Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes

Keivan G. Stassun, Guillermo Torres

Published 2018-05-08Version 1

We previously used the sample of eclipsing binaries with accurate, empirical distances from Stassun & Torres (2016) to test the parallaxes reported in the Gaia first data release, finding an average offset of $-0.25 \pm 0.05$ mas in the sense of the Gaia parallaxes being too small (i.e., the distances too long). Here we reprise that analysis, now comparing to the parallaxes from the Gaia second data release (DR2). We find evidence for a systematic offset, at 98% confidence, of $-82 \pm 33$ muas, again in the sense of the Gaia parallaxes being too small, for distances in the range spanned by the eclipsing binary sample (0.03--3 kpc). The offset does not appear to depend strongly on distance within this range, though there is marginal evidence that the offset increases (becomes slightly more negative) for distances $\gtrsim 1$ kpc, up to the 3 kpc distances probed by the test sample. The offset reported here is consistent with the expectation that global systematics in the Gaia DR2 parallaxes are below 100 muas.