Search

Despite the discovery of thousands of exoplanets, the mechanisms of planet formation and evolution have not been well tested with observations, mainly because the lack of a complete photometric and spectroscopic characterization of young planets, which presents a big challenge due to the high stellar activity of young stars. By determining the masses of young exoplanets, we can establish their composition, and investigate their evolution with age. For these observations, we can deduce if they were formed without gas (rocky planets) from their origin, or if they are born as small gaseous planets that lose their atmosphere rapidly (~tens of Myr) by photoevaporation (Murray-Clay et al. 2019) or slowly (~1 Gyr) by core-powered mass loss (Ginzburg et al. 2018). HD63433 is a very bright and fast rotating (6.46 days) solar-type star of the young (~400Myr) Ursa Major moving group hosting two transiting mini-Neptune-size exoplanets (Mann et al. 2020) with orbital periods of 7.11 (HD63433 b) and 20.55 (HD63433 c) days. We have collected 150 Radial Velocity (RV) measurements of HD63433 with CARMENES spectrograph over 1.4 years to determine the mass of the planets (Mallorquín et al. 2022, in prep). We have jointly modeled the transits, the keplerian planetary signal, and stellar activity with Gaussian Processes combining the TESS photometry and the CARMENES RV dataset. Our results reveal that the outer planet is detected in the CARMENES time series with an amplitude of 4.1+-1.0 m/s at the level of 4-sigma, which correspond to an absolute mass of Mp=17.4+-4.3 mass of the Earth for HD63433 c, making it the smallest planet with a robust mass determination at young ages. We report an upper limit of Mp

TOI 1246 is one of only eight four-planet systems with measured masses and radii for all four planets. TESS observed this moderately bright K dwarf (V=11.6, K=9.9) for 12 sectors, and found four transiting planets. We collected 90 RV observations with Keck/HIRES and TNG/HARPS-N, many of which were contemporaneous with TESS photometry. We refit the photometry to refine planet radii, measure masses for all four planets, and find a surprising range of masses and densities. This system is brighter 93% of other four planet systems, and is a particularly interesting testing ground for mass loss and formation hypotheses due to the high planet multiplicity and varied planet masses., {"references":["Tamayo, Daniel et al. (2020), arXiv:2007.06521"]}

Dynamical histories of planetary systems, as well as atmospheric evolution of highly irradiated planets, can be studied by characterizing the ultra-short-period planet population, which the TESS mission is particularly well suited to discover. Here, we report on the follow-up of a transit signal detected in the TESS sector 19 photometric time series of the M3.0 V star TOI-1685. We confirm the planetary nature of the transit signal, which has a period of Pb = 0.6691403+0.0000023-0.0000021 d, using precise radial velocity measurements taken with the CARMENES spectrograph. From the joint photometry and radial velocity analysis, we estimate the following parameters for TOI-1685 b: a mass of Mb = 3.78+0.63- 0.63 M⊕, a radius of Rb = 1.70+0.07- 0.07 R⊕, which together result in a bulk density of ρb = 4.21+0.95-0.82 g/cm3, and an equilibrium temperature of Teq = 1069 +16-16 K. TOI-1685 b is the least dense ultra-short period planet around an M dwarf known to date. TOI-1685 b is also one of the hottest transiting super-Earth planets with accurate dynamical mass measurements, which makes it a particularly attractive target for thermal emission spectroscopy. Additionally, we report with moderate evidence a further non-transiting planet candidate in the system, TOI-1685[c], with an orbital period of Pc = 9.02+0.10- 0.12 d., {"references":["Espinoza et al. 2019, adsurl: https://ui.adsabs.harvard.edu/abs/2019MNRAS.490.2262E","Zeng et al. 2019, adsurl:https://ui.adsabs.harvard.edu/abs/2019PNAS..116.9723Z","Zeng et al. 2016, adsurl: http://adsabs.harvard.edu/abs/2016ApJ...819..127Z","Southworth, J. 2011, adsurl: http://adsabs.harvard.edu/abs/2011MNRAS.417.2166S","Martínez-Rodríguez et al. 2019, adsurl: https://ui.adsabs.harvard.edu/abs/2019ApJ...887..261M"]}

The thermal emission received from a planet is a key to characterize the physical and chemical properties of its atmosphere. The spectral resolution, and therefore the spectral characterization that we can achieve for extrasolar planets is unfortunately very limited in particular for terrestrial planets. In this thesis, we study the possibility to characterize an Earth-like exoplanet by the analysis of the broadband infrared emission variability. The apparent thermal emission is indeed modulated by the seasons, the rotation of the planet, the motion and variability of atmospheric patterns and clouds, the orbital phase, and even the presence of a moon. As a reference case, we have studied the thermal emission of the Earth seen as a distant point-source, as well as the variability and the dependency of the signal on the observation geometry. We have modeled the emission of the Earth using data derived from observations and data produced by a General Circulation Models (GCMs), comparing both types of data in order to validate our simulations.As a second part of our work, we have used the GCM to model Earth-like planets that differ from the Earth by a few parameters such as different rotation rates (including tidally-locked planets), a planetary surface completely covered by ice or water, different obliquities and eccentricities. For all these virtual planets, we have studied the climate derived from the physical properties and the photometric infrared signal associated with them.The last part of the thesis is a preliminary work that no longer consider the bolometric emission but the signal from narrow spectral bands, thanks to a new generation of GCMs. Because each band probes a specific level in the atmosphere, studying how the low resolution spectrum of the planets varies by comparing the photometric variabilities between bands, we can study the dynamics, composition, distribution and evolution of the atmosphere of the planet, which it opens a yet unexplored field for the characterization of exoplanets.; Le signal thermique d'une exoplanète tellurique est une clé pour caractériser les propriétés physiques et chimiques de son atmosphère. La résolution spectrale, et donc la caractérisation spectrale que nous pouvons réaliser des planètes extrasolaires, est malheureusement très limité, en particulier pour les planètes similaires à la Terre. Dans cette thèse, j'ai étudié la possibilité de caractériser des exoplanètes telluriques par l'analyse de la variabilité de son émission infrarouge. L'émission thermique apparente est en effet modulée par les saisons, la rotation de la planète, le mouvement et la variabilité des nuages, la phase orbitale, et aussi par la présence des satellites naturels.Premièrement, nous avons étudié l' émission thermique de la Terre vue en tant que point-source distante, ainsi que la variabilité et la dépendance du signal de la géométrie d'observation. J'ai modélisé l'émission de la Terre à l'aide des données satellitaires et des données produites par des modèles de circulation général (GCMs) du Laboratoire de Météorologie Dynamique de Paris (LMD), en comparant les deux types de données afin de valider les simulations.Pendant la deuxième partie de mon travail, j'ai utilisé des donnés du GCM pour modéliser des planètes telluriques qui diffèrent de la Terre par seulement un ou deux paramètres tels que: la vitesse de rotation (y compris des planètes synchrones), une surface planétaire entièrement recouverte par la glace ou de l'eau, l'obliquité de l'axe de rotation ou l'excentricité de l'orbite. Pour toutes ces planètes virtuelles, j'ai étudié le climat, déduit les propriétés physiques de la planète, et produit et analysé les signaux intégrés associés à différentes géométries d'observation.La dernière partie de la thèse est un travail préliminaire qui consiste en ne plus considérer l'émission bolométrique mais le signal de bandes spectrales étroites, grâce à une nouvelle génération de GCM. Parce que chaque bande explore un niveau spécifique dans l'atmosphère, l'étude de la variation du spectre en comparant les variabilités photométriques entre les bandes, permet d'étudier la dynamique, la composition, la distribution et l'évolution de l'atmosphère de la planète, ce qui ouvre un champ encore inexploré pour la caractérisation des exoplanètes.