TOI-5108 b and TOI 5786 b: Two transiting sub-Saturns detected and characterized with TESS, MaHPS and SOPHIE
Luis Thomas, Guillaume H’ebrard, Hanna Kellermann, Judith Korth, Neda Heidari, Thierry Forveille, S’ergio G. Sousa, Laura Sch"oller, Arno Riffeser, Claus G"ossl, Juan Serrano Bell, Flavien Kiefer, Nathan Hara, Frank Grupp, Juliana Ehrhardt, Felipe Murgas, Karen A. Collins, Allyson Bieryla, Hannu Parviainen, Alexandr A. Belinski, Emma Esparza-Borges, David R. Ciardi, Catherine A. Clark, Akihiko Fukui, Emily A. Gilbert, Ulrich Hopp, Kai Ikuta, Jon M. Jenkins, David W. Latham, Norio Narita, Louise D. Nielsen, Samuel N. Quinn, Enric Palle, Jan-Niklas Pippert, Alex S. Polanski, Christoph Ries, Michael Schmidt, Richard P. Schwarz, Sara Seager, Ivan A. Strakhov, Stephanie Striegel, Julian C. van Eyken, Noriharu Watanabe, Cristilyn N. Watkins, Joshua N. Winn, Carl Ziegler, Raphael Z"oller
arXiv:2501.03803v1 Announce Type: new
Abstract: We report the discovery and characterization of two sub-Saturns from the Transiting Exoplanet Survey Satellite (textit{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 with the radial velocity measurements from MaHPS and SOPHIE we measure precise radii and masses for both planets. TOI-5108 b is a sub-Saturn with a radius of $6.6 pm 0.1$ $R_oplus$ and a mass of $32 pm 5$ $M_oplus$. TOI-5786 b is similar to Saturn with a radius of $8.54 pm 0.13$ $R_oplus$ and a mass of $73 pm 9$ $M_oplus$. 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 inside the bounds of the Neptune desert while TOI-5786 b is right above the upper edge. We estimate hydrogen-helium envelope mass fractions of $38 %$ for TOI-5108 b and $74 % $ for TOI-5786 b. However, using a model for the interior structure that includes tidal effects the envelope fraction of TOI-5108 b could be much lower ($sim 20,%$) depending on the obliquity. We estimate mass-loss rates between 1.0 * $10^9$ g/s and 9.8 * $10^9$ g/s for TOI-5108 b and between 3.6 * $10^8$ g/s and 3.5 * $10^9$ g/s for TOI-5786 b. Given their masses, this means that both planets are stable against photoevaporation. We also detect 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 $3.83 pm 0.16$ $R_oplus$. Using our RV data and photodynamical modeling, we are able to provide a 3-$sigma$ upper limit of 26.5 $M_oplus$ for the mass of the potential inner companion to TOI-5786 b.arXiv:2501.03803v1 Announce Type: new
Abstract: We report the discovery and characterization of two sub-Saturns from the Transiting Exoplanet Survey Satellite (textit{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 with the radial velocity measurements from MaHPS and SOPHIE we measure precise radii and masses for both planets. TOI-5108 b is a sub-Saturn with a radius of $6.6 pm 0.1$ $R_oplus$ and a mass of $32 pm 5$ $M_oplus$. TOI-5786 b is similar to Saturn with a radius of $8.54 pm 0.13$ $R_oplus$ and a mass of $73 pm 9$ $M_oplus$. 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 inside the bounds of the Neptune desert while TOI-5786 b is right above the upper edge. We estimate hydrogen-helium envelope mass fractions of $38 %$ for TOI-5108 b and $74 % $ for TOI-5786 b. However, using a model for the interior structure that includes tidal effects the envelope fraction of TOI-5108 b could be much lower ($sim 20,%$) depending on the obliquity. We estimate mass-loss rates between 1.0 * $10^9$ g/s and 9.8 * $10^9$ g/s for TOI-5108 b and between 3.6 * $10^8$ g/s and 3.5 * $10^9$ g/s for TOI-5786 b. Given their masses, this means that both planets are stable against photoevaporation. We also detect 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 $3.83 pm 0.16$ $R_oplus$. Using our RV data and photodynamical modeling, we are able to provide a 3-$sigma$ upper limit of 26.5 $M_oplus$ for the mass of the potential inner companion to TOI-5786 b.

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