An absolutely calibratedT_effscale from the infrared flux method

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.

A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36−670839.3

“…The relation between equivalent width and interstellar reddening from [30] provides E(B-V) = 0.04 ± 0.01 which we adopt. Using the infrared flux method for the BVJHK system 31 (BV photometry from APASS 32 ; JHK from 2MASS 33 ) we derive a photometric temperature of T eff = 5,210 ± 64 K. From utilisation of griJHK 31 (gri from APASS) we determine T eff = 5,265 ± 76 K. These values and those determined through spectrophotometric analysis are in concordance.…”

The Galactic chemical evolution of oxygen inferred from 3D non-LTE spectral-line-formation calculations

“…For consistency, equivalent widths across the theoretical 3D non-LTE grid were computed by fitting Gaussian functions to the line fluxes and integrating analytically. Stellar parameters were taken from several recent studies (Casagrande et al 2010(Casagrande et al , 2011Nissen et al 2014). These T eff estimates were either derived using or critically compared to the accurate IRFM calibrations of Casagrande et al (2010); where more than one set of stellar parameters was available for a given star, the newest set was adopted.…”

Carbon abundances of reference late-type stars from 1D analysis of atomic C i and molecular CH lines

“…For HD 122563 we adopted T eff = 4600 K from Mashonkina et al (2011), and it is consistent with the recent value based on the interferometric observations of Creevey et al (2012 Notes. References: (1) Mashonkina et al (2003); (2) Mashonkina et al (2011); (3) Sitnova et al (2015) recommended by Sitnova et al (2015) based on the data of Alonso et al (1996), González Hernández & Bonifacio (2009), Casagrande et al (2010, and Casagrande et al (2011). For HD 29907 its effective temperature was determined from the Balmer line wing fits (Mashonkina et al 2003).…”