an initial mass at least 20% ters of the system derived in previous sections.
higher than its companion to have evolved on the AGB, while The observations suggest that the mass transfer is driven by
its companion is still in the phase of central hydrogen burn- a wind-Roche Lobe overflow (wind RLOF; Podsiadlowski &
ing. Because the initial mass of the system was probably greater Mohamed 2007). We indeed show here that the current state of
than its current value, this implies an initial mass of the giant the system seems to require an enhanced mass loss from the gi-
M M,0 > 2.2 M⊙ 4 . Finally, stars with such masses (unless much ant and that this wind possibly fills the Roche lobe and makes the
larger) never go through a stage with large radii when on the mass transfer almost conservative. We also show that it is quite
RGB – with the maximum radius reached of the order of 30 R⊙ possible that an accretion disc formed around the A star, which
– which indicates the M star is more likely on the early-AGB may explain its abnormal luminosity.
phase.
6.1. Mass transfer by Roche Lobe overflow from the wind
5.4. Temperature of individual components Our results indicate that the M giant only fills around 85 ± 3% of
The modelling presented in Sect. 4 allows us to estimate the its Roche lobe (Fig. 5). This contradicts the results of Verhoelst
relative flux of the three components between 1.6 and 2.3 µm et al. (2007) . The reasons of this difference are threefold.
(see Appendix). These measurements can be used to constrain
the temperature and the size of the individual components. We 1. Our more precise interferometric measurements led us to es-
impose that the M giant diameter is 2.2 mas as estimated pre- timate a smaller giant radius than in previous studies.
viously. We model its SED with a MARCS model whose de- 2. The revised HIPPARCOS distance brings the system closer
than previously thought. This makes the stars smaller, while
4
Since we expect the M star to have had an initial mass at least the orbital radius is mostly given by the orbital period and is
20% higher than the A one q0 = M M,0 /MA,0 > 1.2, and therefore almost independent of the distance.
M M,0 + MA,0 > 1.85M M,0 . Finally, because the system was most likely 3. We have determined for the first time the mass ratio and find
more massive initially, we get 1.85M M,0 > MA + M M , that is, M M,0 > a higher value than previously guessed. This leads to a higher
0.55(M M + MA ) ≃ 2.2 M⊙ . mass and Roche lobe radius of the giant.
5
6. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
Our results disprove a stricto sensus current RLOF. Two mech-
anisms might occur that leave this possibility open however, but
they can be discarded with quantitative arguments. Α
First, radiation pressure reduces the gravitational accelera- Μ
tion influence, so that the Roche potential surface shrinks
(Schuerman 1972). Dermine et al. (2009) estimated the ratio of
the radiation to the gravitational force to be f ∼ 10−2 to 10−1 for
the M giant of SS Lep. It reduces the Roche lobe radius by only Fig. 5. Representation of the modified Roche equipotential (solid line)
1 to 4%. For the giant to fill its Roche lobe we need f = 0.35, for a mass ratio 1/q = 2.2. The limb-darkened diameter of the M giant
which implies that the L1 and L2 points share the same equipo- is the dashed line, while the A star one is the dark dot.
tentials, making it more difficult for the A star to accrete, most
of the matter finally going into the circumbinary disc. However,
the mass of the latter is rather low according to Jura et al. (2001) whereas we expect it to have lost at least 0.9 M⊙ . As the M star is
(Mdust ∼ 2 × 10−5 M⊙ ), so that this is unlikely. on the AGB since only a few million years – and will stay there
Second, atmosphere stratification in red giants indicates that for a few million years more at most – it cannot have lost much
there is no single radius value, and it may be not obvious what mass since then.
really fills the Roche lobe. Pastetter & Ritter (1989) have shown There is, however, some evidence of enhanced wind mass
that for very evolved stars the scale height of the density stratifi- loss of giants in binaries compared to single giants of the same
cation in their atmosphere is a significant fraction of their photo- spectral type (Mikołajewska 2007; Jorissen 2003). From a the-
spheric radius, so that mass flows through the inner Lagrangian oretical point of view, the presence of a companion reduces
point L1 long before the photosphere reaches the critical Roche the effective gravity of the mass-losing star, thus enhancing the
equipotential. Because it is on the early AGB phase, the M giant mass loss. In the case of SS Lep, the so-called CRAP mecha-
in SS Lep is still very far from these evolutionary stages, so that nism of tidally enhanced stellar wind (Tout & Eggleton 1988)
this effect is negligible here. allows a mass loss rate 150 times higher than the Reimers rate5 ,
i.e. ∼ 2.4 × 10−6 M⊙ yr−1 . Soker, Rappaport, & Harpaz (1998)
Finally, to discard the RLOF mechanism, we should explain and Frankowski & Tylenda (2001) have also shown that, in this
the 0.0126 mag ellipsoidal variablility in the visible from Koen case, the mass loss is strongly enhanced in the equatorial plane,
& Eyer (2002). This variability can be interpreted as the signa- while an accretion disc can form during wind accretion (Theuns,
ture of a distorted photosphere, whose flux in the line of sight Boffin,& Jorissen 1996; Nagae et al. 2004).
varies periodically. In the present case, it would correspond to a To validate our scenario of a wind RLOF and of enhanced
change in radius of about 8-9 %. However, given the low incli- mass loss by wind from the giant, we have considered the pos-
nation of the system, even if the star was filling its Roche lobe, sible evolution of a binary system, taking the CRAP mechanism
it would not show such a large variation in radius. Moreover, the into account, and following the methodology of Hurley,Tout, &
data in the K-band of Kamath & Ashok (1999), where the M Pols (2002).We start with a system having an initial period of
giant dominates, are hardly convincing evidence of any periodic 160 days and initial masses MM,0 = 2.28 M⊙ , MA,0 = 1.85 M⊙ .
variations in SS Lep. The Hipparcos variability must thus have For about 1 Gyr, the system evolves without much change, and
another origin than a tidal distortion of the M giant. If the reason the primary star starts its ascent of the AGB. After 2.8 Myr, the
for the light variation in the visible is the primary source of light masses and period have reached the currently observed values,
in the system, a change of less than 0.6% is required to explain with about 0.1 M⊙ having been lost by the system, and form-
the observed amplitude. The cause of this change is, however, ing some circumbinary disc. The mass loss and transfer oc-
not known. curred mostly during the last 500 000 years, with a mass loss
We therefore conclude that an RLOF is unlikely in SS Lep. ∼ 10−6 M⊙ yr−1 . During the whole process, the Roche lobe ra-
Podsiadlowski & Mohamed (2007) suggest the possibility of a dius around the M star remained similar, the lowest value being
new mode of mass transfer – the wind Roche lobe overflow – 74 R⊙ . No RLOF should thus have happened, unless the initial
where a slow wind fills the Roche lobe (e.g. Mira stars in symbi- eccentricity was very high.
otic systems). Because the wind speed in M giants is rather small The above scenario is certainly not the only possible one, but
(around 10 ∼ 15 km s−1 ) and lower than the orbital one for SS it shows that we can explain the current and peculiar properties
Lep (vorb = 48 km s−1 ), we expect it to be in the particular case of of SS Lep (including a low-mass circumbinary disc), without
a wind Roche lobe overflow, where a substantial part of the stel- resorting to an RLOF and with a low mass loss rate of the order
lar wind can be accreted. The simulations of Nagae et al. (2004) of 10−6 M⊙ yr−1 .
show that at least 10% of the M giant wind could be accreted in
SS Lep.
6.3. Accretion on the A star
6.2. Need for enhanced mass loss from the M giant From the previous sections, the accretion efficiency is ex-
pected to be much higher than 10% in SS Lep, perhaps in the
As seen in the previous section, the mass transfer in SS Lep range of 80-90%, while the mass loss rate could reach around
is likely due to high-efficiency accretion of the M giant stel- 10−6 M⊙ yr−1 . This corresponds to an accretion rate of a few
lar wind. However, it is difficult to explain the current system 10−7 ∼ 10−6 M⊙ yr−1 on the A star. This agrees with the 3.3 ∼
state with normal stellar wind rates, which are too low. Indeed, 5.5 × 10−7 M⊙ yr−1 of Blondel et al. (1993), when interpreting
before the AGB phase, the typical mass loss rates are around
∼1-2 × 10−8 M⊙ yr−1 at the normal (e.g. Reimers) rate. The M 5
Because the M star fills more than 50% of its Roche lobe, we con-
giant (with an expected initial mass > 2.2 M⊙ ) should have lost sider an enhancement factor 1 + B/26 = 156, where B ∼ 104 , as de-
only a few hundredths of a solar mass before reaching the AGB, scribed by Tout & Eggleton (1988).
6
7. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
the Lyman-α emission in terms of the recombination of H+ dur- It is likely that for a short time, the system will appear as a non-
ing the inflow of matter. spherical planetary nebula, where the asymmetry is due to the
Verhoelst et al. (2007) propose that the A star could have circumbinary material. The A star will have its mass increased
“puffed up” by factors of five to seven because of too fast ac- to 3.3 M⊙ . Because the primary will not have time to go through
cretion in order to explain its abnormal luminosity. The calcu- the thermal pulses phase, it will most likely not be polluted in
lations of Kippenhahn & Meyer-Hofmeister (1977) require an s-process elements. The period will have increased to 900 days,
accretion rate of 5 × 10−5 M⊙ yr−1 to reconcile the luminosity and so the system will appear in the typical location in the (e − log P)
the spectral type for an increase in diameter of a factor of ten 6 . diagram for post-mass transfer systems (Boffin, Cerf, & Paulus
This is too high compared to the value we derived previously. 1993). When in the post-AGB phase, the system will thus appear
Moreover, in this scenario a shell spectrum is hiding the A star typical of those discovered, with a circumbinary disc and an or-
spectrum so that a clear determination of the stellar parameters bital period between 200 and 1800 days (van Winckel 2003). The
is prevented; in particular, the gravity of the star cannot be es- A star will then undergo its evolution as a red giant and the sys-
timated accurately. If we make the reasonable assumption that tem will most likely again be a symbiotic system – more usual
the A star is rotating in the orbital plane, based on the measured this time, given the presence of a white dwarf.
v sin i = 118 km s−1 (Royer et al. 2002), we derive an equato-
rial velocity of 196 km s−1 . It is above the break-up speed for a
2.7 M⊙ star with a radius of 18 R⊙ , which is 170 km s−1 . These 7. Conclusion and future work
arguments challenge the “puffed up” scenario, so we can wonder We have presented here the results of VLTI observations, and we
if the A star indeed has such a large radius. focused on the binary. After having computed the characteristics
Another explanation for the abnormal luminosity of the A of the orbit, we demonstrated that the mass ratio is lower than
star could be the presence of an accretion disc. Indeed, the Ly-α previously thought and that the M giant does not fill its Roche
emission profile observed by Blondel et al. (1993) consists of a lobe. However the system is possibly in the configuration of a
single, asymmetric and redshifted feature, suggesting a signif- wind Roche lobe overflow, where a substantial part of the gi-
icant absorption by the extended atmosphere in the equatorial ant’s stellar wind can be accreted by the A star. We also have
plane. This could be a hint of wind RLOF presenting a focused good reasons to think that the A star is actually surrounded by
wind in the equatorial plane and of the presence of an accretion an accretion disc, although this needs to be investigated further.
disc. This disc would easily explain the shell nature of SS Lep as We still lack a low-resolution spectro-photometry of SS Lep
well as the variability of its spectrum. This accretion disc is also between 1.6 and 2.5 µm to compute the absolute luminosity of
expected from a mechanical point of view in the wind RLOF each component and extract more specific information. The cur-
scenario because most of the matter goes through the L1 point. rent data also present good hints of unmodelled material escap-
The matter will fall towards the A star and, because of its initial ing the system. It would be of uttermost importance to obtain
angular momentum, it will reach a minimum radius of additional interferometric observations of SS Lep – at large but
rmin also small baselines – to study the binary interactions in more
= 0.0488 q−0.464 , details (M star distortion, mass transfer, circumbinary disc) and
a
to determine if the A star is surrounded by an accretion disc.
before forming an accretion disc. In the present case, this
amounts to 20 R⊙ , larger than the star (even if it has expanded). Acknowledgements. The authors would like to thank O. Absil and G. Dubus
Moreover, at the beginning of the mass transfer, rmin ≃ 9 R⊙ , for their help, as well as the referee N. Elias, whose careful review of the text
which is also larger than the radius of an A star on the main se- helped them improve the papers clarity and quality. PIONIER is funded by
quence (∼ 2-3 R⊙ ). It is thus likely that a disc has formed. The the Universit´ Joseph Fourier (UJF, Grenoble) with the programme TUNES-
e
SMING, the Institut de Plan´ tologie et d’Astrophysique de Grenoble (IPAG,
e
radius of this disc would be about ex-LAOG), and the Institut National des Science de l’Univers (INSU) with
rcirc the programmes “Programme National de Physique Stellaire” and “Programme
= 0.0859 q−0.426 , National de Plan´ tologie”. PIONIER is equipped with a detector provided by W.
e
a Traub (JPL, Caltech). The authors want to warmly thank the VLTI team. This
work is based on observations made with the ESO telescopes. It made use of
which is rcirc ≃ 33 R⊙ currently for SS Lep. The expected ap- the Smithsonian/NASA’s Astrophysics Data System (ADS) and of the Centre de
parent diameter of this disc is between 0.8 and 1 mas if we take Donnees astronomiques de Strasbourg (CDS). All calculations and figures were
the inclination into account. This size is at the limit of detection performed with the freeware Yorick7 . The image reconstruction was performed
with our VLTI interferometric observations but is within reach with the software MIRA8 .
for CHARA instruments like MIRC or VEGA. We think this al-
ternative deserves further scrutiny.
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List of Objects
‘SS Leporis’ on page 1
8
9. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
Appendix A: Data and results of the parametric modelling
The interferometric data are plotted in Figs. A.1, A.2, and A.3 (visibilities and closure phases). The reduced data are available on Vizier/CDS. We also plotted on
these figures the visibilities and closure phases obtained from our binary model with the best parameters. Table A.1 and Fig. A.4 present the best parameters with
the data. We indicate for each observation which parameters are free in the fitting procedure. The relative fluxes are always free parameters and are considered to be
chromatic. Uncertainties on the fitted parameters were computed with Monte-Carlo simulations from the errors on the visibilities and closure phases.
50 50 50 50
V [106 rad−1]
V [106 rad−1]
V [106 rad−1]
V [106 rad−1]
0 0 0 0
−50 −50 −50 −50
−50 0 50 −50 0 50 −50 0 50 −50 0 50
U [106 rad−1] U [106 rad−1] U [106 rad−1] U [106 rad−1]
50 50 50 50
V [106 rad−1]
V [106 rad−1]
V [106 rad−1]
V [106 rad−1]
0 0 0 0
−50 −50 −50 −50
−50 0 50 −50 0 50 −50 0 50 −50 0 50
U [106 rad−1] U [106 rad−1] U [106 rad−1] U [106 rad−1]
Fig. A.1. (u,v)-plane coverage for observations of SS Lep (top: AMBER; bottom: PIONIER).
1.0 1.0 1.0 1.0
V2
V2
V2
V2
0.5 0.5 0.5 0.5
0.0 0.0 0.0 0.0
0 20 40 60 0 20 40 60 0 10 20 30 40 0 20 40 60
B/λ B/λ B/λ B/λ
1.0 1.0 1.0 1.0
V2
V2
V2
V2
0.5 0.5 0.5 0.5
0.0 0.0 0.0 0.0
0 20 40 0 10 20 30 40 0 10 20 30 40 0 20 40 60 80
B/λ B/λ B/λ B/λ
Fig. A.2. Visibility curves for the observations of SS Lep. The order of the figures corresponds to the (u,v)-plan coverages in Fig. A.1. In black are
the data with error bars. The visibility curves from our model with the best parameters are in red.
9
10. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
50 50 50 50
Phase closure
Phase closure
Phase closure
Phase closure
0 0 0 0
−50 −50 −50 −50
1.8 2.0 2.2 2.4 1.8 2.0 2.2 2.4 1.8 2.0 2.2 2.4 1.8 2.0 2.2 2.4
λ λ λ λ
50 50 50 50
Phase closure
Phase closure
Phase closure
Phase closure
0 0 0 0
−50 −50 −50 −50
1.60 1.65 1.70 1.75 1.80 1.60 1.65 1.70 1.75 1.80 1.60 1.65 1.70 1.75 1.80 1.6 1.7 1.8
λ λ λ λ
Fig. A.3. Closure phase curves for the observations for the observations of SS Lep. The order of the figures corresponds to the (u,v)-plan coverages
in Fig. A.1 In black are the data with error bars. The visibility curves from our model with the best parameters are in red.
1.0
relative flux
0.5
0.0
1.5 2.0 2.5
λ (µm)
Fig. A.4. Relative flux contribution of the M giant (red), the A star (blue), and the envelope (magenta). The different symbols represent the different
observations A1 (+), A3 (×), P1 ( ), P2 (△), P3 (▽), P4 (⃝).
10
11. N. Blind et al.: An incisive look at the symbiotic star SS Leporis
Table A.1. Most reliable parameters obtained with the 8 data sets.
ΦM ΦD a θ χ2
r
[mas] [mas] [mas] [deg]
Period A1: m jd ∼ 54781 and 54783 (AMBER data)
Free ? Yes Yes Yes Yes
Value 2.24 12.35 4.2 135 0.71
Error (1-σ) 2.7 × 10−2 2.3 × 10−1 3.5 × 10−2 0.35
Period A2: m jd ∼ 54826 (AMBER data)
Free ? Yes No Yes Yes
Value 2.05 12.2 3.8 69 0.20
Error (1-σ) 2.9 × 10−2 - 4.9 × 10−2 0.53
Period A3: m jd ∼ 54883 and 54890 (AMBER data)
Free ? Yes Yes Yes Yes
Value 2.14 12.2 4.5 347 1.36
Error (1-σ) 4.3 × 10−2 2.3 × 10−1 3.8 × 10−2 0.37
Period A4: m jd ∼ 54928 (AMBER data)
Free ? Yes No Yes Yes
Value 1.98 12.2 4.2 291 1.62
Error (1-σ) 3.9 × 10−2 - 4.0 × 10−2 0.47
Period P1: m jd ∼ 55500 (PIONIER data)
Free ? Yes No Yes Yes
Value 2.17 12.2 3.9 32 1.58
Error (1-σ) 1.4 × 10−2 - 1.5 × 10−2 0.06
Period P2: m jd ∼ 55529 (PIONIER data)
Free ? Yes No Yes Yes
Value 2.27 12.2 4.5 351 2.46
Error (1-σ) 1.2 × 10−2 - 0.2 × 10−2 0.78
Period P3: m jd ∼ 55537 (PIONIER data)
Free ? Yes No Yes Yes
Value 2.19 12.2 4.5 346 0.96
Error (1-σ) 1.6 × 10−2 - 0.6 × 10−2 0.20
Period P4: m jd ∼ 55552 (PIONIER data)
Free ? Yes No Yes Yes
Value 2.30 12.2 4.42 330.6 0.96
Error (1-σ) 0.9 × 10−2 - 0.9 × 10−2 0.12
Notes. The errors are the result of Monte Carlo computations based on the error on the visbilities and closure phases measurements.ϕ M and ϕD
are the M star diameter and the dusty disc/envelope FWHM, respectively. a and θ are the visual separation and orientation of the binary. The last
column gives the final reduced χ2 of the fit.
11