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. 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 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-circle plus and R-p = 5.34 +/- 0.11 R-circle plus) orbiting a G5V dwarf star (T-eff = 5665 +/- 55 K) 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.