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

• Published in: Astronomy and astrophysics (Berlin) Vol. 687; p. A226
• Main Authors: Montalto, M., Greco, N., Biazzo, K., Desidera, S., Andreuzzi, G., Bieryla, A., Bignamini, A., Bonomo, A. S., Briceño, C., Cabona, L., Cosentino, R., Damasso, M., Fiorenzano, A., Fong, W., Goeke, B., Hesse, K. M., Kostov, V. B., Lanza, A. F., Latham, D. W., Law, N., Mancini, L., Maggio, A., Molinaro, M., Mann, A. W., Mantovan, G., Naponiello, L., Nardiello, D., Nascimbeni, V., Pagano, I., Pedani, M., Safonov, B. S., Scandariato, G., Seager, S., Singh, V., Sozzetti, A., Strakhov, I. A., Winn, J. N., Ziegler, C., Zingales, T.
• Format: Journal Article
• Language: English
• Published: 16.07.2024
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/202349082

Aims . We report the confirmation of a new transiting exoplanet orbiting the star TOI-5076. 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. Results . From the HARPS-N spectroscopy, we determined the spectroscopic parameters of the host star: T eff = (5070±143) K, log = (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 p = (16±2) M ⊙ , a radius r p =(3.2±0.l) R ⊙ yielding a density ρ p = (2.8±0.5) g cm −3 . It revolves around its star approximately every 23.445 days. Conclusions . The host star is a metal-rich, K2V dwarf, located at about 82 pc from the Sun with a radius of R ⋆ = (0.78±0.01) R ⊙ and a mass of M ⋆ = (0.80±0.07) M ⊙ . 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.