Kavli Affiliate: Huawei Zhang
| First 5 Authors: Fangzhou Ren, Xiaodian Chen, Huawei Zhang, Richard de Grijs, Licai Deng
| Summary:
We independently determine the zero-point offset of the Gaia early Data
Release-3 (EDR3) parallaxes based on $sim 110,000$ 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 $-28.6pm0.6$
$mu$as and $-25.4pm4.0$ $mu$as (before correction) and $4.2pm0.5$ $mu$as
and $4.6pm3.7$ $mu$as (after correction) for the five- and six-parameter
solutions, respectively. The total systematic uncertainty is $1.8$ $mu$as. The
spatial distribution of the parallax offsets shows that the bias in the
corrected Gaia EDR3 parallaxes is less than 10 $mu$as across $40%$ of the
sky. Only $15%$ of the sky is characterized by a parallax offset greater than
30 $mu$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 $[-20, -30]$ $mu$as and 4-10
$mu$as, respectively, before and after correction. For specific regions, an
additional deviation of about 10 $mu$as is found.
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