Catalog of Integrated-Light Star Cluster Light Curves in TESS

TL;DR

This paper introduces a new method for extracting integrated light curves of star clusters from TESS data, enabling the study of stellar variability in clusters across multiple galaxies.

Contribution

It presents the ELK package for background correction and systematics removal, providing high-quality light curves for 348 clusters and enabling variability analysis in integrated stellar populations.

Findings

Detection of variability in known Cepheid and RR Lyrae stars within clusters

Confirmation that low-amplitude variability persists in integrated light

Availability of a public tool for cluster light curve extraction

Abstract

We present the first integrated light, TESS-based light curves for star clusters in the Milky Way, Small Magellanic Cloud, and Large Magellanic Cloud. We explore the information encoded in these light curves, with particular emphasis on variability. We describe our publicly available package ELK, which is designed to extract the light curves by applying principal component analysis to perform background light correction, and incorporating corrections for TESS systematics, allowing us to detect variability on time scales shorter than ~10 days. We perform a series of checks to ensure the quality of our light curves, removing observations where systematics are identified as dominant features, and deliver light curves for 348 previously-cataloged open and globular clusters. Where TESS has observed a cluster in more than one observing sectors, we provide separate light curves for each sector (for a total of 2204 light curves). We explore in detail the light curves of star clusters known to contain high-amplitude Cepheid and RR Lyrae variable stars, and confirm that the variability of these known variables is still detectable when summed together with the light from thousands of other stars. We also demonstrate that even some low-amplitude stellar variability is preserved when integrating over a stellar population.