The odd bunch: chrono-chemo-dynamics of sixteen unusual stars from Kepler
Abstract
In this study we combine asteroseismic, spectroscopic, and kinematic information to perform a detailed analysis of a sample of 16 stars from the Kepler field. Our selection focuses on stars that appear to contradict Galactic chemical evolution models: young and α-rich, old and metal-rich, as well as other targets with unclear classification in past surveys. Kinematics are derived from Gaia DR3 parallaxes and proper motions, and high-resolution spectra from HIRES/Keck are used to calculate chemical abundances for over 20 elements. This information is used to perform careful checks on asteroseismic masses and ages derived via grid-based modelling. Among the seven stars previously classified as young and α-rich, only one seems to be an unambiguously older object masking its true age. We confirm the existence of two very old (≥11 Gyr), super metal-rich (≥0.1 dex) giants. These two stars have regular thin disc chemistry and in-plane solar circle orbits that fit well in the picture of radial migration via the churning mechanism. The alternative explanation that these stars have younger ages would require mass-loss rates that strongly increase with increasing metallicity. Finally, we suggest further investigations to explore the suitability of Zn as a chemical clock in red giants.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2023
- DOI:
- 10.1093/mnras/stad1365
- arXiv:
- arXiv:2305.05024
- Bibcode:
- 2023MNRAS.523.1089A
- Keywords:
-
- stars: fundamental parameters;
- Galaxy: abundances;
- Galaxy: kinematics and dynamics;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 10 pages, 7 figures, accepted for publication in MNRAS