# The Age and Metallicity Dependence of the Near-Infrared Magnitudes of Red Clump Stars

## TL;DR

This study empirically investigates how the near-infrared magnitudes and colours of red clump stars depend on age and metallicity by analyzing star clusters in the Large Magellanic Cloud, improving their use as standard candles.

## Contribution

It provides new empirical relations for the age and metallicity dependence of red clump stars' near-infrared magnitudes and colours, filling observational gaps in this parameter space.

## Key findings

- Near-infrared magnitudes depend strongly on age for young RC stars.
- Colours $J - K_{S}$ and $H - K_{S}$ are nearly constant within certain age and metallicity ranges.
- Observed population effects agree with model predictions.

## Abstract

Red clump (RC) stars are widely used as an excellent standard candle. To make them even better, it is important to know the dependence of their absolute magnitudes on age and metallicity. We observed star clusters in the Large Magellanic Cloud to fill age and metallicity parameter space, which previous work has not observationally studied. We obtained the empirical relations of the age and metallicity dependence of absolute magnitudes $M_{J}$, $M_{H}$, and $M_{K_{S}}$, and colours $J - H$, $J - K_{S}$, and $H - K_{S}$ of RC stars, although the coefficients have large errors. Mean near-infrared magnitudes of the RC stars in the clusters show relatively strong dependence on age for young RC stars. The $J - K_{S}$ and $H - K_{S}$ colours show the nearly constant values of $0.528 \pm 0.015$ and $0.047 \pm 0.011$, respectively, at least within the ages of 1.1--3.2 Gyr and [Fe/H] of $-0.90$ to $-0.40$ dex. We also confirmed that the population effects of observational data are in good agreement with the model prediction.