Validation of the Gaia Early Data Release 3 parallax zero-point model with asteroseismology

Understand

The Gaia Early Data Release 3 (EDR3) provides trigonometric parallaxes for 1.5 billion stars, with reduced systematics compared to Gaia Data Release 2 and reported precisions better by up to a factor of two.

• New to EDR3 is a tentative model for correcting the parallaxes of magnitude-, position-, and color-dependent systematics for five- and six-parameter astrometric solutions, $Z_5$ and $Z_6$.
• Using a sample of over 2,000 first-ascent red giant branch stars with asteroseismic parallaxes, I perform an independent check of the $Z_5$ model in a Gaia magnitude range of $9 \lesssim G \lesssim 13$ and color range of $1.4\mu \mathrm{m} ^{-1} \lesssim \nu_{\mathrm{eff}} \lesssim 1.5 \mu \mathrm{m} ^{-1}$.
• This analysis therefore bridges the Gaia team's consistency check of $Z_5$ for $G > 13$, and indications from independent analysis using Cepheids of a $\approx 15 \mu \mathrm{as}$ over-correction for $G < 11$.