Gaia EDR3 Parallax Zero-point Offset Based on W Ursae Majoris-type Eclipsing Binaries
Fangzhou Ren, Xiaodian Chen, Huawei Zhang, Richard de Grijs, Licai Deng, Yang Huang
Abstract
Abstract We independently determine the zero-point offset of the Gaia early Data Release-3 (EDR3) parallaxes based on ∼110,000 W Ursae Majoris (EW)-type eclipsing binary systems. EWs cover almost the entire sky and are characterized by a relatively complete coverage in magnitude and color. They are an excellent proxy for Galactic main-sequence stars. We derive a W1-band period–luminosity relation with a distance accuracy of 7.4%, which we use to anchor the Gaia parallax zero-point. The final, global parallax offsets are −28.6 ± 0.6 μ as and −25.4 ± 4.0 μ as (before correction) and 4.2 ± 0.5 μ as and 4.6 ± 3.7 μ as (after correction) for the five- and six-parameter solutions, respectively. The total systematic uncertainty is 1.8 μ as. The spatial distribution of the parallax offsets shows that the bias in the corrected Gaia EDR3 parallaxes is less than 10 μ as across 40% of the sky. Only 15% of the sky is characterized by a parallax offset greater than 30 μ as. Thus, we have provided independent evidence that the parallax zero-point correction provided by the Gaia team significantly reduces the prevailing bias. Combined with literature data, we find that the overall Gaia EDR3 parallax offsets for Galactic stars are [−20, −30] μ as and 4–10 μ as, respectively, before and after correction. For specific regions, an additional deviation of about 10 μ as is found.