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

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 $I_{\mathrm{c}}$ 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 ($75.3_{-10.9}^{+12.8}$ and $79.8_{-9.9}^{+11.5}$ 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 $[Fe/H]\sim -1.9$, than any other known system with Miras.

Accepted by ApJL, 21 pages, 1 figure, 4 tables

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Cited by in corpus (4)

• Tracing the tidal streams of the Sagittarius dSph, and halo Milky Way features, with carbon-rich long-period variables
• Age Gradients Throughout the Galaxy with O-Miras
• The period-age relation of long-period variables
• Zwicky Transient Facility and Globular Clusters: the gr-Band Period-Luminosity Relations for Mira Variables at Maximum Light and Their Applications to Local Galaxies