Andrea Fortier - Academia.edu (original) (raw)
Papers by Andrea Fortier
Monthly Notices of the Royal Astronomical Society
ABSTRACTWe present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data ... more ABSTRACTWe present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82-d orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60-d orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 min for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.
arXiv (Cornell University), Nov 25, 2022
Context. Stellar granulation generates fluctuations in photometric and spectroscopic data whose p... more Context. Stellar granulation generates fluctuations in photometric and spectroscopic data whose properties depend on the stellar type, composition, and evolutionary state. Characterizing granulation is key for understanding stellar atmospheres and detecting planets. Aims. We aim to detect the signatures of stellar granulation, link spectroscopic and photometric signatures of convection for main-sequence stars, and test predictions from 3D hydrodynamic models. Methods. For the first time, we observed two bright stars (T eff = 5833 K and 6205 K) with high-precision observations taken simultaneously with CHEOPS and ESPRESSO. We analyzed the properties of the stellar granulation signal in each individual dataset. We compared them to Kepler observations and 3D hydrodynamic models. While isolating the granulation-induced changes by attenuating and filtering the p-mode oscillation signals, we studied the relationship between photometric and spectroscopic observables. Results. The signature of stellar granulation is detected and precisely characterized for the hotter F star in the CHEOPS and ESPRESSO observations. For the cooler G star, we obtain a clear detection in the CHEOPS dataset only. The TESS observations are blind to this stellar signal. Based on CHEOPS observations, we show that the inferred properties of stellar granulation are in agreement with both Kepler observations and hydrodynamic models. Comparing their periodograms, we observe a strong link between spectroscopic and photometric observables. Correlations of this stellar signal in the time domain (flux versus radial velocities, RV) and with specific spectroscopic observables (shape of the cross-correlation functions) are however difficult to isolate due to S/N dependent variations. Conclusions. In the context of the upcoming PLATO mission and the extreme precision RV surveys, a thorough understanding of the properties of the stellar granulation signal is needed. The CHEOPS and ESPRESSO observations pave the way for detailed analyses of this stellar process.
Astronomy & Astrophysics
Context. Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only ... more Context. Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only observationally confirmed case of this being WASP-12b. By examining this effect, information on the properties of the host star can be obtained using the so-called stellar modified tidal quality factor Q*′, which describes the efficiency with which the kinetic energy of the planet is dissipated within the star. This can provide information about the interior of the star. Aims. In this study, we aim to improve constraints on the tidal decay of the KELT-9, KELT-16, and WASP-4 systems in order to find evidence for or against the presence of tidal orbital decay. With this, we want to constrain the Q*′ value for each star. In addition, we aim to test the existence of the transit timing variations (TTVs) in the HD 97658 system, which previously favoured a quadratic trend with increasing orbital period. Methods. Making use of newly acquired photometric observations from CHEOPS (CHaracterising E...
arXiv (Cornell University), Nov 7, 2022
Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obta... more Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obtained at visible and infrared wavelengths have been challenging to reconcile with a planetary reflection and emission model. In this study, we analyse a set of 41 occultations obtained over a two-year timespan with the CHEOPS satellite. We report the detection of 55 Cnc e's occultation with an average depth of 12 ± 3 ppm. We derive a corresponding 2-σ upper limit on the geometric albedo of A g < 0.55 once decontaminated from the thermal emission measured by Spitzer at 4.5µm. CHEOPS's photometric performance enables, for the first time, the detection of individual occultations of this super-Earth in the visible and identifies short-timescale photometric corrugations likely induced by stellar granulation. We also find a clear 47.3-day sinusoidal pattern in the time-dependent occultation depths that we are unable to relate to stellar noise, nor instrumental systematics, but whose planetary origin could be tested with upcoming JWST occultation observations of this iconic super-Earth.
Astronomy & Astrophysics
Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obta... more Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obtained at visible and infrared wavelengths have been challenging to reconcile with a planetary reflection and emission model. In this study, we analyse a set of 41 occultations obtained over a two-year timespan with the CHEOPS satellite. We report the detection of 55 Cnc e’s occultation with an average depth of 12 ± 3 ppm. We derive a corresponding 2σ upper limit on the geometric albedo of Ag < 0.55 once decontaminated from the thermal emission measured by Spitzer at 4.5 µm. CHEOPS’s photometric performance enables, for the first time, the detection of individual occultations of this super-Earth in the visible and identifies short-timescale photometric corrugations likely induced by stellar granulation. We also find a clear 47.3-day sinusoidal pattern in the time-dependent occultation depths that we are unable to relate to stellar noise, nor instrumental systematics, but whose planetary...
Monthly Notices of the Royal Astronomical Society
EBLM J0113+31 is moderately bright (V=10.1), metal-poor ([Fe/H] ≈−0.3) G0V star with a much faint... more EBLM J0113+31 is moderately bright (V=10.1), metal-poor ([Fe/H] ≈−0.3) G0V star with a much fainter M dwarf companion on a wide, eccentric orbit (=14.3 d). We have used near-infrared spectroscopy obtained with the SPIRou spectrograph to measure the semi-amplitude of the M dwarf’s spectroscopic orbit, and high-precision photometry of the eclipse and transit from the CHEOPS and TESS space missions to measure the geometry of this binary system. From the combined analysis of these data together with previously published observations we obtain the following model-independent masses and radii: M1 = 1.029 ± 0.025M⊙, M2 = 0.197 ± 0.003M⊙, R1 = 1.417 ± 0.014R⊙, R2 = 0.215 ± 0.002R⊙. Using R1 and the parallax from Gaia EDR3 we find that this star’s angular diameter is θ = 0.0745 ± 0.0007 mas. The apparent bolometric flux of the G0V star corrected for both extinction and the contribution from the M dwarf (<0.2 per cent) is mathcalFoplus,0=(2.62pm0.05)times10−9{\mathcal {F}}_{\oplus ,0} = (2.62\pm 0.05)\times 10^{-9}mathcalFoplus,0=(2.62pm0.05)times10−9 erg cm−2...
VizieR Online Data Catalog (other), Jun 1, 2021
VizieR Online Data Catalog, Sep 1, 2020
Astronomy & Astrophysics, 2022
Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as dete... more Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as detected in combined TESS (2018, 2020) and CHEOPS (2020, 2021) transit observations. AU Mic is a young planetary system with a debris disk and two transiting warm Neptunes. A TTV on the order of several minutes was previously reported for AU Mic b, which was suggested to be an outcome of mutual perturbations between the planets in the system. In 2021, we observed AU Mic b (five transits) and c (three transits) with the CHEOPS space telescope to follow-up the TTV of AU Mic b and possibly detect a TTV for AU Mic c. When analyzing TESS and CHEOPS 2020−2021 measurements together, we find that a prominent TTV emerges with a full span of ≥23 min between the two TTV extrema. Assuming that the period change results from a periodic process –such as mutual perturbations– we demonstrate that the times of transits in the summer of 2022 are expected to be 30−85 min later than predicted by the available l...
Astronomy & Astrophysics, 2021
Context. Hot subdwarfs experienced strong mass loss on the red giant branch (RGB) and are now hot... more Context. Hot subdwarfs experienced strong mass loss on the red giant branch (RGB) and are now hot and small He-burning objects. These stars constitute excellent opportunities for addressing the question of the evolution of exoplanetary systems directly after the RGB phase of evolution. Aims. In this project we aim to perform a transit survey in all available light curves of hot subdwarfs from space-based telescopes (Kepler, K2, TESS, and CHEOPS) with our custom-made pipeline SHERLOCK in order to determine the occurrence rate of planets around these stars as a function of orbital period and planetary radius. We also aim to determine whether planets that were previously engulfed in the envelope of their red giant host star can survive, even partially, as a planetary remnant. Methods. For this first paper, we performed injection-and-recovery tests of synthetic transits for a selection of representative Kepler, K2, and TESS light curves to determine which transiting bodies in terms of o...
CHEOPS (CHaracterising ExOPlanet Satellite) is the first ESA Small Mission as part of the ESA Cos... more CHEOPS (CHaracterising ExOPlanet Satellite) is the first ESA Small Mission as part of the ESA Cosmic Vision program 2015-2025 and it is planned launch readiness end of 2017. The mission lead is performed in a partnership between Switzerland, led by the University of Bern, and the European Space Agency with important contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS mission will be the first space telescope dedicated to search for exoplanetary transits on bright stars already known to host planets by performing ultrahigh precision photometry on bright starts whose mass has been already estimated through spectroscopic surveys on ground based observations. The number of exoplanets in the mass range 1-30 MEarth for which both mass and radius are known with a good precision is extremely limited also considering the last two decades of high-precision radial velocity measurement campaigns and the highly success...
Presentamos nuestros resultados sobre la formación de planetas gigantes dentro del marco del meca... more Presentamos nuestros resultados sobre la formación de planetas gigantes dentro del marco del mecanismo de inestabilidad nucleada. Consideramos el régimen de crecimiento oligárquico para el núcleo sólido y una reducción en la opacidad de los granos. Bajo estas suposiciones, la formación de planetas gigantes in situ se puede alcanzar en una escala de tiempo más corta que la duración de vida de discos protoplanetarios.
Context. A large sample of long-period giant planets has been discovered thanks to long-term radi... more Context. A large sample of long-period giant planets has been discovered thanks to long-term radial velocity surveys, but only a few dozen of these planets have a precise radius measurement. Transiting gas giants are crucial targets for the study of atmospheric composition across a wide range of equilibrium temperatures and, more importantly, for shedding light on the formation and evolution of planetary systems. Indeed, compared to hot Jupiters, the atmospheric properties and orbital parameters of cooler gas giants are unaltered by intense stellar irradiation and tidal effects. Aims. We aim to identify long-period planets in the Transiting Exoplanet Survey Satellite (TESS) data as single or duo-transit events. Our goal is to solve the orbital periods of TESS duo-transit candidates with the use of additional space-based photometric observations and to collect follow-up spectroscopic observations in order to confirm the planetary nature and measure the mass of the candidates. Methods. We use the CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability period aliases in order to discard or confirm a transit event at a given period. Once a period is confirmed, we jointly model the TESS and CHEOPS light curves along with the radial velocity datasets to measure the orbital parameters of the system and obtain precise mass and radius measurements. Results. We report the discovery of a long-period transiting Neptune-mass planet orbiting the G7-type star TOI-5678. Our spectroscopic analysis shows that TOI-5678 is a star with a solar metallicity. The TESS light curve of TOI-5678 presents two transit events separated by almost two years. In addition, CHEOPS observed the target as part of its Guaranteed Time Observation program. After four non-detections corresponding to possible periods, CHEOPS detected a transit event matching a unique period alias. Follow-up radial velocity observations were carried out with the ground-based high-resolution spectrographs CORALIE and HARPS. Joint modeling reveals that TOI-5678 hosts a 47.73 day period planet, and we measure an orbital eccentricity consistent with zero at 2σ. The planet TOI-5678 b has a mass of 20 ± 4 Earth masses (M ⊕) and a radius of 4.91 ± 0.08 R ⊕. Using interior structure modeling, we find that TOI-5678 b is composed of a low-mass core surrounded by a large H/He layer with a mass of 3.2 +1.7 −1.3 M ⊕. Conclusions. TOI-5678 b is part of a growing sample of well-characterized transiting gas giants receiving moderate amounts of stellar insolation (11 S ⊕). Precise density measurement gives us insight into their interior composition, and the objects orbiting bright stars are suitable targets to study the atmospheric composition of cooler gas giants. Key words. planets and satellites: detection-planets and satellites: individual: TOI-5678-planets and satellites: gaseous planetsmethods: data analysis ⋆ Full Table 2 and reduced CHEOPS and HARPS data are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr
Astronomy & Astrophysics, 2021
Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 ma... more Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 mag) star HD 108236 (also known as TOI-1233) was recently reported on the basis of TESS and ground-based light curves. Aims. We perform a first characterisation of the HD 108236 planetary system through high-precision CHEOPS photometry and improve the transit ephemerides and system parameters. Methods. We characterise the host star through spectroscopic analysis and derive the radius with the infrared flux method. We constrain the stellar mass and age by combining the results obtained from two sets of stellar evolutionary tracks. We analyse the available TESS light curves and one CHEOPS transit light curve for each known planet in the system. Results. We find that HD 108236 is a Sun-like star with R⋆ = 0.877 ± 0.008 R⊙, M⋆ = 0.869−0.048+0.050 M⊙, and an age of 6.7−5.1+4.0 Gyr. We report the serendipitous detection of an additional planet, HD 108236 f, in one of the CHEOPS light curves. For...
Giant planet formation process is still not completely understood. The current most accepted para... more Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the solar system’s giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks ’ lifetimes, especially for the cases of Uranus and Neptune. In the context of this model, and considering a recently proposed primordial solar system orbital structure, we performed numerical calculations of giant planet formation. Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30-100 meter sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario. The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.
Monthly Notices of the Royal Astronomical Society, 2021
CHEOPS (CHaracterising ExOPlanet Satellite) is an ESA S-class mission that observes bright stars ... more CHEOPS (CHaracterising ExOPlanet Satellite) is an ESA S-class mission that observes bright stars at high cadence from low-Earth orbit. The main aim of the mission is to characterize exoplanets that transit nearby stars using ultrahigh precision photometry. Here, we report the analysis of transits observed by CHEOPS during its Early Science observing programme for four well-known exoplanets: GJ 436 b, HD 106315 b, HD 97658 b, and GJ 1132 b. The analysis is done using pycheops, an open-source software package we have developed to easily and efficiently analyse CHEOPS light-curve data using state-of-the-art techniques that are fully described herein. We show that the precision of the transit parameters measured using CHEOPS is comparable to that from larger space telescopes such as Spitzer Space Telescope and Kepler. We use the updated planet parameters from our analysis to derive new constraints on the internal structure of these four exoplanets.
Proceedings of the International Astronomical Union, 2010
Photometric observations of transits can be used to derive physical and orbital parameters of the... more Photometric observations of transits can be used to derive physical and orbital parameters of the system, like the planetary and stellar radius, orbital inclination and mean density of the star. Furthermore, monitoring possible periodic variations in transit timing of planets is important, since small changes can be caused by the presence of other planets or moons in the system. On the other hand, long term changes in the transit length can be due to the orbital precession of the planets. For these reasons we started an observational program dedicated to observe transits of known exoplanets with the aim of contributing to a better understanding of these planetary systems. In this work we present our first results obtained using the observational facilities in Argentina including the 2.15 telescope at CASLEO.
In the frame of the core instability model, we present calculations of in situ giant planet forma... more In the frame of the core instability model, we present calculations of in situ giant planet formation introducing the oligarchic growth regime of planetesimals as the time dependent core accretion rate. As giant planets are mainly composed of gas, to obtain a self consistent oligarchic core accretion rate, an accurate model of its atmosphere's structure has to be considered in the calculation of the effective cross section for planetesimal capture. We made several simulations of the formation of a Jupiter like object. Including the gas drag effect of the protoplanet's atmosphere produces an important enhancement on its effective capture radius leading to a timescale reduction but duplicating the final mass of solids accreted. FULL TEXT IN SPANISH
Monthly Notices of the Royal Astronomical Society
ABSTRACTWe present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data ... more ABSTRACTWe present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82-d orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60-d orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 min for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.
arXiv (Cornell University), Nov 25, 2022
Context. Stellar granulation generates fluctuations in photometric and spectroscopic data whose p... more Context. Stellar granulation generates fluctuations in photometric and spectroscopic data whose properties depend on the stellar type, composition, and evolutionary state. Characterizing granulation is key for understanding stellar atmospheres and detecting planets. Aims. We aim to detect the signatures of stellar granulation, link spectroscopic and photometric signatures of convection for main-sequence stars, and test predictions from 3D hydrodynamic models. Methods. For the first time, we observed two bright stars (T eff = 5833 K and 6205 K) with high-precision observations taken simultaneously with CHEOPS and ESPRESSO. We analyzed the properties of the stellar granulation signal in each individual dataset. We compared them to Kepler observations and 3D hydrodynamic models. While isolating the granulation-induced changes by attenuating and filtering the p-mode oscillation signals, we studied the relationship between photometric and spectroscopic observables. Results. The signature of stellar granulation is detected and precisely characterized for the hotter F star in the CHEOPS and ESPRESSO observations. For the cooler G star, we obtain a clear detection in the CHEOPS dataset only. The TESS observations are blind to this stellar signal. Based on CHEOPS observations, we show that the inferred properties of stellar granulation are in agreement with both Kepler observations and hydrodynamic models. Comparing their periodograms, we observe a strong link between spectroscopic and photometric observables. Correlations of this stellar signal in the time domain (flux versus radial velocities, RV) and with specific spectroscopic observables (shape of the cross-correlation functions) are however difficult to isolate due to S/N dependent variations. Conclusions. In the context of the upcoming PLATO mission and the extreme precision RV surveys, a thorough understanding of the properties of the stellar granulation signal is needed. The CHEOPS and ESPRESSO observations pave the way for detailed analyses of this stellar process.
Astronomy & Astrophysics
Context. Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only ... more Context. Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only observationally confirmed case of this being WASP-12b. By examining this effect, information on the properties of the host star can be obtained using the so-called stellar modified tidal quality factor Q*′, which describes the efficiency with which the kinetic energy of the planet is dissipated within the star. This can provide information about the interior of the star. Aims. In this study, we aim to improve constraints on the tidal decay of the KELT-9, KELT-16, and WASP-4 systems in order to find evidence for or against the presence of tidal orbital decay. With this, we want to constrain the Q*′ value for each star. In addition, we aim to test the existence of the transit timing variations (TTVs) in the HD 97658 system, which previously favoured a quadratic trend with increasing orbital period. Methods. Making use of newly acquired photometric observations from CHEOPS (CHaracterising E...
arXiv (Cornell University), Nov 7, 2022
Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obta... more Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obtained at visible and infrared wavelengths have been challenging to reconcile with a planetary reflection and emission model. In this study, we analyse a set of 41 occultations obtained over a two-year timespan with the CHEOPS satellite. We report the detection of 55 Cnc e's occultation with an average depth of 12 ± 3 ppm. We derive a corresponding 2-σ upper limit on the geometric albedo of A g < 0.55 once decontaminated from the thermal emission measured by Spitzer at 4.5µm. CHEOPS's photometric performance enables, for the first time, the detection of individual occultations of this super-Earth in the visible and identifies short-timescale photometric corrugations likely induced by stellar granulation. We also find a clear 47.3-day sinusoidal pattern in the time-dependent occultation depths that we are unable to relate to stellar noise, nor instrumental systematics, but whose planetary origin could be tested with upcoming JWST occultation observations of this iconic super-Earth.
Astronomy & Astrophysics
Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obta... more Past occultation and phase-curve observations of the ultra-short period super-Earth 55 Cnc e obtained at visible and infrared wavelengths have been challenging to reconcile with a planetary reflection and emission model. In this study, we analyse a set of 41 occultations obtained over a two-year timespan with the CHEOPS satellite. We report the detection of 55 Cnc e’s occultation with an average depth of 12 ± 3 ppm. We derive a corresponding 2σ upper limit on the geometric albedo of Ag < 0.55 once decontaminated from the thermal emission measured by Spitzer at 4.5 µm. CHEOPS’s photometric performance enables, for the first time, the detection of individual occultations of this super-Earth in the visible and identifies short-timescale photometric corrugations likely induced by stellar granulation. We also find a clear 47.3-day sinusoidal pattern in the time-dependent occultation depths that we are unable to relate to stellar noise, nor instrumental systematics, but whose planetary...
Monthly Notices of the Royal Astronomical Society
EBLM J0113+31 is moderately bright (V=10.1), metal-poor ([Fe/H] ≈−0.3) G0V star with a much faint... more EBLM J0113+31 is moderately bright (V=10.1), metal-poor ([Fe/H] ≈−0.3) G0V star with a much fainter M dwarf companion on a wide, eccentric orbit (=14.3 d). We have used near-infrared spectroscopy obtained with the SPIRou spectrograph to measure the semi-amplitude of the M dwarf’s spectroscopic orbit, and high-precision photometry of the eclipse and transit from the CHEOPS and TESS space missions to measure the geometry of this binary system. From the combined analysis of these data together with previously published observations we obtain the following model-independent masses and radii: M1 = 1.029 ± 0.025M⊙, M2 = 0.197 ± 0.003M⊙, R1 = 1.417 ± 0.014R⊙, R2 = 0.215 ± 0.002R⊙. Using R1 and the parallax from Gaia EDR3 we find that this star’s angular diameter is θ = 0.0745 ± 0.0007 mas. The apparent bolometric flux of the G0V star corrected for both extinction and the contribution from the M dwarf (<0.2 per cent) is mathcalFoplus,0=(2.62pm0.05)times10−9{\mathcal {F}}_{\oplus ,0} = (2.62\pm 0.05)\times 10^{-9}mathcalFoplus,0=(2.62pm0.05)times10−9 erg cm−2...
VizieR Online Data Catalog (other), Jun 1, 2021
VizieR Online Data Catalog, Sep 1, 2020
Astronomy & Astrophysics, 2022
Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as dete... more Here we report large-amplitude transit timing variations (TTVs) for AU Microcopii b and c as detected in combined TESS (2018, 2020) and CHEOPS (2020, 2021) transit observations. AU Mic is a young planetary system with a debris disk and two transiting warm Neptunes. A TTV on the order of several minutes was previously reported for AU Mic b, which was suggested to be an outcome of mutual perturbations between the planets in the system. In 2021, we observed AU Mic b (five transits) and c (three transits) with the CHEOPS space telescope to follow-up the TTV of AU Mic b and possibly detect a TTV for AU Mic c. When analyzing TESS and CHEOPS 2020−2021 measurements together, we find that a prominent TTV emerges with a full span of ≥23 min between the two TTV extrema. Assuming that the period change results from a periodic process –such as mutual perturbations– we demonstrate that the times of transits in the summer of 2022 are expected to be 30−85 min later than predicted by the available l...
Astronomy & Astrophysics, 2021
Context. Hot subdwarfs experienced strong mass loss on the red giant branch (RGB) and are now hot... more Context. Hot subdwarfs experienced strong mass loss on the red giant branch (RGB) and are now hot and small He-burning objects. These stars constitute excellent opportunities for addressing the question of the evolution of exoplanetary systems directly after the RGB phase of evolution. Aims. In this project we aim to perform a transit survey in all available light curves of hot subdwarfs from space-based telescopes (Kepler, K2, TESS, and CHEOPS) with our custom-made pipeline SHERLOCK in order to determine the occurrence rate of planets around these stars as a function of orbital period and planetary radius. We also aim to determine whether planets that were previously engulfed in the envelope of their red giant host star can survive, even partially, as a planetary remnant. Methods. For this first paper, we performed injection-and-recovery tests of synthetic transits for a selection of representative Kepler, K2, and TESS light curves to determine which transiting bodies in terms of o...
CHEOPS (CHaracterising ExOPlanet Satellite) is the first ESA Small Mission as part of the ESA Cos... more CHEOPS (CHaracterising ExOPlanet Satellite) is the first ESA Small Mission as part of the ESA Cosmic Vision program 2015-2025 and it is planned launch readiness end of 2017. The mission lead is performed in a partnership between Switzerland, led by the University of Bern, and the European Space Agency with important contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS mission will be the first space telescope dedicated to search for exoplanetary transits on bright stars already known to host planets by performing ultrahigh precision photometry on bright starts whose mass has been already estimated through spectroscopic surveys on ground based observations. The number of exoplanets in the mass range 1-30 MEarth for which both mass and radius are known with a good precision is extremely limited also considering the last two decades of high-precision radial velocity measurement campaigns and the highly success...
Presentamos nuestros resultados sobre la formación de planetas gigantes dentro del marco del meca... more Presentamos nuestros resultados sobre la formación de planetas gigantes dentro del marco del mecanismo de inestabilidad nucleada. Consideramos el régimen de crecimiento oligárquico para el núcleo sólido y una reducción en la opacidad de los granos. Bajo estas suposiciones, la formación de planetas gigantes in situ se puede alcanzar en una escala de tiempo más corta que la duración de vida de discos protoplanetarios.
Context. A large sample of long-period giant planets has been discovered thanks to long-term radi... more Context. A large sample of long-period giant planets has been discovered thanks to long-term radial velocity surveys, but only a few dozen of these planets have a precise radius measurement. Transiting gas giants are crucial targets for the study of atmospheric composition across a wide range of equilibrium temperatures and, more importantly, for shedding light on the formation and evolution of planetary systems. Indeed, compared to hot Jupiters, the atmospheric properties and orbital parameters of cooler gas giants are unaltered by intense stellar irradiation and tidal effects. Aims. We aim to identify long-period planets in the Transiting Exoplanet Survey Satellite (TESS) data as single or duo-transit events. Our goal is to solve the orbital periods of TESS duo-transit candidates with the use of additional space-based photometric observations and to collect follow-up spectroscopic observations in order to confirm the planetary nature and measure the mass of the candidates. Methods. We use the CHaracterising ExOPlanet Satellite (CHEOPS) to observe the highest-probability period aliases in order to discard or confirm a transit event at a given period. Once a period is confirmed, we jointly model the TESS and CHEOPS light curves along with the radial velocity datasets to measure the orbital parameters of the system and obtain precise mass and radius measurements. Results. We report the discovery of a long-period transiting Neptune-mass planet orbiting the G7-type star TOI-5678. Our spectroscopic analysis shows that TOI-5678 is a star with a solar metallicity. The TESS light curve of TOI-5678 presents two transit events separated by almost two years. In addition, CHEOPS observed the target as part of its Guaranteed Time Observation program. After four non-detections corresponding to possible periods, CHEOPS detected a transit event matching a unique period alias. Follow-up radial velocity observations were carried out with the ground-based high-resolution spectrographs CORALIE and HARPS. Joint modeling reveals that TOI-5678 hosts a 47.73 day period planet, and we measure an orbital eccentricity consistent with zero at 2σ. The planet TOI-5678 b has a mass of 20 ± 4 Earth masses (M ⊕) and a radius of 4.91 ± 0.08 R ⊕. Using interior structure modeling, we find that TOI-5678 b is composed of a low-mass core surrounded by a large H/He layer with a mass of 3.2 +1.7 −1.3 M ⊕. Conclusions. TOI-5678 b is part of a growing sample of well-characterized transiting gas giants receiving moderate amounts of stellar insolation (11 S ⊕). Precise density measurement gives us insight into their interior composition, and the objects orbiting bright stars are suitable targets to study the atmospheric composition of cooler gas giants. Key words. planets and satellites: detection-planets and satellites: individual: TOI-5678-planets and satellites: gaseous planetsmethods: data analysis ⋆ Full Table 2 and reduced CHEOPS and HARPS data are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr
Astronomy & Astrophysics, 2021
Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 ma... more Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 mag) star HD 108236 (also known as TOI-1233) was recently reported on the basis of TESS and ground-based light curves. Aims. We perform a first characterisation of the HD 108236 planetary system through high-precision CHEOPS photometry and improve the transit ephemerides and system parameters. Methods. We characterise the host star through spectroscopic analysis and derive the radius with the infrared flux method. We constrain the stellar mass and age by combining the results obtained from two sets of stellar evolutionary tracks. We analyse the available TESS light curves and one CHEOPS transit light curve for each known planet in the system. Results. We find that HD 108236 is a Sun-like star with R⋆ = 0.877 ± 0.008 R⊙, M⋆ = 0.869−0.048+0.050 M⊙, and an age of 6.7−5.1+4.0 Gyr. We report the serendipitous detection of an additional planet, HD 108236 f, in one of the CHEOPS light curves. For...
Giant planet formation process is still not completely understood. The current most accepted para... more Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the solar system’s giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks ’ lifetimes, especially for the cases of Uranus and Neptune. In the context of this model, and considering a recently proposed primordial solar system orbital structure, we performed numerical calculations of giant planet formation. Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30-100 meter sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario. The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.
Monthly Notices of the Royal Astronomical Society, 2021
CHEOPS (CHaracterising ExOPlanet Satellite) is an ESA S-class mission that observes bright stars ... more CHEOPS (CHaracterising ExOPlanet Satellite) is an ESA S-class mission that observes bright stars at high cadence from low-Earth orbit. The main aim of the mission is to characterize exoplanets that transit nearby stars using ultrahigh precision photometry. Here, we report the analysis of transits observed by CHEOPS during its Early Science observing programme for four well-known exoplanets: GJ 436 b, HD 106315 b, HD 97658 b, and GJ 1132 b. The analysis is done using pycheops, an open-source software package we have developed to easily and efficiently analyse CHEOPS light-curve data using state-of-the-art techniques that are fully described herein. We show that the precision of the transit parameters measured using CHEOPS is comparable to that from larger space telescopes such as Spitzer Space Telescope and Kepler. We use the updated planet parameters from our analysis to derive new constraints on the internal structure of these four exoplanets.
Proceedings of the International Astronomical Union, 2010
Photometric observations of transits can be used to derive physical and orbital parameters of the... more Photometric observations of transits can be used to derive physical and orbital parameters of the system, like the planetary and stellar radius, orbital inclination and mean density of the star. Furthermore, monitoring possible periodic variations in transit timing of planets is important, since small changes can be caused by the presence of other planets or moons in the system. On the other hand, long term changes in the transit length can be due to the orbital precession of the planets. For these reasons we started an observational program dedicated to observe transits of known exoplanets with the aim of contributing to a better understanding of these planetary systems. In this work we present our first results obtained using the observational facilities in Argentina including the 2.15 telescope at CASLEO.
In the frame of the core instability model, we present calculations of in situ giant planet forma... more In the frame of the core instability model, we present calculations of in situ giant planet formation introducing the oligarchic growth regime of planetesimals as the time dependent core accretion rate. As giant planets are mainly composed of gas, to obtain a self consistent oligarchic core accretion rate, an accurate model of its atmosphere's structure has to be considered in the calculation of the effective cross section for planetesimal capture. We made several simulations of the formation of a Jupiter like object. Including the gas drag effect of the protoplanet's atmosphere produces an important enhancement on its effective capture radius leading to a timescale reduction but duplicating the final mass of solids accreted. FULL TEXT IN SPANISH