The GAPS programme at TNG. LVII. TOI-5076b: A warm sub-Neptune planet orbiting a thin-to-thick-disk transition star in a wide binary system

Abstract

Aims: We report the confirmation of a new transiting exoplanet orbiting the star TOI-5076. <BR /> Methods: We present our vetting procedure and follow-up observations which led to the confirmation of the exoplanet TOI-5076b. In particular, we employed high-precision TESS photometry, high-angular-resolution imaging from several telescopes, and high-precision radial velocities from HARPS-N. <BR /> Results: From the HARPS-N spectroscopy, we determined the spectroscopic parameters of the host star: T<SUB>eff</SUB> = (5070±143) K, log 𝑔 = (4.6±0.3), [Fe/H] = (+0.20±0.08), and [α/Fe] = 0.05±0.06. The transiting planet is a warm sub-Neptune with a mass m<SUB>p</SUB> = (16±2) M<SUB>⊙</SUB>, a radius r<SUB>p</SUB> =(3.2±0.l) R<SUB>⊙</SUB> yielding a density ρ<SUB>p</SUB> = (2.8±0.5) g cm<SUP>−3</SUP>. It revolves around its star approximately every 23.445 days. <BR /> Conclusions: The host star is a metal-rich, K2V dwarf, located at about 82 pc from the Sun with a radius of R<SUB>⋆</SUB> = (0.78±0.01) R<SUB>⊙</SUB> and a mass of M<SUB>⋆</SUB> = (0.80±0.07) M<SUB>⊙</SUB>. It forms a common proper motion pair with an M-dwarf companion star located at a projected separation of 2178 au. The chemical analysis of the host-star and the Galactic-space velocities indicate that TOI-5076 belongs to the old population of thin-to-thick-disk transition stars. The density of TOI-5076b suggests the presence of a large fraction by volume of volatiles overlying a massive core. We found that a circular orbit solution is marginally favored with respect to an eccentric orbit solution for TOI-5076b. <P />Full Tables 2 and 3 are available at the CDS via anonymous ftp to <A href="https://cdsarc.cds.unistra.fr/">cdsarc.cds.unistra.fr</A> (ftp://130.79.128.5) or via <A href="https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/687/A226">https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/687/A226</A>