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|Title:||Chemical abundances of giant stars in the Crater stellar system||Authors:||Bonifacio, P.
Andrievsky, S. M.
Korotin, S. A.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||579||First Page:||L6||Abstract:||Aims: We obtained spectra for two giants of Crater (Crater J113613-105227 and Crater J113615-105244) using X-Shooter at the VLT, with the purpose of determining their radial velocities and metallicities. Methods: Radial velocities were determined by cross-correlating the spectra with that of a standard star. The spectra were analysed with the MyGIsFOS code using a grid of synthetic spectra computed from one-dimensional, local thermodynamic equilibrium (LTE) model atmospheres. Effective temperature and surface gravity were derived from photometry measured from images obtained by the Dark Energy Survey. Results: The radial velocities are 144.3 ± 4.0 km s<SUP>-1</SUP> for Crater J113613-105227 and and 134.1 ± 4.0km s<SUP>-1</SUP> for Crater J113615-105244. The metallicities are [Fe/H] = -1.73 and [Fe/H] = -1.67, respectively. In addition to the iron abundance, we were able to determine abundances for nine elements: Na, Mg, Ca, Ti, V, Cr, Mn, Ni, and Ba. For Na and Ba we took into account deviations from LTE because the corrections are significant. The abundance ratios are similar in the two stars and resemble those of Galactic stars of the same metallicity. In the deep photometric images we detected several stars that lie to the blue of the turn-off. Conclusions: The radial velocities imply that both stars are members of the Crater stellar system. The difference in velocity between the two taken at face value implies a velocity dispersion >3.7 km s<SUP>-1</SUP> at a 95% confidence level. Our spectroscopic metallicities agree excellently well with those determined by previous investigations using photometry. Our deep photometry and the spectroscopic metallicity imply an age of 7 Gyr for the main population of the system. The stars to the blue of the turn-off can be interpreted as a younger population that is of the same metallicity and an age of 2.2 Gyr. Finally, spatial and kinematical parameters support the idea that this system is associated with the galaxies Leo IV and Leo V. All the observations favour the interpretation of Crater as a dwarf galaxy. Based on observations taken at ESO Paranal with the Kueyen telescope, programme 094.D-0547.Tables 3-4, Figs. 4-5, and Appendices are available in electronic form at "http://www.aanda.org/10.1051/0004-6361/201526366/olm"||Acknowledgments:||We are grateful to the anonymous referee, who helped us to improve the paper and pointed out to us that the almost horizontal track of the young population SGB does not follow the expected blue-straggler locus and that Crater must be near peri- or apo-galacticon or on a nearly circular orbit, providing an argument in favour of its ability to retain gas. The project was funded by FONDATION MERAC. P.B., E.C., P.F., M.S., F.S., and R.C. acknowledge support from the Programme National de Cosmologie et Galaxies (PNCG) and Programme National de Physique Stellaire (PNPS) of the Institut National de Sciences de l’Univers of CNRS. Support for L.S. was provided by Chile’s Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. S.Z. acknowledges that this research was supported in part by the National Science Foundation under Grant No. NSF PHY11-25915 and by PRIN INAF 2014 CRA 1.05.01.94.05 “Star won’t tell their ages to GAIA”. S.Z. warmly thank P. Ochner for useful observations at the Asiago telescopes.||URI:||http://hdl.handle.net/20.500.12386/24012||URL:||https://www.aanda.org/articles/aa/abs/2015/07/aa26366-15/aa26366-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201526366||Bibcode ADS:||2015A&A...579L...6B||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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