Candidate RR Lyrae Associated with the Ultrafaint Dwarf Galaxy Aquarius III

TL;DR

This study identified a RR Lyrae star associated with the ultrafaint dwarf galaxy Aquarius III, marking the first such variable star linked to this galaxy, and analyzed its implications for the galaxy's stellar population.

Contribution

The paper reports the first identification of a RR Lyrae star associated with Aquarius III, combining catalog data and new observations to explore its stellar content.

Findings

A RR Lyrae star is associated with Aquarius III.

No RR Lyrae stars were found in the galaxy's central region.

Synthetic models suggest Aquarius III could host at least one RR Lyrae.

Abstract

We report the search of RR Lyrae in the vicinity of a newly discovered ultrafaint dwarf galaxy, Aquarius III. Based on the known RR Lyrae catalogs and $gri$-band light curves retrieved from public archives, we identified a RR Lyrae with distance, metallicity, and proper motion consistent with Aquarius III. Therefore, this RR Lyrae is the first variable star identified to be associated with Aquarius III, despite its projected distance is more than 15 times the half-light radius of Aquarius III. On the other hand, a dedicated time-series monitoring of the central part of Aquarius III, out to a projected radius of approximately four half-light radius, revealed there is no RR Lyrae in this region. We ran a set of synthetic color-magnitude diagrams with properties similar to Aquarius III, and found a non-negligible probability that Aquarius III could have (at least one) RR Lyrae. We have also identified a RR Lyrae candidate but most likely it is a background halo star.