The TGAS HR diagram of S-type stars
Abstract
S-type stars are late-type giants enhanced with s-process elements originating either from nucleosynthesis during the Asymptotic Giant Branch (AGB) or from a pollution by a binary companion. The former are called intrinsic S stars, and the latter extrinsic S stars. The atmospheric parameters of S stars are more numerous than those of M-type giants (C/O ratio and s-process abundances affect the thermal structure and spectral synthesis), and hence they are more difficult to derive. Nevertheless, high-resolution spectroscopic data of S stars combined with the TGAS (Tycho-Gaia Astrometric solution) parallaxes were used to derive effective temperatures, surface gravities, and luminosities. These parameters allow to locate the intrinsic and extrinsic S stars in the Hertzsprung-Russell diagram.
- Publication:
-
Astrometry and Astrophysics in the Gaia Sky
- Pub Date:
- April 2018
- DOI:
- 10.1017/S1743921317005610
- Bibcode:
- 2018IAUS..330..345S
- Keywords:
-
- S stars;
- AGB stars;
- TGAS;
- HR diagram