TGAS Error Renormalization from the RR Lyrae Period-Luminosity Relation

Abstract

The Gaia team has applied a renormalization to their internally-derived parallax errors ${\sigma }_{\mathrm{int}}(\pi )$ $${\sigma }_{tgas}(\pi )=\sqrt{[A{\sigma }_{int}(\pi ){]}^2+{\sigma }_0^2};(A,{\sigma }_0)=(1.4,0.20\mathrm{mas})$$ 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 $$(A,{\sigma }_0)=(1.1,0.12\mathrm{mas})(\mathrm{this}\mathrm{paper}).$$ 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: $${\sigma }_{true}(\pi )=\sqrt{(0.79{\sigma }_{tgas}(\pi ){)}^2-(0.10\mathrm{mas}{)}^2}.$$

5 pages, 2 figures

References in corpus (1)

• Gaia Parallax Zero Point From RR Lyrae Stars

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