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Asteroseismology provides fundamental stellar parameters independent ofdistance, but subject to systematics under calibration. Gaia DR2 has providedparallaxes for a billion stars, which are offset by a parallax zero-point. RedClump (RC) stars have a narrow spread in luminosity, thus functioning asstandard candles to calibrate these systematics. This work measures how themagnitude and spread of the RC in the Kepler field are affected by changes totemperature and scaling relations for seismology, and changes to the parallaxzero-point for Gaia. We use a sample of 5576 RC stars classified throughasteroseismology. We apply hierarchical Bayesian latent variable models,finding the population level properties of the RC with seismology, and usethose as priors on Gaia parallaxes to find the parallax zero-point offset. Wethen find the position of the RC using published values for the zero-point. Wefind a seismic temperature insensitive spread of the RC of ~0.03 mag in the2MASS K band and a larger and slightly temperature-dependent spread of ~0.13mag in the Gaia G band. This intrinsic dispersion in the K band provides adistance precision of ~1% for RC stars. Using Gaia data alone, we find a meanzero-point of -41 $\pm$ 10 $\mu$as. This offset yields RC absolute magnitudesof -1.634 $\pm$ 0.018 in K and 0.546 $\pm$ 0.016 in G. Obtaining these samevalues through seismology would require a global temperature shift of ~-70 K,which is compatible with known systematics in spectroscopy.

Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump