The GALAH survey: effective temperature calibration from the InfraRed Flux Method in the Gaia system

TL;DR

This paper develops and validates new Gaia-based colour-temperature relations for stars, improving temperature estimates across various stellar types and metallicities using the InfraRed Flux Method.

Contribution

It introduces Gaia and 2MASS photometry into the InfraRed Flux Method to derive accurate, metallicity- and gravity-dependent temperature calibrations for over 360,000 stars in the GALAH DR3 survey.

Findings

Calibrations achieve 40-80 K internal uncertainty.

Validated against solar-twins, Gaia benchmark stars, and interferometry.

Provides guidelines for applying the temperature relations.

Abstract

In order to accurately determine stellar properties, knowledge of the effective temperature of stars is vital. We implement Gaia and 2MASS photometry in the InfraRed Flux Method and apply it to over 360,000 stars across different evolutionary stages in the GALAH DR3 survey. We derive colour-effective temperature relations that take into account the effect of metallicity and surface gravity over the range 4000 to 8000 kelvin, from very metal-poor stars to super solar metallicities. The internal uncertainty of these calibrations is of order 40-80 kelvin depending on the colour combination used. Comparison against solar-twins, Gaia benchmark stars and the latest interferometric measurements validates the precision and accuracy of these calibrations from F to early M spectral types. We assess the impact of various sources of uncertainties, including the assumed extinction law, and provide guidelines to use our relations. Robust solar colours are also derived.