Unbiased TGAS$\times$LAMOST distances and the role of binarity

Understand

Spectrophotometric distances to stars observed by large spectroscopic surveys offer a crucial complement to parallax distances that remain very important also after the future Gaia data releases.

• Here we present a probabilistic approach to modeling spectroscopic information for a subset of 4,000 main sequence stars with good parallaxes ($\sigma_\varpi/\varpi<0.1$) from the LAMOST $\times$ TGAS $\times$ 2MASS cross-match, yielding a precise spectroscopic distance estimator with uncertainties of $\sim$6% for single stars.
• Unlike previous approaches to this problem, we explicitly account for the individual parallax uncertainties in the model building and fully incorporate the fraction of near-equal binaries of main sequence stars, which would lead to biased distance estimates if neglected.
• Using this model, we estimate the distance for all (150,000) main sequence stars from LAMOST Data Release 5, without parallax information.