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New results on field and cluster RR Lyraes

Published online by Cambridge University Press:  15 February 2018

G. Clementini ,
R. Merighi ,
M. Tosi ,
R. Gratton  and
E. Carretta
G. Clementini
Affiliation:
Osservatorio Astronomico, Bologna, Italy
R. Merighi
Affiliation:
Osservatorio Astronomico, Bologna, Italy
M. Tosi
Affiliation:
Osservatorio Astronomico, Bologna, Italy
R. Gratton
Affiliation:
Osservatorio Astronomico, Padova, Italy
E. Carretta
Affiliation:
Dipartimento di Astronomia, Padova, Italy

Abstract

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RR Lyrae stars both in the field and in clusters can be used to derive the metal abundance of the regions and systems where they are found.

(1) New data have been collected on a sample of field ab-type RR Lyraes with the aim of studying the composition of the halo and the disk of the galaxy, (Clementini et al. 1992a, in preparation), using the relation found by Clementini et al. (1991), (hereafter CTM91), between [Fe/H] and the equivalent width of the Ca II K-line W‘(K). (2) A quantitative chemical abundance analysis of the ab type RR Lyrae (V29) in the globular cluster M4 has been performed using high resolution, high S/N spectroscopy. We obtain [Fe/H]=–1.3 ± 0.2 and the α– elements (Mg and Ti) are overabundant by 0.6 dex. These results are in good agreement with determinations from high resolution spectra of giants and blue horizontal branch stars (Clementini et al. 1992b, in preparation).

Type
Windows on the Instability Strip
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 335 - 336
Copyright
Copyright © Cambridge University Press 1993

References

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