TOI-132 b: A short-period planet in the Neptune desert transiting a V=11.3 G-type star

The Neptune desert is a feature seen in the radius-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here, we report the Transiting Exoplanet Survey Satellite (TESS) discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC 8003-1117-1 (TOI-132). TESS photometry shows transit-like dips at the level of similar to 1400 ppm occurring every similar to 2.11 d. High-precision radial velocity follow-up with High Accuracy Radial Velocity Planet Searcher confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of 11.38(-0.85)(+0.84) m s(-1), which, when combined with the stellar mass of 0.97 +/- 0.06 M-circle dot, provides a planetary mass of 22.40(-1.92)(+1.90) M-circle plus. Modelling the TESS light curve returns a planet radius of 3.42(-0.14)(+0.13) R-circle plus , and therefore the planet bulk density is found to be 3.08(-0.46)(+0.44) g cm(-3). Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3(-2.3)(+1.2) percent. TOI-132 b is a TESS Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding of the Neptune desert

Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops

peer reviewedHIP 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 50 d, opening the door for the atmospheric characterization of warm (Teq < 750 K) sub-Neptunes

Caractérisation de l'activité stellaire des naines M par spectroscopie de haute précision dans l'optique et le proche infrarouge pour la recherche de planètes de faible masse

Les naines M sont devenues des cibles privilégiées pour la détection et la caractérisation des exoplanètes. Leur faible masse en fait des cibles idéales pour effectuer des relevés de vitesse radiale (VR) puisque, pour une masse donnée, la force gravitationnelle de la planète sera plus importante que pour les étoiles semblables au Soleil. Cependant, les naines M sont connues pour être des étoiles magnétiquement actives. L'activité stellaire est actuellement l'une des principales limites à la détection des planètes de faible masse, car elle induit des variations quasi-périodiques du VR de l'ordre de quelques mètres par seconde. Cette thèse vise à étudier l'activité stellaire des naines M en utilisant la spectroscopie de haute précision dans les domaines optique et proche infrarouge afin d'améliorer la détection des planètes de faible masse. Dans le domaine du proche infrarouge, j'ai utilisé la spectroscopie de haute précision et la spectropolarimétrie de SPIRou, qui est monté sur le télescope Canada-France-Hawaii. Le calcul de la vitesse radiale des naines M est encore difficile dans le proche infrarouge en raison de la grande quantité de raies telluriques dans leurs spectres. D'une part, j'ai travaillé en étroite collaboration avec l'équipe du système de réduction des données et j'ai effectué plusieurs tests pour mesurer l'impact de la sélection des masques dans le calcul du CCF. D'autre part, j'ai développé des outils informatiques pour obtenir des indicateurs d'activité à partir des spectres SPIRou basés sur la forme du CCF et sur la largeur pseudo-équivalente des lignes spectrales dans le domaine SPIRou. J'ai testé leurs performances sur un échantillon de naines M. Dans le domaine optique, j'ai travaillé avec le spectrographe SOPHIE situé à l'Observatoire de Haute Provence. Une douzaine d'étoiles de type M sont suivies quasi-simultanément avec SOPHIE et SPIRou afin d'améliorer la caractérisation de la variation de l'activité stellaire dans l'optique et le proche infrarouge. J'ai utilisé l'algorithme de template-matching NAIRA pour calculer les vitesses radiales de SOPHIE et les indicateurs d'activité. J'ai dirigé la première publication d'une cible SOPHIE+SPIRou, la naine M Gl 205, sur laquelle j'ai effectué une analyse approfondie du signal d'activité stellaire dans les deux domaines en utilisant la technique du processus gaussien. J'ai analysé les VRs et les indicateurs d'activité de l'échantillon complet SOPHIE+SPIRou pour rechercher des périodicités liées à l'activité stellaire et aux planètes. J'ai identifié deux cibles intéressantes avec des signaux compatibles dans l'optique et le proche infrarouge. Une deuxième publication est en préparation avec une analyse détaillée de l'activité stellaire et un possible signal KeplerienneM dwarfs have become favorite targets for exoplanet detection and characterization. Their low mass makes them ideal to perform radial velocity (RV) surveys since, for a given planet's mass, the planet's gravitational pull will be greater than for Sun-like stars. However, M dwarfs are known to be magnetically active stars. Stellar activity is currently one of the main limitations to detecting low-mass planets as it induces quasi-periodic RV variations of the order of a few meters per second. This thesis aims to characterize and study the stellar activity of M dwarfs using high-precision spectroscopy in the optical and near-infrared (nIR) domains to improve the detection of low-mass planets. In the near-infrared domain, I used high-precision spectroscopy and spectropolarimetry from SPIRou, which is mounted at the Canada-France-Hawaii telescope. The computation of the precise radial velocity is challenging in the near-infrared due to the high amount of telluric lines in their spectra. On the one hand, I worked closely with the Data Reduction System team and performed several tests to measure the impact of the mask selection in the CCF computation. On the other, I developed computational tools to obtain activity indicators from SPIRou spectra based on the CCF shape and on the pseudo-equivalent width of spectral lines in the SPIRou domain. I tested their performances in a sample of M dwarfs. In the optical domain, I worked with the SOPHIE spectrograph located at the observatoire de Haute Provence. A dozen of SP3 targets are being monitored quasi-simultaneously with SOPHIE and SPIRou to improve the characterization of the stellar activity jitter in the optical and near-infrared. I used the template-matching algorithm NAIRA to compute the SOPHIE RVs and activity indicators of the SP3 targets. I led the first publication of a SOPHIE+SPIRou target, the early M dwarf Gl 205, on which a performed an extensive analysis of the stellar activity signal in both domains using the data-driven technique of Gaussian Process. I analyzed the RVs and activity indicators of the SOPHIE+SPIRou complete sample to look for periodicities related to stellar activity and planets. I identified two interesting targets with compatible signals in the optical and nIR. A second publication is under preparation with the detailed analysis of the stellar activity and one possible Keplerian

Planet Hunters TESS. V. A Planetary System Around a Binary Star, Including a Mini-Neptune in the Habitable Zone

International audienceWe report on the discovery and validation of a transiting long-period mini-Neptune orbiting a bright ( V = 9.0 mag) G dwarf (TOI 4633; R = 1.05 R ⊙ , M = 1.10 M ⊙ ). The planet was identified in data from the Transiting Exoplanet Survey Satellite by citizen scientists taking part in the Planet Hunters TESS project. Modelling of the transit events yields an orbital period of 271.9445 ± 0.0040 days and radius of 3.2 ± 0.20 R ⊕ . The Earth-like orbital period and an incident flux of 1.56 − 0.16 + 0.20 F ⊕ places it in the optimistic habitable zone around the star. Doppler spectroscopy of the system allowed us to place an upper mass limit on the transiting planet and revealed a non-transiting planet candidate in the system with a period of 34.15 ± 0.15 days. Furthermore, the combination of archival data dating back to 1905 with new high angular resolution imaging revealed a stellar companion orbiting the primary star with an orbital period of around 230 yr and an eccentricity of about 0.9. The long period of the transiting planet, combined with the high eccentricity and close approach of the companion star makes this a valuable system for testing the formation and stability of planets in binary systems

An ultrahot Neptune in the Neptune desert

About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet1,2. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite3 revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0+2.7−2.9% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (Vmag = 9.8).<br