Discovery of Mira variable stars in the metal-poor Sextans dwarf spheroidal galaxy

TL;DR

This paper reports the discovery of two Mira variable stars in the metal-poor Sextans dwarf spheroidal galaxy, providing new insights into stellar populations in low-metallicity environments.

Contribution

First identification of Miras in a galaxy with [Fe/H] around -1.9, expanding understanding of variable stars in metal-poor systems.

Findings

Distances consistent with Sextans dSph membership

First Miras found in such a low-metallicity environment

Light curves show large amplitude and long periods

Abstract

We report the discovery of two Mira variable stars (Miras) toward the Sextans dwarf spheroidal (dSph) galaxy. We performed optical long-term monitoring observations for two red stars in the Sextans dSph. The light curves of both stars in the $I_{\rm c}$ band show large-amplitude (3.7 and 0.9 mag) and long-period ($326\pm 15$ and $122\pm 5$ days) variations, suggesting that they are Miras. We combine our own infrared data with previously published data to estimate the mean infrared magnitudes. The distances obtained from the period-luminosity relation of the Miras ($75.3^{+12.8}_{-10.9}$ and $79.8^{+11.5}_{-9.9}$ kpc, respectively), together with the radial velocities available, support memberships of the Sextans dSph ($90.0\pm 10.0$ kpc). These are the first Miras found in a stellar system with a metallicity as low as ${\rm [Fe/H]\sim -1.9}$, than any other known system with Miras.