Bibcode
Thomas, Luis; Hébrard, Guillaume; Kellermann, Hanna; Korth, Judith; Heidari, Neda; Forveille, Thierry; Sousa, Sérgio G.; Schöller, Laura; Riffeser, Arno; Gössl, Claus; Serrano Bell, Juan; Kiefer, Flavien; Hara, Nathan; Grupp, Frank; Ehrhardt, Juliana; Murgas, Felipe; Collins, Karen A.; Bieryla, Allyson; Parviainen, Hannu; Belinski, Alexandr A.; Esparza-Borges, Emma; Ciardi, David R.; Clark, Catherine A.; Fukui, Akihiko; Gilbert, Emily A.; Hopp, Ulrich; Ikuta, Kai; Jenkins, Jon M.; Latham, David W.; Narita, Norio; Nielsen, Louise D.; Quinn, Samuel N.; Palle, Enric; Pippert, Jan-Niklas; Polanski, Alex S.; Ries, Christoph; Schmidt, Michael; Schwarz, Richard P.; Seager, Sara; Strakhov, Ivan A.; Striegel, Stephanie; van Eyken, Julian C.; Watanabe, Noriharu; Watkins, Cristilyn N.; Winn, Joshua N.; Ziegler, Carl; Zöller, Raphael
Bibliographical reference
Astronomy and Astrophysics
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2
2025
Journal
Citations
5
Refereed citations
3
Description
We report the discovery and characterization of two sub-Saturns from the Transiting Exoplanet Survey Satellite (TESS) using high- resolution spectroscopic observations from the MaHPS spectrograph at the Wendelstein Observatory and the SOPHIE spectrograph at the Haute-Provence Observatory. Combining photometry from TESS, KeplerCam, LCOGT, and MuSCAT2, along with the radial velocity measurements from MaHPS and SOPHIE, we measured precise radii and masses for both planets. TOI-5108 b is a sub-Saturn, with a radius of 6.6 ± 0.1 R⊕ and a mass of 32 ± 5 M⊕. TOI-5786 b is similar to Saturn, with a radius of 8.54 ± 0.13 R⊕ and a mass of 73 ± 9 M⊕. The host star for TOI-5108 b is a moderately bright (Vmag 9.75) G-type star. TOI-5786 is a slightly dimmer (Vmag 10.2) F-type star. Both planets are close to their host stars, with periods of 6.75 days and 12.78 days, respectively. This puts TOI-5108 b just within the bounds of the Neptune desert, while TOI-5786 b is right above the upper edge. We estimated hydrogen-helium (H/He) envelope mass fractions of 38% for TOI-5108 b and 74% for TOI-5786 b. However, when using a model for the interior structure that includes tidal effects, the envelope fraction of TOI-5108 b could be much lower (~20%), depending on the obliquity. We estimated mass-loss rates between 1.0 x 109 g/s and 9.8 x 109 g/s for TOI-5108 b and between 3.6 x 108 g/s and 3.5 x 109 g/s for TOI-5786 b. Given their masses, both planets could be stable against photoevaporation. Furthermore, at these mass-loss rates, there is likely no detectable signal in the metastable helium triplet with the James Webb Space Telescope (JWST). We also detected a transit signal for a second planet candidate in the TESS data of TOI-5786, with a period of 6.998 days and a radius of 3.83 ± 0.16 R⊕. Using our RV data and photodynamical modeling, we were able to provide a 3-σ upper limit of 26.5 M⊕ for the mass of the potential inner companion to TOI-5786 b.
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Exoplanets and Astrobiology
The search for life in the universe has been driven by recent discoveries of planets around other stars (known as exoplanets), becoming one of the most active fields in modern astrophysics. The growing number of new exoplanets discovered in recent years and the recent advance on the study of their atmospheres are not only providing new valuable
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