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Session 81 - Variable Cool and Late Type Stars.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[81.13] A Luminosity-[Fe/H] Relation for RR Lyrae Stars Derived from Fourier Parameters

C. M. Clement (U. Toronto)

Simon and Clement(1993, ApJ 410, 526) have used the technique of Fourier decomposition of light curves to determine masses, luminosities and temperatures for Bailey c type RR Lyrae (RRc) variables. In an analysis of photographic data for RRc stars in six galactic globular clusters (three of Oosterhoff type I and three of type II) they found that mean masses and luminosities increase and mean temperatures decrease with decreasing metal abundance. An analysis of CCD observations of RRc stars in seven globular clusters (three of Oosterhoff type I and four of type II) confirms Simon and Clement's earlier result. From this, we can derive an M_V - [Fe/H] relation. Based on the the metallicity scale of Zinn (1985, ApJ 293, 424), this relationship is M_V=0.27[\rmFe/H]+0.97. If the metallicity scale of Jurcsik (1995, Acta A, 45, 653) is adopted instead, the relationship is M_V=0.19[\rmFe/H]+0.82. The absolute magnitudes derived from these two relationships are brighter than those derived from M_V - [Fe/H] relations whose zero points are calibrated by statistical parallaxes (Carney et al. 1992, ApJ 386, 663) or by the Baade-Wesselink method (Kovács and Jurcsik 1996, ApJL 466, 17).

Program listing for Wednesday