Publications of Michaël Gillon
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See detailThe CARMENES search for exoplanets around M dwarfs. Two planets on opposite sides of the radius gap transiting the nearby M dwarf LTT 3780
Nowak, G.; Luque, R.; Parviainen, H. et al

in Astronomy and Astrophysics (2020), 642

We present the discovery and characterisation of two transiting planets observed by the Transiting Exoplanet Survey Satellite (TESS) orbiting the nearby (d[SUB]⋆[/SUB] ≈ 22 pc), bright (J ≈ 9 mag) M3.5 ... [more ▼]

We present the discovery and characterisation of two transiting planets observed by the Transiting Exoplanet Survey Satellite (TESS) orbiting the nearby (d[SUB]⋆[/SUB] ≈ 22 pc), bright (J ≈ 9 mag) M3.5 dwarf LTT 3780 (TOI-732). We confirm both planets and their association with LTT 3780 via ground-based photometry and determine their masses using precise radial velocities measured with the CARMENES spectrograph. Precise stellar parameters determined from CARMENES high-resolution spectra confirm that LTT 3780 is a mid-M dwarf with an effective temperature of T[SUB]eff[/SUB] = 3360 ± 51 K, a surface gravity of log g[SUB]⋆[/SUB] = 4.81 ± 0.04 (cgs), and an iron abundance of [Fe/H] = 0.09 ± 0.16 dex, with an inferred mass of M[SUB]⋆[/SUB] = 0.379 ± 0.016M[SUB]☉[/SUB] and a radius of R[SUB]⋆[/SUB] = 0.382 ± 0.012R[SUB]☉[/SUB]. The ultra-short-period planet LTT 3780 b (P[SUB]b[/SUB] = 0.77 d) with a radius of 1.35[SUB]-0.06[/SUB][SUP]+0.06[/SUP] R[SUB]⊕[/SUB], a mass of 2.34[SUP]-0.23[/SUP][SUB]+0.24[/SUB] M[SUB]⊕[/SUB], and a bulk density of 5.24[SUB]-0.81[/SUB][SUP]+0.94[/SUP] g cm[SUP]-3[/SUP] joins the population of Earth-size planets with rocky, terrestrial composition. The outer planet, LTT 3780 c, with an orbital period of 12.25 d, radius of 2.42[SUB]-0.10[/SUB][SUP]+0.10[/SUP] R[SUB]⊕[/SUB], mass of 6.29[SUB]-0.61[/SUB][SUP]+0.63[/SUP] M[SUB]⊕[/SUB], and mean density of 2.45[SUB]-0.37[/SUB][SUP]+0.44[/SUP] g cm[SUP]-3[/SUP] belongs to the population of dense sub-Neptunes. With the two planets located on opposite sides of the radius gap, this planetary system is anexcellent target for testing planetary formation, evolution, and atmospheric models. In particular, LTT 3780 c is an ideal object for atmospheric studies with the James Webb Space Telescope (JWST). [less ▲]

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See detailGJ 273: On the formation, dynamical evolution and habitability of a planetary system hosted by an M dwarf at 3.75 parsec
Pozuelos Romero, Francisco José ULiege; Suárez, Juan C.; de Elía, Gonzalo C. et al

in Astronomy and Astrophysics (2020), 641(A23), 19

Planets orbiting low-mass stars such as M dwarfs are now considered a cornerstone in the search for life-harbouring planets. GJ273 is a planetary system orbiting an M dwarf only 3.75 pc away, composed of ... [more ▼]

Planets orbiting low-mass stars such as M dwarfs are now considered a cornerstone in the search for life-harbouring planets. GJ273 is a planetary system orbiting an M dwarf only 3.75 pc away, composed of two confirmed planets, GJ273b and GJ273c, and two promising candidates, GJ273d and GJ273e. Planet GJ273b resides in the habitable zone. Currently, due to a lack of observed planetary transits, only the minimum masses of the planets are known.Despite being an interesting system, the GJ273 planetary system is still poorly studied. We aim at precisely determine the physical parameters of the individual planets, in particular to break the mass--inclination degeneracy to accurately determine the mass of the planets. Moreover, we present thorough characterisation of planet GJ273b in terms of its potential habitability. We explored the planetary formation and hydration phases of GJ273 during the first 100 Myr. Then, we analysed the stability of the system. We also searched for regions which may harbour minor bodies such as an asteroid belt and Kuiper belt analogues. We found that the four-planet configuration of the system allows us to break the mass-- inclination degeneracy with the following masses: $2.89\leq M_{\mathrm{b}}\leq3.03\,\mathrm{M}_\oplus$, $1.18\leq M_{\mathrm{c}}\leq1.24\,\mathrm{M}_\oplus$, $10.80\leq M_{\mathrm{d}}\leq11.35\,\mathrm{M}_\oplus$, and $9.30\leq M_{\mathrm{e}}\leq9.70\,\mathrm{M}_\oplus$. That is an Earth-mass planet, a super-Earth and two mini-Neptunes. Moreover, GJ273b is found to be an efficient water captor and GJ273c likely a dry planet. Several stable regions are predicted where minor bodies might reside. We comprehensively discuss the habitability of GJ273b. [less ▲]

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See detailTRAPPIST-1: Global Results of the Spitzer Exploration Science Program Red Worlds
Ducrot, Elsa ULiege; Gillon, Michaël ULiege; Delrez, Laetitia ULiege et al

in Astronomy and Astrophysics (2020), 640(A112), 44

With more than 1000 hours of observation from Feb 2016 to Oct 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12pc) ultracool dwarf ... [more ▼]

With more than 1000 hours of observation from Feb 2016 to Oct 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12pc) ultracool dwarf star orbited by seven transiting Earth-sized planets, all well-suited for a detailed atmospheric characterization with the upcoming JWST. In this paper, we present the global results of the project. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5 $\mu$m. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5 $\mu$m to constrain the brightness temperatures of their daysides. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We estimate for TRAPPIST-1 transit depth measurements mean noise floors of $\sim$35 and 25 ppm in channels 1 and 2 of Spitzer/IRAC, respectively. most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5 $\mu$m, and can only set 3$\sigma$ upper limits on their dayside brightness temperatures (611K for b 586K for c). [less ▲]

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See detailGlobal analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey
Lienhard, F.; Queloz, D.; Gillon, Michaël ULiege et al

in Monthly Notices of the Royal Astronomical Society (2020), 497(3), 3790

We conducted a global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey - a prototype of the SPECULOOS transit search conducted with the TRAPPIST-South robotic telescope in Chile from 2011 to 2017 ... [more ▼]

We conducted a global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey - a prototype of the SPECULOOS transit search conducted with the TRAPPIST-South robotic telescope in Chile from 2011 to 2017 - to estimate the occurrence rate of close-in planets such as TRAPPIST-1b orbiting ultra-cool dwarfs. For this purpose, the photometric data of 40 nearby ultra-cool dwarfs were reanalysed in a self-consistent and fully automated manner starting from the raw images. The pipeline developed specifically for this task generates differential light curves, removes non-planetary photometric features and stellar variability, and searches for transits. It identifies the transits of TRAPPIST-1b and TRAPPIST-1c without any human intervention. To test the pipeline and the potential output of similar surveys, we injected planetary transits into the light curves on a star-by-star basis and tested whether the pipeline is able to detect them. The achieved photometric precision enables us to identify Earth-sized planets orbiting ultra-cool dwarfs as validated by the injection tests. Our planet-injection simulation further suggests a lower limit of 10 per cent on the occurrence rate of planets similar to TRAPPIST-1b with a radius between 1 and 1.3 R[SUB]⊕[/SUB] and the orbital period between 1.4 and 1.8 d. [less ▲]

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See detailThree short-period Jupiters from TESS. HIP 65Ab, TOI-157b, and TOI-169b
Nielsen, L. D.; Brahm, R.; Bouchy, F. et al

in Astronomy and Astrophysics (2020), 639

We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period ... [more ▼]

We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period Jupiter orbiting a bright (V = 11.1 mag) K4-dwarf every 0.98 days. It is a massive 3.213 ± 0.078 M[SUB]J[/SUB] planet in a grazing transit configuration with an impact parameter of b = 1.17[SUB]-0.08[/SUB][SUP]+0.10[/SUP]. As a result the radius is poorly constrained, 2.03[SUB]-0.49[/SUB][SUP]+0.61[/SUP]R[SUB]J[/SUB]. The planet's distance to its host star is less than twice the separation at which it would be destroyed by Roche lobe overflow. It is expected to spiral into HIP 65A on a timescale ranging from 80 Myr to a few gigayears, assuming a reduced tidal dissipation quality factor of Q[SUB]s[/SUB][SUP]'[/SUP] = 10[SUP]7[/SUP] - 10[SUP]9[/SUP]. We performed a full phase-curve analysis of the TESS data and detected both illumination- and ellipsoidal variations as well as Doppler boosting. HIP 65A is part of a binary stellar system, with HIP 65B separated by 269 AU (3.95 arcsec on sky). TOI-157b (TIC 140691463) is a typical hot Jupiter with a mass of 1.18 ± 0.13 M[SUB]J[/SUB] and a radius of 1.29 ± 0.02 R[SUB]J[/SUB]. It has a period of 2.08 days, which corresponds to a separation of just 0.03 AU. This makes TOI-157 an interesting system, as the host star is an evolved G9 sub-giant star (V = 12.7). TOI-169b (TIC 183120439) is a bloated Jupiter orbiting a V = 12.4 G-type star. It has a mass of 0.79 ±0.06 M[SUB]J[/SUB] and a radius of 1.09[SUB]-0.05[/SUB][SUP]+0.08[/SUP]R[SUB]J[/SUB]. Despite having the longest orbital period (P = 2.26 days) of the three planets, TOI-169b receives the most irradiation and is situated on the edge of the Neptune desert. All three host stars are metal rich with [Fe / H] ranging from 0.18 to0.24. [less ▲]

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See detailA Rare Pair of Eclipsing Brown Dwarfs Identified by the SPECULOOS Telescopes
Triaud, A. H. M. J.; Burgasser, A. J.; Burdanov, A. et al

in The Messenger (2020), 180

Brown dwarfs — stellar objects unable to sustain hydrogen fusion in their cores because of their low masses — continuously cool over their lifetimes. Evolution models have been created to reproduce this ... [more ▼]

Brown dwarfs — stellar objects unable to sustain hydrogen fusion in their cores because of their low masses — continuously cool over their lifetimes. Evolution models have been created to reproduce this behaviour, and to allow mass and age determination using their luminosity, temperatures, spectral types and other parameters. However, these models have not yet been fully validated or calibrated with observations. During a commissioning run of the SPECULOOS telescopes, we serendipitously discovered a rare double-line eclipsing binary, a member of the 45 Myr-old moving group Argus. This discovery permitted us to determine the masses, radii and ages of the brown dwarfs, and with their luminosities make a comparison to evolution models. The models reproduce these measurements remarkably well, although a measured offset in luminosity could result in systematic underestimation of brown dwarf masses by 20 to 30%. Calibrating these models is necessary as they are also used to infer the masses of young, directly imaged exoplanets such as those found at the VLT. [less ▲]

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See detailTwo Transiting Hot Jupiters from the WASP Survey: WASP-150b and WASP-176b
Cooke, Benjamin F.; Pollacco, Don; Almleaky, Y. et al

in Astronomical Journal (2020), 159

We report the discovery of two transiting exoplanets from the WASP survey, WASP-150b and WASP-176b. WASP-150b is an eccentric (e = 0.38) hot Jupiter on a 5.6 day orbit around a V = 12.03, F8 main-sequence ... [more ▼]

We report the discovery of two transiting exoplanets from the WASP survey, WASP-150b and WASP-176b. WASP-150b is an eccentric (e = 0.38) hot Jupiter on a 5.6 day orbit around a V = 12.03, F8 main-sequence host. The host star has a mass and radius of 1.4 ${M}_{\odot }$ and 1.7 ${R}_{\odot }$ respectively. WASP-150b has a mass and radius of 8.5 ${M}_{{\rm{J}}}$ and 1.1 R[SUB]J[/SUB], leading to a large planetary bulk density of 6.4 ρ[SUB]J[/SUB]. WASP-150b is found to be ∼3 Gyr old, well below its circularization timescale, supporting the eccentric nature of the planet. WASP-176b is a hot Jupiter planet on a 3.9 day orbit around a V = 12.01, F9 sub-giant host. The host star has a mass and radius of 1.3 M[SUB]☉[/SUB] and 1.9 R[SUB]☉[/SUB]. WASP-176b has a mass and radius of 0.86 M[SUB]J[/SUB] and 1.5 R[SUB]J[/SUB], respectively, leading to a planetary bulk density of 0.23 ρ[SUB]J[/SUB]. [less ▲]

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See detailPhotometry and performance of SPECULOOS-South
Murray, C. A.; Delrez, Laetitia ULiege; Pedersen, P. P. et al

in Monthly Notices of the Royal Astronomical Society (2020), 495

SPECULOOS-South, an observatory composed of four independent 1-m robotic telescopes, located at ESO Paranal, Chile, started scientific operation in 2019 January. This Southern hemisphere facility operates ... [more ▼]

SPECULOOS-South, an observatory composed of four independent 1-m robotic telescopes, located at ESO Paranal, Chile, started scientific operation in 2019 January. This Southern hemisphere facility operates as part of the Search for Habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS), an international network of 1-m-class telescopes surveying for transiting terrestrial planets around the nearest and brightest ultracool dwarfs (UCDs). To automatically and efficiently process the observations of SPECULOOS-South, and to deal with the specialized photometric requirements of UCD targets, we present our automatic pipeline. This pipeline includes an algorithm for automated differential photometry and an extensive correction technique for the effects of telluric water vapour, using ground measurements of the precipitable water vapour. Observing very red targets in the near-infrared can result in photometric systematics in the differential light curves, related to the temporally-varying, wavelength-dependent opacity of the Earth's atmosphere. These systematics are sufficient to affect the daily quality of the light curves, the longer time-scale variability study of our targets and even mimic transit-like signals. Here we present the implementation and impact of our water vapour correction method. Using the 179 nights and 98 targets observed in the I + z' filter by SPECULOOS-South since 2019 January, we show the impressive photometric performance of the facility (with a median precision of ∼1.5 mmag for 30-min binning of the raw, non-detrended light curves) and assess its detection potential. We compare simultaneous observations with SPECULOOS-South and TESS, to show that we readily achieve high- precision, space-level photometry for bright, UCDs, highlighting SPECULOOS-South as the first facility of its kind. [less ▲]

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See detailDiscovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX survey
Krushinsky, Vadim; Benni, Paul; Burdanov, Artem et al

in Monthly Notices of the Royal Astronomical Society (2020), 493

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light ... [more ▼]

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows ∼0.2 mag ellipsoidal variability with a period of 0.297549 d and a short total eclipse of the WD. Based on our analysis of the spectral and photometric data, we estimated the parameters of the system. The K7V star is tidally deformed but does not fill its Roche lobe (the filling factor is about 0.86). The orbital inclination is i = 73.1° ± 0.2°, and the mass ratio is q = M[SUB]2[/SUB]/M[SUB]1[/SUB] ≈ 0.88. The parameters of the K7V star are M[SUB]2[/SUB] ≈ 0.64 M[SUB]☉[/SUB], R[SUB]2[/SUB] = 0.645 ± 0.012R[SUB]☉[/SUB], and T[SUB]2[/SUB] ≈ 4070 K. The parameters of the WD are M[SUB]1[/SUB] ≈ 0.72 M[SUB]☉[/SUB], R[SUB]1[/SUB] = 0.013 ± 0.003R[SUB]☉[/SUB], and T[SUB]1[/SUB] = 8700 ± 1100 K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the SDSS r filter, which is unusual for a system of a WD and a late main-sequence star. We suspect that this system is a product of the evolution of a common-envelope binary star, and that the WD accretes the stellar wind from the secondary star (the so-called low-accretion-rate polar, hereafter LARP). [less ▲]

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See detailThe Continuing Search for Evidence of Tidal Orbital Decay of Hot Jupiters
Patra, Kishore C.; Winn, Joshua N.; Holman, Matthew J. et al

in Astronomical Journal (2020), 159

Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit-timing measurements ... [more ▼]

Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit-timing measurements spanning more than a decade have revealed that the orbital period is decreasing at a rate of dP/dt ≈ 10^{-9}, corresponding to a reduced tidal quality factor of about 2 × 10[SUP]5[/SUP]. Here, we present a compilation of transit- timing data for WASP-12 and 11 other systems that are especially favorable for detecting orbital decay: KELT-16; WASP-18, 19, 43, 72, 103, 114, and 122; HAT-P-23; HATS-18; and OGLE-TR-56. For most of these systems we present new data that extend the time baseline over which observations have been performed. None of the systems besides WASP-12 display convincing evidence for period changes, with typical upper limits on dP/dt on the order of 10[SUP]-9[/SUP] or 10[SUP]-10[/SUP], and lower limits on the reduced tidal quality factor on the order of 10[SUP]5[/SUP]. One possible exception is WASP-19, which shows a statistically significant trend, although it may be a spurious effect of starspot activity. Further observations are encouraged. [less ▲]

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See detailHATS-47b, HATS-48Ab, HATS-49b, and HATS-72b: Four Warm Giant Planets Transiting K Dwarfs
Hartman, J. D.; Jordán, Andrés; Bayliss, D. et al

in Astronomical Journal (2020), 159

We report the discovery of four transiting giant planets around K dwarfs. The planets HATS-47b, HATS-48Ab, HATS-49b, and HATS-72b have masses of 0.369[SUB]-0.021[/SUB][SUP]+0.031[/SUP] M_{J}, 0.243[SUB]-0 ... [more ▼]

We report the discovery of four transiting giant planets around K dwarfs. The planets HATS-47b, HATS-48Ab, HATS-49b, and HATS-72b have masses of 0.369[SUB]-0.021[/SUB][SUP]+0.031[/SUP] M_{J}, 0.243[SUB]-0.030[/SUB][SUP]+0.022[/SUP] M_{J}, 0.353[SUB]-0.027[/SUB][SUP]+0.038[/SUP] M_{J}, and 0.1254± 0.0039 M_{J}, respectively, and radii of 1.117± 0.014 R_{J}, 0.800± 0.015 R_{J}, 0.765± 0.013 R_{J}, and 0.7224± 0.0032 R_{J}, respectively. The planets orbit close to their host stars with orbital periods of 3.9228 days, 3.1317 days, 4.1480 days, and 7.3279ays, respectively. The hosts are main-sequence K dwarfs with masses of 0.674[SUB]-0.012[/SUB][SUP]+0.016[/SUP] M_{☉}, 0.7279 ± 0.0066 M_{☉}, 0.7133± 0.0075 M_{☉}, and 0.7311± 0.0028, and with V-band magnitudes of V=14.829± 0.010, 14.35± 0.11, 14.998± 0.040 and 12.469± 0.010. The super-Neptune HATS-72b (a.k.a. WASP-191b and TOI 294.01) was independently identified as a transiting planet candidate by the HATSouth, WASP, and TESS surveys, and we present a combined analysis of all of the data gathered by each of these projects (and their follow-up programs). An exceptionally precise mass is measured for HATS-72b thanks to high-precision radial velocity (RV) measurements obtained with VLT/ESPRESSO, FEROS, HARPS, and Magellan/PFS. We also incorporate TESS observations of the warm Saturn─hosting systems HATS-47 (a.k.a. TOI 1073.01), HATS-48A, and HATS-49. HATS-47 was independently identified as a candidate by the TESS team, while the other two systems were not previously identified from the TESS data. The RV orbital variations are measured for these systems using Magellan/PFS. HATS-48A has a resolved 5.4" neighbor in Gaia DR2, which is a common-proper-motion binary star companion to HATS-48A with a mass of 0.22 M_{☉} and a current projected physical separation of ∼1400 au. [less ▲]

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See detailAn Eclipsing Substellar Binary in a Young Triple System discovered by SPECULOOS
Triaud, Amaury H. M. J.; Burgasser, Adam J.; Burdanov, Artem ULiege et al

in Nature Astronomy (2020), 4

Mass, radius, and age are three of the most fundamental parameters for celestial objects, enabling studies of the evolution and internal physics of stars, brown dwarfs, and planets. Brown dwarfs are ... [more ▼]

Mass, radius, and age are three of the most fundamental parameters for celestial objects, enabling studies of the evolution and internal physics of stars, brown dwarfs, and planets. Brown dwarfs are hydrogen- rich objects that are unable to sustain core fusion reactions but are supported from collapse by electron degeneracy pressure. As they age, brown dwarfs cool, reducing their radius and luminosity. Young exoplanets follow a similar behaviour. Brown dwarf evolutionary models are relied upon to infer the masses, radii and ages of these objects. Similar models are used to infer the mass and radius of directly imaged exoplanets. Unfortunately, only sparse empirical mass, radius and age measurements are currently available, and the models remain mostly unvalidated. Double-line eclipsing binaries provide the most direct route for the absolute determination of the masses and radii of stars. Here, we report the SPECULOOS discovery of 2M1510A, a nearby, eclipsing, double-line brown dwarf binary, with a widely-separated tertiary brown dwarf companion. We also find that the system is a member of the $45\pm5$ Myr-old moving group, Argus. The system's age matches those of currently known directly-imaged exoplanets. 2M1510A provides an opportunity to benchmark evolutionary models of brown dwarfs and young planets. We find that widely-used evolutionary models do reproduce the mass, radius and age of the binary components remarkably well, but overestimate the luminosity by up to 0.65 magnitudes, which could result in underestimated photometric masses for directly-imaged exoplanets and young field brown dwarfs by 20 to 35%. [less ▲]

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See detailTESS Spots a Hot Jupiter with an Inner Transiting Neptune
Huang, Chelsea X.; Quinn, Samuel N.; Vanderburg, Andrew et al

in Astrophysical Journal (2020), 892

Hot Jupiters are rarely accompanied by other planets within a factor of a few in orbital distance. Previously, only two such systems have been found. Here, we report the discovery of a third system using ... [more ▼]

Hot Jupiters are rarely accompanied by other planets within a factor of a few in orbital distance. Previously, only two such systems have been found. Here, we report the discovery of a third system using data from the Transiting Exoplanet Survey Satellite (TESS). The host star, TOI-1130, is an eleventh magnitude K-dwarf in Gaia G-band. It has two transiting planets: a Neptune-sized planet (3.65 ± 0.10 R[SUB]\oplus[/SUB]) with a 4.1 days period, and a hot Jupiter (1.50[SUB]-0.22[/SUB][SUP]+0.27[/SUP] R[SUB]J[/SUB]) with an 8.4 days period. Precise radial-velocity observations show that the mass of the hot Jupiter is 0.974[SUB]-0.044[/SUB][SUP]+0.043[/SUP] M[SUB]J[/SUB]. For the inner Neptune, the data provide only an upper limit on the mass of 0.17 M[SUB]J[/SUB] (3σ). Nevertheless, we are confident that the inner planet is real, based on follow-up ground-based photometry and adaptive-optics imaging that rule out other plausible sources of the TESS transit signal. The unusual planetary architecture of and the brightness of the host star make TOI-1130 a good test case for planet formation theories, and an attractive target for future spectroscopic observations. [less ▲]

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See detailLife under another Sun: From Science Fiction to Science
Gillon, Michaël ULiege

in European Review (2020), 28(1), 18-39

Initiated in the sixteenth century, the Copernican revolution toppled our Earth from its theological pedestal, revealing it not to be the centre of everything but a planet among several others in orbit ... [more ▼]

Initiated in the sixteenth century, the Copernican revolution toppled our Earth from its theological pedestal, revealing it not to be the centre of everything but a planet among several others in orbit around one of the zillions of stars of our Universe. Already proposed by some philosophers at the dawn of this major paradigm shift, the existence of exoplanets, i.e. planets in orbit around stars other than our Sun, remained suspected but unconfirmed for centuries. It is only in the last decade of the twentieth century that the first of these extrasolar worlds were found. Their seminal discoveries initiated the development of more and more ambitious projects that led eventually to the detection of thousands of exoplanets, including a few dozen potentially habitable ones, i.e. terrestrial exoplanets that could harbour large amounts of liquid water - and maybe life - on their surfaces. Upcoming astronomical facilities will soon be able to probe the atmospheric compositions of some of these extrasolar worlds, maybe performing in the process the historical detection of chemical signs of life light-years away. But while the existence of extraterrestrial life remains pure speculation for now, it has been a major theme of science fiction for more than a century. By creating countless stories of encounters between humans and alien forms of life, science-fiction authors have pursued, in a sense, the Copernican revolution, confronting us with the idea that not only could life be widespread in the Universe, but also that our species may be far from the Cosmic pinnacle in matters of intelligence and technological development. © Academia Europaea 2019. [less ▲]

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See detailMCMCI: A code to fully characterise an exoplanetary system
Bonfanti, A.; Gillon, Michaël ULiege

in Astronomy and Astrophysics (2020), 635

Context. Useful information can be retrieved by analysing the transit light curve of a planet-hosting star or induced radial velocity oscillations. However, inferring the physical parameters of the planet ... [more ▼]

Context. Useful information can be retrieved by analysing the transit light curve of a planet-hosting star or induced radial velocity oscillations. However, inferring the physical parameters of the planet, such as mass, size, and semi-major axis, requires preliminary knowledge of some parameters of the host star, especially its mass or radius, which are generally inferred through theoretical evolutionary models. Aims. We seek to present and test a whole algorithm devoted to the complete characterisation of an exoplanetary system thanks to the global analysis of photometric or radial velocity time series combined with observational stellar parameters derived either from spectroscopy or photometry. Methods. We developed an integrated tool called MCMCI. This tool combines the Markov chain Monte Carlo (MCMC) approach of analysing photometric or radial velocity time series with a proper interpolation within stellar evolutionary isochrones and tracks, known as isochrone placement, to be performed at each chain step, to retrieve stellar theoretical parameters such as age, mass, and radius. Results. We tested the MCMCI on the HD 219134 multi-planetary system hosting two transiting rocky super Earths and on WASP-4, which hosts a bloated hot Jupiter. Even considering different input approaches, a final convergence was reached within the code, we found good agreement with the results already stated in the literature and we obtained more precise output parameters, especially concerning planetary masses. Conclusions. The MCMCI tool offers the opportunity to perform an integrated analysis of an exoplanetary system without splitting it into the preliminary stellar characterisation through theoretical models. Rather this approach favours a close interaction between light curve analysis and isochrones, so that the parameters recovered at each step of the MCMC enter as inputs for purposes of isochrone placement. © 2020 ESO. [less ▲]

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See detailTOI-1338: TESS' First Transiting Circumbinary Planet
Kostov, V. B.; Orosz, J. A.; Feinstein, A. D. et al

in Astronomical Journal (2020), 159(6),

We report the detection of the first circumbinary planet (CBP) found by Transiting Exoplanet Survey Satellite (TESS). The target, a known eclipsing binary, was observed in sectors 1 through 12 at 30 ... [more ▼]

We report the detection of the first circumbinary planet (CBP) found by Transiting Exoplanet Survey Satellite (TESS). The target, a known eclipsing binary, was observed in sectors 1 through 12 at 30 minute cadence and in sectors 4 through 12 at 2 minute cadence. It consists of two stars with masses of 1.1 M o˙ and 0.3 M o˙ on a slightly eccentric (0.16), 14.6 day orbit, producing prominent primary eclipses and shallow secondary eclipses. The planet has a radius of ∼6.9 R ⊕ and was observed to make three transits across the primary star of roughly equal depths (∼0.2%) but different durations-a common signature of transiting CBPs. Its orbit is nearly circular (e ≈ 0.09) with an orbital period of 95.2 days. The orbital planes of the binary and the planet are aligned to within ∼1°. To obtain a complete solution for the system, we combined the TESS photometry with existing ground-based radial-velocity observations in a numerical photometric-dynamical model. The system demonstrates the discovery potential of TESS for CBPs and provides further understanding of the formation and evolution of planets orbiting close binary stars. © 2020. The American Astronomical Society. All rights reserved. [less ▲]

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See detailThe CHEOPS mission
Benz, Willy; Broeg, Christopher; Fortier, Andrea et al

in Experimental Astronomy (2020)

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See detailMCMCI: A code to fully characterise an exoplanetary system
Bonfanti, Andrea ULiege; Gillon, Michaël ULiege

E-print/Working paper (2019)

Useful information can be retrieved by analysing the transit light curve of a planet-hosting star or induced radial velocity oscillations. However, inferring the physical parameters of the planet, such as ... [more ▼]

Useful information can be retrieved by analysing the transit light curve of a planet-hosting star or induced radial velocity oscillations. However, inferring the physical parameters of the planet, such as mass, size, and semi-major axis, requires preliminary knowledge of some parameters of the host star, especially its mass or radius, which are generally inferred through theoretical evolutionary models. We seek to present and test a whole algorithm devoted to the complete characterisation of an exoplanetary system thanks to the global analysis of photometric or radial velocity time series combined with observational stellar parameters derived either from spectroscopy or photometry. We developed an integrated tool called MCMCI. This tool combines the Markov chain Monte Carlo (MCMC) approach of analysing photometric or radial velocity time series with a proper interpolation within stellar evolutionary isochrones and tracks, known as isochrone placement, to be performed at each chain step, to retrieve stellar theoretical parameters such as age, mass, and radius. We tested the MCMCI on the HD 219134 multi-planetary system hosting two transiting rocky super Earths and on WASP-4, which hosts a bloated hot Jupiter. Even considering different input approaches, a final convergence was reached within the code, we found good agreement with the results already stated in the literature and we obtained more precise output parameters, especially concerning planetary masses. The MCMCI tool offers the opportunity to perform an integrated analysis of an exoplanetary system without splitting it into the preliminary stellar characterisation through theoretical models. Rather this approach favours a close interaction between light curve analysis and isochrones, so that the parameters recovered at each step of the MCMC enter as inputs for purposes of isochrone placement. [less ▲]

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See detailWASP-South hot Jupiters: WASP-178b, WASP-184b, WASP-185b, and WASP-192b
Hellier, Coel; Anderson, D. R.; Barkaoui, Khalid ULiege et al

in Monthly Notices of the Royal Astronomical Society (2019), 490

We report on four new transiting hot Jupiters discovered by the WASP- South survey. WASP-178b transits a V = 9.9, A1V star with T[SUB]eff[/SUB] = 9350 ± 150 K, the second-hottest transit host known. It ... [more ▼]

We report on four new transiting hot Jupiters discovered by the WASP- South survey. WASP-178b transits a V = 9.9, A1V star with T[SUB]eff[/SUB] = 9350 ± 150 K, the second-hottest transit host known. It has a highly bloated radius of 1.81 ± 0.09 R[SUB]Jup[/SUB], in line with the known correlation between high irradiation and large size. With an estimated temperature of 2470 ± 60 K, the planet is one of the best targets for studying ultrahot Jupiters that is visible from the Southern hemisphere. The three host stars WASP-184, WASP-185, and WASP-192 are all post-main-sequence G0 stars of ages 4-8 Gyr. The larger stellar radii (1.3-1.7 M[SUB]☉[/SUB]) mean that the transits are relatively shallow (0.7-0.9 per cent) even though the planets have moderately inflated radii of 1.2-1.3 R[SUB]Jup[/SUB]. WASP-185b has an eccentric orbit (e = 0.24) and a relatively long orbital period of 9.4 d. A star that is 4.6 arcsec from WASP-185 and 4.4 mag fainter might be physically associated. [less ▲]

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See detailA super-solar metallicity atmosphere for WASP-127b revealed by transmission spectroscopy from HST and Spitzer
Spake, Jessica J.; Sing, David K.; Wakeford, Hannah R. et al

E-print/Working paper (2019)

The chemical abundances of exoplanet atmospheres may provide valuable information about the bulk compositions, formation pathways, and evolutionary histories of planets. Exoplanets which have large ... [more ▼]

The chemical abundances of exoplanet atmospheres may provide valuable information about the bulk compositions, formation pathways, and evolutionary histories of planets. Exoplanets which have large, relatively cloud-free atmospheres, and which orbit bright stars provide the best opportunities for accurate abundance measurements. For this reason, we measured the transmission spectrum of the bright (V~10.2), large (1.37RJ), sub-Saturn mass (0.19MJ) exoplanet WASP-127b across the near-UV to near-infrared wavelength range (0.3 - 5 microns), using the Hubble and Spitzer Space Telescopes. Our results show a feature-rich transmission spectrum, with absorption from Na, H2O, and CO2, as well as wavelength-dependent scattering from small-particle condensates, and a grey absorber which somewhat mutes the molecular absorption features. We ran two types of atmospheric retrieval models: one enforcing chemical equilibrium, and the other which fit the abundances freely. Our retrieved abundances at chemical equilibrium for Na, O and C are all super-solar, with abundances relative to solar values of 51+30-29, 23+15-9, and 33+43-25 respectively. Despite giving conflicting C/O ratios, both retrievals gave super-solar CO2 volume mixing ratios, which adds to the likelihood that WASP-127b's bulk metallicity is super-solar, since CO2 abundance is highly sensitive to atmospheric metallicity. In the future, spectroscopy with JWST will be able to constrain WASP-127b's C/O ratio, and may reveal the formation history of this metal-enriched, highly observable exoplanet. [less ▲]

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