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Variable stars in local group galaxies - IV. RR Lyrae stars in the central regions of the low-density galaxy Crater II

Abstract : We present a search and analysis of variable stars in the recently discovered Crater II dwarf galaxy. Based on B, V, I data collected with the Isaac Newton Telescope (FoV∼0.44 deg2), we detected 37 variable stars, of which 34 are bone-fide RR Lyrae stars of Crater II (28 RRab, 4 RRc, 2 RRd). We applied the metal-independent (V, B - V) Period-Wesenheit relation and derived a true distance modulus (μ = 20.30 ± 0.08 mag (σ = 0.16 mag). Individual metallicities for RR Lyrae stars were derived by inversion of the predicted I-band Period-Luminosity relation. We find a mean metallicity of [Fe/H] = -1.64 and a standard deviation of σ _{[Fe/H]}=0.21 dex, compatible with either negligible or vanishing intrinsic metallicity dispersion. The analysis of the colour-magnitude diagram reveals a stark paucity of blue horizontal branch stars, at odds with other Galactic dwarfs, and globular clusters with similar metal abundances.
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https://hal-insu.archives-ouvertes.fr/insu-03689234
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Submitted on : Tuesday, June 7, 2022 - 10:48:22 AM
Last modification on : Wednesday, June 8, 2022 - 3:34:27 AM

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M. Monelli, A. R. Walker, C. E. Martínez-Vázquez, P. B. Stetson, C. Gallart, et al.. Variable stars in local group galaxies - IV. RR Lyrae stars in the central regions of the low-density galaxy Crater II. Monthly Notices of the Royal Astronomical Society, 2018, 479, pp.4279-4291. ⟨10.1093/mnras/sty1645⟩. ⟨insu-03689234⟩

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