Red Clump Stars from the LAMOST data I: identification and distance

TL;DR

This paper presents a large sample of red clump stars from LAMOST data, employing an isochrone-based method to accurately estimate their distances and mitigate systematic biases related to initial mass and age.

Contribution

It introduces an isochrone-based approach for precise distance estimation of red clump stars, improving over traditional fixed luminosity assumptions.

Findings

Sample of 120,000 red clump candidates identified.

Distance estimates with less than 10% accuracy achieved.

Method effectively removes systematic biases related to initial mass and age.

Abstract

We present a sample of about 120,000 red clump candidates selected from the LAMOST DR2 catalog based on the empirical distribution model in the effective temperature vs. surface gravity plane. Although, in general, red clump stars are considered as the standard candle, they do not exactly stay in a narrow range of absolute magnitude, but may extend to more than 1 magnitude depending on their initial mass. Consequently, conventional oversimplified distance estimations with assumption of fixed luminosity may lead to systematic bias related to the initial mass or the age, which may potentially affect the study of the evolution of the Galaxy with red clump stars. We therefore employ an isochrone-based method to estimate the absolute magnitude of red clump stars from their observed surface gravities, effective temperatures, and metallicities. We verify that the estimation well removes the systematics and provide an initial mass/age independent distance estimates with accuracy less than 10%.