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 ($M_{\rm p}=28.3:\pm:4.7:{\rm M}{\rm Earth}$and$R{\rm p}=5.34:\pm:0.11:{\rm R}{\rm Earth}$) orbiting a G5V dwarf star ($T_{\mathrm{e}\mathrm{f}\mathrm{f}}=5665\pm 55\mathrm{K}$) on a nearly circular 24.3-day orbit ($e=0.16\pm 0.08$). The orbital period of this planet is close to the estimated rotation period of its host star $P{\rm rot}=22.5\pm2.0~$\mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}$$andithasalowKepleriansemi-amplitude$K=6.4\pm1.0~$\mathrm{m}{\mathrm{s}}^{-1}$$; we thus performed additional analyses to show the robustness of the retrieved planetary parameters. With a low bulk density of $1.03\pm 0.23\mathrm{g}\mathrm{c}{\mathrm{m}}^{-3}$ 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.