A Simple Unified Spectroscopic Indicator of Stellar Luminosity: the Extended Flux Weighted Gravity-Luminosity Relationship

TL;DR

This paper introduces a new spectroscopic indicator, flux weighted gravity, that correlates tightly with stellar luminosity across a wide range of stellar types and evolutionary stages, enabling accurate distance estimates.

Contribution

It demonstrates both theoretically and observationally that flux weighted gravity is a reliable luminosity indicator for diverse stars, extending its applicability to large stellar surveys.

Findings

The flux weighted gravity correlates with absolute bolometric magnitude over 17 magnitudes.

The relation holds with a scatter of 0.17 to 0.29 mag across different luminosities.

It enables spectroscopic distance estimates with approximately 10% accuracy.

Abstract

We show that for a wide range of stellar masses, from 0.3 to 20 Msun, and for evolutionary phases from the main sequence to the beginning of the red giant stage, the stellar flux weighted gravity, g_F ~ g/Teff^4, is tightly correlated with absolute bolometric magnitude Mbol. Such a correlation is predicted by stellar evolution theory. We confirm this relation observationally, using a sample of 445 stars with precise stellar parameters. It holds over 17 stellar magnitudes from Mbol = 9.0 mag to -8.0 mag with a scatter of 0.17 mag above Mbol = -3.0 and 0.29 mag below this value. We then test the relation with 2.2 million stars with 6.5 mag > Mbol > 0.5 mag, where 'mass-produced' but robust log g, Teff and Mbol from LAMOST DR5 and Gaia DR2 are available. We find that the same relation holds with a scatter of ~0.2 mag for single stars offering a simple spectroscopic distance estimate good to ~10 percent.