Testing asteroseismology with Gaia DR2: hierarchical models of the Red Clump
Abstract
Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zeropoint (ϖ_{zp}). Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate these systematics. This work measures how the magnitude and spread of the RC in the Kepler field are affected by changes to temperature and scaling relations for seismology, and changes to the parallax zeropoint for Gaia. We use a sample of 5576 RC stars classified through asteroseismology. We apply hierarchical Bayesian latent variable models, finding the populationlevel properties of the RC with seismology, and use those as priors on Gaia parallaxes to find ϖ_{zp}. We then find the position of the RC, using published values for ϖ_{zp}. We find a seismic temperatureinsensitive spread of the RC of {∼ }0.03 mag in the 2MASS K band and a larger and slightly temperaturedependent spread of {∼ }0.13 mag in the Gaia G band. This intrinsic dispersion in the K band provides a distance precision of {∼ } 1{{ per cent}} for RC stars. Using Gaia data alone, we find a mean zeropoint of 41± 10 μ as. This offset yields RC absolute magnitudes of 1.634 ± 0.018 in K and 0.546 ± 0.016 in G. Obtaining these same values through seismology would require a global temperature shift of {∼ }70 K, which is compatible with known systematics in spectroscopy.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 July 2019
 DOI:
 10.1093/mnras/stz1092
 arXiv:
 arXiv:1904.07919
 Bibcode:
 2019MNRAS.486.3569H
 Keywords:

 asteroseismology;
 parallaxes;
 stars: fundamental parameters;
 stars: statistics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 Accepted for publication in MNRAS