The Parallax Zero-Point of Gaia Early Data Release 3 from LAMOST Primary Red Clump Stars

TL;DR

This study assesses Gaia EDR3's parallax zero-point using LAMOST red clump stars, finding a median offset of 26 microarcseconds with dependencies on magnitude, color, and position, and proposing corrections to improve accuracy.

Contribution

It provides an independent analysis of Gaia EDR3's parallax zero-point using LAMOST red clump stars, identifying dependencies and proposing corrections for improved accuracy.

Findings

Median parallax offset of 26 μas detected

Dependencies on magnitude, color, and position confirmed

Significant residual offsets remain after correction

Abstract

We present an independent examination of the parallax zero-point of the Third Gaia Early Data Release (hereafter EDR3), using the LAMOST primary red clump (PRC) stellar sample. A median parallax offset of around $26 \mu$as, slightly larger than that found by examination of distant quasars, is found for both the five- and six-parameter solutions in EDR3, based on samples of over 63,000 and 2000 PRC stars, respectively. Similar to the previous investigation of Lindegren et al., to which we compare our results, the parallax zero-point exhibits clear dependencies on the $G$ magnitudes, colors, and positions of the objects. Based on our analysis, the zero-point of the revised parallax can be reduced to a few $\mu$as, and some significant patterns, e.g., discontinuities with stellar magnitude, can be properly removed. However, relatively large offsets ($> 10 \mu$as) are still found for the revised parallaxes over different positions on the sky.