@article{a4bd338cb8504481a579b3b6889077fe,
title = "VARIABLE STARS in the FIELD of the HYDRA II ULTRA-FAINT DWARF GALAXY",
abstract = "We report the discovery of one RR Lyrae star in the ultra-faint satellite galaxy Hydra II based on time series photometry in the g, r and i bands obtained with the Dark Energy Camera at Cerro Tololo Inter-American Observatory, Chile. The association of the RR Lyrae star discovered here with Hydra II is clear because is located at 42″ from the center of the dwarf, well within its half-light radius of 102″. The RR Lyrae star has a mean magnitude of i= 21.30 ± 0.04 which is too faint to be a field halo star. This magnitude translates to a heliocentric distance of 151 ± 8 kpc for Hydra II; this value is ∼13%larger than the estimate from the discovery paper based on the average magnitude of several blue horizontal branch star candidates. The new distance implies a slightly larger half-light radius of 76+12 -10pc and a brighter absolute magnitude of Mv = -5.1 ± 0.3, which keeps this object within the realm of the dwarf galaxies. A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.",
keywords = "Local Group, galaxies: dwarf, galaxies: individual (Hydra II), stars: variables: RR Lyrae, stars: variables: general",
author = "Vivas, {A. Katherina} and Knut Olsen and Robert Blum and Nidever, {David L.} and Walker, {Alistair R.} and Martin, {Nicolas F.} and Gurtina Besla and Carme Gallart and Marel, {Roeland P.Van Der} and Majewski, {Steven R.} and Kaleida, {Catherine C.} and Mu{\~n}oz, {Ricardo R.} and Abhijit Saha and Conn, {Blair C.} and Shoko Jin",
note = "Funding Information: The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenossische Technische Hochschule (ETH) Zurich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciencies de lEspai (IEEC/CSIC), the Institut de Fisica dAltes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universitat Munchen and the associated Excellence Cluster universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, the Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University. We thank the anonymous referee for interesting suggestions that improved the content of this paper. S.M. acknowledges support from grant NSF-AST1312863. Publisher Copyright: {\textcopyright} 2016. The American Astronomical Society. All rights reserved.",
year = "2016",
month = may,
doi = "10.3847/0004-6256/151/5/118",
language = "English (US)",
volume = "151",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "5",
}