Serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy

TL;DR

This paper reports the serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy, demonstrating their utility in identifying distant faint stellar systems in the Milky Way's outskirts.

Contribution

It presents the first identification of RR Lyrae stars in Leo V, establishing a new method for detecting faint satellite galaxies using variable stars.

Findings

Distance to Leo V is 173 +/- 5 kpc.

RR Lyrae stars belong to Oosterhoff II group.

Distant RR Lyrae can reveal unknown faint systems.

Abstract

During the analysis of RR Lyrae stars discovered in the High cadence Transient Survey (HiTS) taken with the Dark Energy Camera at the 4-m telescope at Cerro Tololo Inter-American Observatory, we found a group of three very distant, fundamental mode pulsator RR Lyrae (type ab). The location of these stars agrees with them belonging to the Leo V ultra-faint satellite galaxy, for which no variable stars have been reported to date. The heliocentric distance derived for Leo V based on these stars is 173 +/- 5 kpc. The pulsational properties (amplitudes and periods) of these stars locate them within the locus of the Oosterhoff II group, similar to most other ultra-faint galaxies with known RR Lyrae stars. This serendipitous discovery shows that distant RR Lyrae stars may be used to search for unknown faint stellar systems in the outskirts of the Milky Way.