Chemical composition of semi-regular variable giants^*

¹ GEPI, Observatoire de Paris-Meudon, 92125 Meudon Cedex, France
² Department of Astronomy and Astronomical Observatory, Odessa National University, T.G. Shevchenko Park, 65014 Odessa, Ukraine
³ Isaac Newton Institute of Chile, Odessa Branch, Ukraine e-mail: scan@deneb1.odessa.ua; serkor@skyline.od.ua
⁴ Canada-France-Hawaii Telescope, PO Box 65-1238, Mamalahoa Hwy, HI 96743, USA e-mail: martin@cfht.hawaii.edu

Received: 14 August 2006
Accepted: 4 December 2006

Abstract

Aims.The aim of this work was to derive chemical abundances in 5 stars that were previously reported to be SRd variable stars from the halo population, and, in particular, to check if manganese does show significant underabundance in our program stars similar to that of TY Vir, first detected by Luck & Bond.

Methods.Elemental abundances have been found through the LTE and NLTE analyses, applied to high-resolution () spectra.

Results.We have derived the abundances of 18 chemical elements in RX Vir, AB Leo, CK Vir, SV UMa, and TY Vir, and made the following conclusions.

Conclusions.RX Vir is a typical solar-like star. Its classification as a halo population SRd variable star should be ruled out. The remaining four stars of our program have chemical composition and fundamental parameters that confirm their status as metal-deficient halo giants. All studied SRd giants have relative-to-solar elemental abundances typical of the field halo stars of metallicity –1.8. There is only one exception, which is the relative manganese abundance. All SRd program stars show uniform [Mn/Fe] ratios that are typical of the stars with metallicity [Fe/H] . The reason for such a low manganese abundance in these stars is unknown.