A warm super-Neptune around the G-dwarf star TOI-1710 revealed with TESS, SOPHIE, and HARPS-N

We report the discovery and characterization of the transiting extrasolar planet TOI-1710 b. It was first identified as a promising candidate by the Transiting Exoplanet Survey Satellite ( TESS ). Its planetary nature was then established with SOPHIE and HARPS-N spectroscopic observations via the radial-velocity method. The stellar parameters for the host star are derived from the spectra and a joint Markov chain Monte-Carlo (MCMC) adjustment of the spectral energy distribution and evolutionary tracks of TOI-1710. A joint MCMC analysis of the TESS light curve and the radial-velocity evolution allows us to determine the planetary system properties. From our analysis, TOI-1710 b is found to be a massive warm super-Neptune ( M p = 28 . 3 ± 4 . 7 M ⊕ and R p = 5 . 34 ± 0 . 11 R ⊕ ) orbiting a G5V dwarf star ( T e ff = 5665 ± 55K) on a nearly circular 24.3-day orbit ( e = 0 . 16 ± 0 . 08). The orbital period of this planet is close to the estimated rotation period of its host star P rot = 22 . 5 ± 2 . 0 days and it has a low Keplerian semi-amplitude K = 6 . 4 ± 1 . 0 m s − 1 ; we thus performed additional analyses to show the robustness of the retrieved planetary parameters. With a low bulk density of 1 . 03 ± 0 . 23 g cm − 3 and orbiting a bright host star ( J = 8 . 3, V = 9 . 6), TOI-1710 b is one of the best targets in this mass-radius range (near the Neptunian desert) for atmospheric characterization via transmission spectroscopy, a key measurement in constraining planet formation and evolutionary models of sub-Jovian planets.