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arXiv · 2103.07432

Characterizing and correcting the proper motion bias of the bright Gaia EDR3 sources

Tristan Cantat-Gaudin·Timothy D. Brandt
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Abstract

In this paper we characterize magnitude-dependent systematics in the proper motions of the Gaia EDR3 catalog and provide a prescription for their removal. The reference frame of bright stars (G<13) in EDR3 is known to rotate with respect to extragalactic objects, but this rotation has proven difficult to characterize and correct. We employ a sample of binary stars and a sample of open cluster members to characterize this proper motion bias as a magnitude-dependent spin of the reference frame. We show that the bias varies with G magnitude, reaching up to 80 {\mu}as/yr for sources in the range G = 11 - 13, several times the formal EDR3 proper motion uncertainties. We also show evidence for an additional dependence on the color of the source, with a magnitude up to 10 {\mu}as/yr. However, a color correction proportional to the effective wavenumber is unsatisfactory for very red or very blue stars and we do not recommend its use. We provide a recipe for a magnitude-dependent correction to align the proper motion of the Gaia EDR3 sources brighter than G=13 with the International Celestial Reference Frame.

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Tristan Cantat-Gaudin, Timothy D. Brandt. 2021-03-12. Characterizing and correcting the proper motion bias of the bright Gaia EDR3 sources. https://doi.org/10.1051/0004-6361%2F202140807

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