Masses of the Double-Mode RR Lyrae Stars

We re-examine the double-mode RR Lyrae (RRd) mass determination using both new and previously existing linear pulsation models. The independently written Los Alamos (Cox, et al. 1983. Ap. J. 266, 94) and Aikawa (Aikawa and Simon 1983, Ap. J. 273, 346) pulsation codes both yield canonical values for the RRd masses, i.e., 0.55 Mʘ for 0o I clusters, and 0.65 Mʘ for 0o II clusters. These results are essentially independent of reasonable changes in helium abundance, the treatment of convection and the formulation of standard opacities. \u27We show that recent contrary results by Petersen (1990. preprint) are almost certainly due\u27 to the use of an adiabatic approximation and inappropriate metallicity. Given this, it is further argued that earlier disorepant results due to Kovacs (1985; Acta Astr. 35. 37) ought not to be given a high weight. Finally, we concur with Petersen\u27s (1990) assertion that the 0o I RRd masses could be increased provided that Population II metal opacities turn out to be very high