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

Monelli, M.; Walker, A. R.; Martínez-Vázquez, C. E.; Stetson, P. B.; Gallart, C.; Bernard, E. J.; Bono, G.; Vivas, A. K.; Andreuzzi, G.; Dall'Ora, M.; Fiorentino, G.; Dorta, A.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 479, Issue 4, p.4279-4291

Advertised on:
10
2018
Number of authors
12
IAC number of authors
3
Citations
13
Refereed citations
11
Description
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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Matteo
Monelli