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 zero-point ( \varpi _ { 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 zero-point for Gaia .
We use a sample of 5576 RC stars classified through asteroseismology .
We apply hierarchical Bayesian latent variable models , finding the population level properties of the RC with seismology , and use those as priors on Gaia parallaxes to find \varpi _ { zp } .
We then find the position of the RC using published values for \varpi _ { zp } .
We find a seismic temperature insensitive spread of the RC of \sim 0.03 mag in the 2MASS K band and a larger and slightly temperature-dependent spread of \sim 0.13 mag in the Gaia G band .
This intrinsic dispersion in the K band provides a distance precision of \sim 1 \% for RC stars .
Using Gaia data alone , we find a mean zero-point of -41 \pm 10 \mu as .
This offset yields RC absolute magnitudes of -1.634 \pm 0.018 in K and 0.546 \pm 0.016 in G .
Obtaining these same values through seismology would require a global temperature shift of \sim - 70 K , which is compatible with known systematics in spectroscopy .