Bayesian analysis of ages, masses, and distances to cool stars with
  non-LTE spectroscopic parameters
  For studies of Galactic evolution, the accurate characterization of stars in
terms of their evolutionary stage and population membership is of fundamental
importance. A standard approach relies on extracting this information from
stellar evolution models but requires the effective temperature, surface
gravity, and metallicity of a star obtained by independent means. In previous
work, we determined accurate effective temperatures and non-LTE logg and [Fe/H]
(NLTE-Opt) for a large sample of metal-poor stars, -3<[Fe/H]<-0.5, selected
from the RAVE survey. As a continuation of that work, we derive here their
masses, ages, and distances using a Bayesian scheme and GARSTEC stellar tracks.
For comparison, we also use stellar parameters determined from the widely-used
1D LTE excitation-ionization balance of Fe (LTE-Fe). We find that the latter
leads to systematically underestimated stellar ages, by 10-30%, but
overestimated masses and distances. Metal-poor giants suffer from the largest
fractional distance biases of 70%. Furthermore, we compare our results with
those released by the RAVE collaboration for the stars in common (DR3, Zwitter
et al. 2010, Seibert et al. 2011). This reveals -400 to +400 K offsets in
effective temperature, -0.5 to 1.0 dex offsets in surface gravity, and 10 to
70% in distances. The systematic trends strongly resemble the correlation we
find between the NLTE-Opt and LTE-Fe parameters, indicating that the RAVE DR3
data may be affected by the physical limitations of the 1D LTE synthetic
spectra. Our results bear on any study, where spectrophotometric distances
underlie stellar kinematics. In particular, they shed new light on the debated
controversy about the Galactic halo origin raised by the SDSS/SEGUE
observations.
