Revisiting the warm sub-Saturn TOI-1710b

Abstract

The Transiting Exoplanet Survey Satellite (TESS) provides a continuous suite of new planet candidates that need confirmation and precise mass determination from ground-based observatories. This is the case for the G-type star TOI-1710, which is known to host a transiting sub-Saturn planet (${\mathrm{M}}_{\mathrm{p}}=$28.3$\pm$4.7${\mathrm{M}}_{\oplus }$) in a long-period orbit (P=24.28\,d). Here we combine archival SOPHIE and new and archival HARPS-N radial velocity data with newly available TESS data to refine the planetary parameters of the system and derive a new mass measurement for the transiting planet, taking into account the impact of the stellar activity on the mass measurement. We report for TOI-1710b a radius of ${\mathrm{R}}_{\mathrm{p}}$$=$5.15$\pm$0.12${\mathrm{R}}_{\oplus }$, a mass of ${\mathrm{M}}_{\mathrm{p}}$$=$18.4$\pm$4.5${\mathrm{M}}_{\oplus }$, and a mean bulk density of $\ddot{I}{}_{\mathrm{p}}$$=$0.73$\pm$0.18$\mathrm{g}\mathrm{c}{\mathrm{m}}^{-3}$, which are consistent at 1.2$\ddot{I}ƒ$, 1.5$\ddot{I}ƒ$, and 0.7$\ddot{I}ƒ$, respectively, with previous measurements. Although there is not a significant difference in the final mass measurement, we needed to add a Gaussian process component to successfully fit the radial velocity dataset. This work illustrates that adding more measurements does not necessarily imply a better mass determination in terms of precision, even though they contribute to increasing our full understanding of the system. Furthermore, TOI-1710b joins an intriguing class of planets with radii in the range 4-8 ${\mathrm{R}}_{\oplus }$ that have no counterparts in the Solar System. A large gaseous envelope and a bright host star make TOI-1710b a very suitable candidate for follow-up atmospheric characterization.

Accepted for publication in A&A. 21 pages, 14 figures