Stellar population astrophysics (SPA) with the TNG. GIANO-B spectroscopy of red supergiants in Alicante 7 and Alicante 10.

Abstract

The Scutum complex in the inner disk of the Galaxy hosts a number of young clusters and associations of red supergiant stars that are heavily obscured by dust extinction. These stars are important tracers of the recent star formation and chemical enrichment history in the inner Galaxy. Within the SPA Large Programme at the TNG, we secured GIANO-B high-resolution (R=50,000) YJHK spectra of 11 red supergiants toward the Alicante 7 and Alicante 10 associations near the RSGC3 cluster. Taking advantage of the full YJHK spectral coverage of GIANO in a single exposure, we were able to measure several hundreds of atomic and molecular lines that are suitable for chemical abundance determinations. We also measured a prominent diffuse interstellar band at lambda=1317.8 nm (vacuum). This provides an independent reddening estimate. The radial velocities, Gaia proper motions, and extinction of seven red supergiants in Alicante 7 and three in Alicante 10 are consistent with them being members of the associations. One star toward Alicante 10 has kinematics and low extinction that are inconsistent with a membership. By means of spectral synthesis and line equivalent width measurements, we obtained chemical abundances for iron-peak, CNO, alpha, other light, and a few neutron-capture elements. We found average slightly subsolar iron abundances and solar-scaled [X/Fe] abundance patterns for most of the elements, consistent with a thin-disk chemistry. We found depletion of [C/Fe], enhancement of [N/Fe], and relatively low 12C/13C<15, which is consistent with CN cycled material and possibly some additional mixing in their atmospheres.