The Ages of A-Stars: Interferometric Observations of Our Brightest Neighbors
Abstract
The age of a star is one of its most fundamental parameters. Accurate ages of disk and/or planet hosting systems are essential for understanding their evolution, and accurate ages of stars which host directly-imaged planets are necessary for estimating the masses of such companions. Furthermore, accurate ages can be used to distinguish between proposed explanations for certain chemical peculiarities such as whether λ Boötis stars are young stars accreting clean gas, or more evolved stars experiencing mass loss.The rapid rotation of the vast majority of A-stars introduces two major difficulties to determining their ages. First, the gravity darkening induced by rapid rotation affects the observed properties of a star (e.g., flux, temperature, etc.) making them dependent on the star’s inclination. Secondly, it is predicted that this rotation changes how a star evolves both chemically and structurally relative to slowly rotating stellar models. Observations from optical interferometry can address the first concern and modern evolutionary models which account for rapid rotation can address and test the second. When used in conjunction, these can yield accurate age estimates for A-stars. Using observations from the CHARA Array interferometer and the MESA evolutionary models, we estimate the ages and masses of seven members of the coeval Ursa Major moving group leading to an age estimate for the group of 414 ± 23 Myr. We also estimate the age of the directly-imaged planet host star κ Andromedae finding it to be 47+27-40 Myr implying that the companion is in fact a low-mass brown dwarf with a mass of 22+8-9 MJup. Finally, we present new observations and preliminary age and mass estimates for five stars with the λ Boötis chemical peculiarity and for six members of the Hyades open cluster.
- Publication:
-
American Astronomical Society Meeting Abstracts #229
- Pub Date:
- January 2017
- Bibcode:
- 2017AAS...22913105J