2022, Nardiello, D., Malavolta, L., Desidera, S., Baratella, M., D’Orazi, V., Messina, S., Biazzo, K., Benatti, S., Damasso, M., Rajpaul, V.M., Bonomo, A.S., Capuzzo Dolcetta, R., Mallonn, M., Cale, B., Plavchan, P., El Mufti, M., Bignamini, A., Borsa, F., Carleo, I., Claudi, R., Covino, E., Lanza, A.F., Maldonado, J., Mancini, L., Micela, G., Molinari, E., Pinamonti, M., Piotto, G., Poretti, E., Scandariato, G., Sozzetti, A., Andreuzzi, G., Boschin, W., Cosentino, R., Fiorenzano, A.F.M., Harutyunyan, A., Knapic, C., Pedani, M., Affer, L., Maggio, A., Rainer, M.

Context. Great strides have been made in recent years in the understanding of the mechanisms involved in the formation and evolution of planetary systems. Despite this, many observational findings have not yet been corroborated by astrophysical explanations. A fine contribution to the study of planetary formation processes comes from the study of young, low-mass planets, with short orbital periods (.100 days). In the last three years, the NASA/TESS satellite has identified many planets of this kind and their characterization is clearly necessary in order to understand how they formed and evolved. Aims. Within the framework of the Global Architecture of Planetary System (GAPS) project, we performed a validation and characterization (radius and mass) of the ultra-short period planet TOI-1807 b, which orbits its young host star BD+39 2643 (∼300 Myr) in only 13 h. This is the youngest ultra-short period planet discovered so far. Methods. Thanks to a joint modeling of the stellar activity and planetary signals in the TESS light curve and in new HARPS-N radial-velocity measurements, combined with accurate estimation of stellar parameters, we validated the planetary nature of TOI-1807 b and measured its orbital and physical parameters. Results. By using astrometric, photometric, and spectroscopic observations, we found that BD+39 2643 is a young, active K dwarf star and a member of a 300 ± 80 Myr old moving group. Furthermore, it rotates in Prot = 8.8 ± 0.1 days. This star hosts an ultra-short period planet, exhibiting an orbital period of only Pb = 0.54937 ± 0.00001 days. Thanks to the exquisite photometric and spectroscopic series, along with the accurate information on its stellar activity, we measured both the radius and the mass of TOI-1807 b with high precision, obtaining RP,b = 1.37 ± 0.09 R⊕ and MP,b = 2.57 ± 0.50 M⊕. These planet parameters correspond to a rocky planet with an Earth-like density (ρb = 1.0 ± 0.3 ρ⊕) and no extended H/He envelope. From the analysis of the age-RP distribution for planets with well measured ages, we inferred that TOI-1807 b may have already lost a large part of its atmosphere over the course of its 300 Myr lifetime.

2022, Zhang, R., Lucatello, S., Bragaglia, A., Alonso-Santiago, J., Andreuzzi, G., Casali, G., Carrera, R., Carretta, E., D’Orazi, V., Frasca, A., Fu, X., Magrini, L., Minchev, I., Origlia, L., Spina, L., Vallenari, A.

Context. Exploring the Galactic chemical evolution and enrichment scenarios with open clusters (OCs) allows us to understand the history of the Milky Way disk. High-resolution spectra of OCs are a crucial tool, as they provide precise chemical information, to combine with precise distances and ages. Aims. The aim of the Stellar Population Astrophysics (SPA) project is to derive homogeneous and accurate comprehensive chemical characterization of a number of poorly studied OCs. Methods. Using the HARPS-N echelle spectrograph at the Telescopio Nazionale Galileo (TNG), we obtained high-resolution spectra of giant stars in 18 OCs, 16 of which are chemically characterized for the first time, and two of which are well studied for comparison. The OCs in this sample have ages from a few tens of Myr to 4 Gyr, with a prevalence of young clusters. We already presented the radial velocities and atmospheric parameters for them in a previous SPA paper. Here, we present results for the α-elements O, Mg, Si, Ca and Ti, and the light elements Na and Al, all determined by the equivalent width method. We also measured Li abundance through the synthesis method. Results. We discuss the behaviors of lithium, sodium and aluminum in the context of stellar evolution. For Na and Al, we compare our findings with models to investigate their behaviors as a function of mass, suggesting that Na mixing to the surface might start in masses as low as 2 M·. We study the radial, vertical, and age trends for the measured abundance ratios in a sample that combines our results and recent literature for OCs, finding significant (positive) gradients only for [Mg/Fe] and [Ca/Fe] in all cases. Finally, we compare O and Mg in the combined sample with chemo-dynamical models, finding a good agreement for intermediate-Age and old clusters. There is a sharp increase in the abundance ratios measured among very young clusters (age < 300 Myr), accompanied by a poorer fit with the models for O and Mg, likely related to the inadequacy of traditional model atmospheres and methods in the derivation of atmospheric parameters and abundance ratios for stars of such young ages.