Absolute Magnitude Calibration for Red Clump Stars

TL;DR

This paper presents a new calibration of the absolute magnitude of red clump stars using combined photometric and parallax data, resulting in more precise estimates than previous methods.

Contribution

It introduces a linear polynomial relation for $M_{K_s}$ based on $V-K_s$ color, improving the accuracy of red clump star distance measurements.

Findings

Smaller residuals in absolute magnitude estimates compared to previous methods.

More accurate calibration reduces the standard deviation of magnitude residuals.

The new relation outperforms mean magnitude assumptions for red clump stars.

Abstract

We combined the ($K_s$, $J-K_s$) data in Laney et al. (2012) with the $V$ apparent magnitudes and trigonometric parallaxes taken from the Hipparcos catalogue and used them to fit the $M_{K_s}$ absolute magnitude to a linear polynomial in terms of $V-K_s$ colour. The mean and standard deviation of the absolute magnitude residuals, -0.001 and 0.195 mag, respectively, estimated for 224 red clump stars in Laney et al. 2012 are (absolutely) smaller than the corresponding ones estimated by the procedure which adopts a mean $M_{K_s}=-1.613$ mag absolute magnitude for all red clump stars, -0.053 and 0.218 mag, respectively. The statistics estimated by applying the linear equation to the data of 282 red clump stars in Alves (2000) are larger, $\Delta M_{K_s}=0.209$ and $\sigma=0.524$ mag, which can be explained by a different absolute magnitude trend, i.e. condensation along a horizontal distribution.