Astrometric excess noise in Gaia DR2 and the search for X-ray emitting binaries

Understand

Astrometric noise in excess of parallax and proper motion could be a signature of orbital wobble of individual components in binary star systems.

• The combination of X-ray selection with astrometric noise can then be a powerful tool for identifying accreting binaries.
• Here, we mine the Gaia DR2 catalogue for Galactic sources with significant values of astrometric noise over the parameter space expected for known and candidate X-ray binaries (XRBs).
• Cross-matching our sample with the Chandra Source Catalogue CSC2.0 returns a primary sample of ~1,500 X-ray sources with significant excess noise, constituting ~0.04% of the initial Gaia sample.