A new Extended Main Sequence Turnoff star cluster in the Large Magellanic Cloud

TL;DR

This study characterizes the age, metallicity, and structural features of the LMC cluster SL 529, revealing it as the most metal-poor and oldest EMSTO cluster with an extended MSTO region and complex red clump structure.

Contribution

First detailed analysis of SL 529, establishing it as the oldest and most metal-poor EMSTO LMC cluster with an extended MSTO and unique red clump features.

Findings

SL 529 has an age of 2.25 Gyr and metallicity Z=0.004.

The cluster exhibits an extended MSTO region with an age spread of ~0.5 Gyr.

The red clump shows two star concentrations, possibly due to binary interactions.

Abstract

We present results on the age and metallicity estimates of the poorly studied LMC cluster SL 529, from CCD SDSS gr photometry obtained at the Gemini South telescope with the GMOS attached. The cluster MSTO region possesses an extended structure, with an age spread (~ 0.5 Gyr) bigger than the mean age width of known EMSTO LMC clusters. We report for the first time a mean cluster age of 2.25 Gyr and a mean cluster metallicity of Z=0.004, which place it as the most metal-poor and oldest cluster in the EMSTO LMC cluster group. In addition, the cluster RC appears to be formed by two concentrations of stars - although it is not clear whether this feature can be caused, in part, by binary interactions and mergers -, whereas the cluster core radius of 4.2 pc is in excellent agreement with those determined for the previously 12 known EMSTO LMC clusters.