Empirical Bolometric Fluxes and Angular Diameters of 1.6 Million Tycho-2 Stars and Radii of 350,000 Stars with \emph{Gaia} DR1 Parallaxes

TL;DR

This paper provides empirical bolometric fluxes, angular diameters, and radii for over 1.6 million Tycho-2 stars using Gaia DR1 parallaxes, enabling improved stellar characterization and HR diagram analysis.

Contribution

It introduces a large-scale empirical catalog of stellar parameters for Tycho-2 stars, validated against spectroscopic data, and demonstrates its reliability for stars with temperatures below 7000 K.

Findings

Median uncertainties: 1.4% in bolometric flux, 2.4% in angular diameters, 7.5% in radii.

Over half a million stellar radii are now empirically determined for Tycho-2 stars.

Empirical HR diagrams clearly distinguish dwarf, subgiant, and giant populations.

Abstract

We present bolometric fluxes and angular diameters for over 1.6 million stars in the {\it Tycho-2} catalog, determined using previously-determined empirical color-temperature and color-flux relations. We vet these relations via full fits to the full broadband spectral energy distributions for a subset of benchmark stars, and perform quality checks against the large set of stars for which spectroscopically-determined parameters are available from LAMOST, RAVE, and/or APOGEE. We then estimate radii for the 355,502 {\it Tycho-2} stars in our sample whose \emph{Gaia} DR1 parallaxes are precise to $\lesssim$10\%. For the 64,960 of these stars with external spectroscopic information, we achieve median uncertainties on the effective temperatures, bolometric fluxes, angular diameters, and radii of $1.0\%$, $1.4\%$, $2.4\%$, and $7.5\%$, respectively. For the 290,542 remaining stars, we achieve median uncertainties of $0.9\%$, $1.3\%$, $2.2\%$, and $7.5\%$, respectively. These stellar parameters are shown to be reliable for stars with $T_{\rm eff}\lesssim$7000~K. The over half a million bolometric fluxes and angular diameters presented here will serve as an immediate trove of empirical stellar radii with the {\it Gaia\/} second data release, at which point effective temperature uncertainties will dominate the radius uncertainties. Already, dwarf, subgiant, and giant populations are readily identifiable in our purely empirical luminosity-effective temperature (theoretical) Hertzsprung-Russell diagrams.