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تسجيل مستخدم جديدEvidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
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We reprise the analysis of Stassun & Torres (2016), comparing the parallaxes of the eclipsing binaries reported in that paper to the parallaxes newly reported in the Gaia second data release (DR2). We find evidence for a systematic offset of $-82 pm 33$ micro-arcseconds, in the sense of the Gaia parallaxes being too small, for brightnesses $(G lesssim 12)$ and for distances (0.03--3 kpc) in the ranges spanned by the eclipsing binary sample. 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 micro-arcseconds.
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We test the parallaxes reported in the Gaia first data release using the sample of eclipsing binaries with accurate, empirical distances from Stassun & Torres (2016). We find an average offset of $-$0.25$pm$0.05 mas in the sense of the Gaia parallaxe
s being too small (i.e., the distances too long). The offset does not depend strongly on obvious parameters such as color or brightness. However, we find with high confidence that the offset may depend on ecliptic latitude: the mean offset is $-$0.38$pm$0.06 mas in the ecliptic north and $-$0.05$pm$0.09 mas in the ecliptic south. The ecliptic latitude dependence may also be represented by the linear relation, $Deltapi approx -0.22(pm0.05) -0.003(pm0.001)timesbeta$ mas ($beta$ in degrees). Finally, there is a possible dependence of the parallax offset on distance, with the offset becoming negligible for $pilesssim 1$ mas; we discuss whether this could be caused by a systematic error in the eclipsing binary distance scale, and reject this interpretation as unlikely.
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