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|Title:||Chemical abundances of solar neighbourhood RR Lyrae stars||Authors:||PANCINO, ELENA
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||447||Issue:||3||First Page:||2404||Abstract:||We have analysed a sample of 18 RR Lyrae stars (17 fundamental-mode - RRab - and one first overtone - RRc) and three Population II Cepheids (two BL Her stars and one W Vir star), for which high-resolution (R ≥ 30 000), high signal-to-noise (S/N ≥ 30) spectra were obtained with either SARG at the Telescopio Nazionale Galileo (La Palma, Spain) or UVES at the European Southern Observatory Very Large Telescope (Paranal, Chile). Archival data were also analysed for a few stars, sampling ≳3 phases for each star. We obtained atmospheric parameters (T<SUB>eff</SUB>, log g, v<SUB>t</SUB>, and [M/H]) and abundances of several iron-peak and α-elements (Fe, Cr, Ni, Mg, Ca, Si, and Ti) for different pulsational phases, obtaining <[α/Fe]> = +0.31±0.19 dex over the entire sample covering -2.2 < [Fe/H] < -1.1 dex. We find that silicon is indeed extremely sensitive to the phase, as reported by previous authors, and cannot be reliably determined. Apart from this, metallicities and abundance ratios are consistently determined, regardless of the phase, within 0.10-0.15 dex, although caution should be used in the range 0 ≲ φ ≲ 0.15. Our results agree with literature determinations for both variable and non-variable field stars, obtained with very different methods, including low- and high-resolution spectroscopy. W Vir and BL Her stars, at least in the sampled phases, appear indistinguishable from RRab from the spectroscopic analysis point of view. Our large sample, covering all pulsation phases, confirms that chemical abundances can be obtained for RR Lyrae with the classical equivalent-width -based technique and static model atmospheres, even rather close to the shock phases.||Acknowledgments:||We would like to thank E. Bernard for useful discussions on the [Fe/H] calibrations of RR Lyrae based on pulsation properties, and G. Fiorentino for help on the Population II Cepheids properties and classification. We warmly thank C. Sneden, who was the referee of this paper, for his insightful comments. NB acknowledges the support of the European Commission Erasmus Mundus LOT 7 programme and warmly thanks the INAF – Bologna Observatory, where most of this work was carried out, for the hospitality during the grant stay. DR acknowledges financial support from PRIN MIUR 2010–2011, project ‘The chemical and dynamical evolution of the Milky Way and Local Group galaxies’, prot. 2010LYSN2T. This publication makes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration (NASA) and the National Science Foundation. This publication makes use of the data from the Northern Sky Variability Survey (NSVS) created jointly by the Los Alamos National Laboratory and University of Michigan. The NSVS was funded by the Department of Energy, NASA, and the National Science Foundation. This research made use of the products of the Cosmic-Lab project funded by the European Research Council. In this work, we made extensive use of the NASA ADS abstract service, of the Strasbourg CDS data base, and of the atomic data compiled in the VALD data base.||URI:||http://hdl.handle.net/20.500.12386/23071||URL:||https://academic.oup.com/mnras/article/447/3/2404/2892803||ISSN:||0035-8711||DOI:||10.1093/mnras/stu2616||Bibcode ADS:||2015MNRAS.447.2404P||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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