An absolutely calibrated<i>T</i>_effscale from the infrared flux method

TLDR

Various effective temperature scales have been proposed over the years, yet systematic differences of order 100 K or more persist. We investigate the source of these discrepancies using the Infrared Flux Method to pinpoint their origin. By employing a large sample of solar twins, we set the absolute zero point of the effective temperature scale to within a few degrees. Our calibrated scale, accurate to a few degrees, applies to dwarfs and subgiants from super‑solar to the most metal‑poor stars, validating spectroscopic temperatures at solar metallicity and giving temperatures up to 200 K hotter for [Fe/H] < –2.5, with derived bolometric corrections and photometric relations validated by interferometry and space spectrophotometry.

Abstract

Various effective temperature scales have been proposed over the years. Despite much work and the high internal precision usually achieved, systematic differences of order 100 K (or more) among various scales are still present. We present an investigation based on the Infrared Flux Method aimed at assessing the source of such discrepancies and pin down their origin. We break the impasse among different scales by using a large set of solar twins, stars which are spectroscopically and photometrically identical to the Sun, to set the absolute zero point of the effective temperature scale to within few degrees. Our newly calibrated, accurate and precise temperature scale applies to dwarfs and subgiants, from super-solar metallicities to the most metal-poor stars currently known. At solar metallicities our results validate spectroscopic effective temperature scales, whereas for [Fe/H]<-2.5 our temperatures are roughly 100 K hotter than those determined from model fits to the Balmer lines and 200 K hotter than those obtained from the excitation equilibrium of Fe lines. Empirical bolometric corrections and useful relations linking photometric indices to effective temperatures and angular diameters have been derived. Our results take full advantage of the high accuracy reached in absolute calibration in recent years and are further validated by interferometric angular diameters and space based spectrophotometry over a wide range of effective temperatures and metallicities.