Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry

Abstract

Astrometric surveys provide the opportunity to measure the absolute\nmagnitudes of large numbers of stars, but only if the individual line-of-sight\nextinctions are known. Unfortunately, extinction is highly degenerate with\nstellar effective temperature when estimated from broad band optical/infrared\nphotometry. To address this problem, I introduce a Bayesian method for\nestimating the intrinsic parameters of a star and its line-of-sight extinction.\nIt uses both photometry and parallaxes in a self-consistent manner in order to\nprovide a non-parametric posterior probability distribution over the\nparameters. The method makes explicit use of domain knowledge by employing the\nHertzsprung--Russell Diagram (HRD) to constrain solutions and to ensure that\nthey respect stellar physics. I first demonstrate this method by using it to\nestimate effective temperature and extinction from BVJHK data for a set of\nartificially reddened Hipparcos stars, for which accurate effective\ntemperatures have been estimated from high resolution spectroscopy. Using just\nthe four colours, we see the expected strong degeneracy (positive correlation)\nbetween the temperature and extinction. Introducing the parallax, apparent\nmagnitude and the HRD reduces this degeneracy and improves both the precision\n(reduces the error bars) and the accuracy of the parameter estimates, the\nlatter by about 35%. The resulting accuracy is about 200K in temperature and\n0.2mag in extinction. I then apply the method to estimate these parameters and\nabsolute magnitudes for some 47000 F,G,K Hipparcos stars which have been\ncross-matched with 2MASS. The method can easily be extended to incorporate the\nestimation of other parameters, in particular metallicity and surface gravity,\nmaking it particularly suitable for the analysis of the 10^9 stars from Gaia.\n

Keywords

Affiliated Institutions

• Harvard University US
• Max Planck Institute for Astronomy DE

Related Publications