Equations of state and bump Cepheids

The paper presents results of calculations investigating the consequences of a number of recent advances in atomic physics for stellar pulsations, i.e., the Hummer-Mihalas-Dappen (HMD) equation of state and opacities generated with new atomic data (Seaton, 1987). The sensitivity of theoretical linear nonadiabatic (LNA) bump Cepheid calculations to the equation used in such calculations is examined. LNA periods, growth rates, and period ratios for a specified model grid were calculated using both the HMD and the Saha equations of state. The model grid is taken from Simon and Davis (1983), who used the Los Alamos equastion of state in their calculations. A comparison in terms of theoretical linear pulsation results can thus be made between three equations of state. 7 refs