Research Papers in Physics and Astronomy


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THE ASTROPHYSICAL JOURNAL, 420: 880-883, 1994 January 10.


Copyright 1994 The American Astronomical Society. All rights reserved.


Comparative linear nonadiabatic pulsation calculations are presented using the OPAL and Opacity Project opacities. The two sets of opacities include effects due to intermediate coupling and fine structure as well as new abundances. We used two mass luminosity (M - L) relations, one standard (BIT), and one employing substantial convective core overshoot (CO V). The two sets of opacities cannot be differentiated on the basis of the stellar pulsation calculations presented here. The BIT relation can model the beat and bump Cepheids with masses between 4 and 7 M ʘ while if the overshoot relation is used, masses between 2 and 6 M ʘ are required. In the RR Lyrae regime, we find the inferred masses of globular cluster RRd stars to be little influenced by the choice of OPAL or OP. Finally, the limited modeling we have done is not able to constrain the Cepheid M - L relation based upon period ratios observed in the beat and bump stars.