The Gaia team has applied a renormalization to their internally-derived parallax errors σint(π)σtgas(π)=[Aσint(π)]2+σ02;(A,σ0)=(1.4,0.20mas) based on comparison to Hipparcos astrometry. We use a completely independent method based on the RR Lyrae K-band period-luminosity relation to derive a substantially different result, with smaller ultimate errors (A,σ0)=(1.1,0.12mas)(thispaper). We argue that our estimate is likely to be more accurate and therefore that the reported TGAS parallax errors should be reduced according to the prescription: σtrue(π)=(0.79σtgas(π))2−(0.10mas)2.
Cite
@article{arxiv.1609.06315,
title = {TGAS Error Renormalization from the RR Lyrae Period-Luminosity Relation},
author = {Andrew Gould and Juna A. Kollmeier and Branimir Sesar},
journal= {arXiv preprint arXiv:1609.06315},
year = {2016}
}