The properties of RR Lyrae variable stars in the Local Group dwarf galaxy LGS-3

Abstract

We present a sample of 56 RR Lyrae variable stars (48 ab-type and 8 c-type) measured from a set of F475W (≈B filter) and F814W (≈I filter) archival images taken with the Hubble Space Telescope/Advanced Camera for Surveys of one field in the Local Group dwarf galaxy LGS-3 (also known as the Pisces Dwarf or Pisces I). The ab-type variables exhibit a mean period of =0.623 ± 0.007 d. Applying a relationship between [Fe/H] and period, we calculate a mean metallicity of ⟨[Fe/H]⟩ = -1.81 ± 0.04 on the Zinn & West scale. Finally, we conclude that the mean metal abundance of the RR Lyraes in LGS-3 is consistent with that of the LGS-3 field stellar population at an age of >10 Gyr.