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

Abstract

We report the discovery and characterization of the transiting extrasolar planet TOI-1710b. 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-1710b is found to be a massive warm super-Neptune ($M_{\mathrm{p}}=28.3\pm 4.7{\mathrm{M}}_{\mathrm{Earth}}$ and $R_{\mathrm{p}}=5.34\pm 0.11{\mathrm{R}}_{\mathrm{Earth}}$) orbiting a G5V dwarf star ($T_{\mathrm{eff}}=5665\pm 55\mathrm{K}$) 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 $P_{\mathrm{rot}}=22.5\pm 2.0\mathrm{days}$ and it has a low Keplerian semi-amplitude $K=6.4\pm 1.0\mathrm{m}{\mathrm{s}}^{-1}$; 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-1710b 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.

18 pages, 16 figures, 5 tables, A&A in press