恒星物理研究组知识库

By using four different frozen-convection approximations, we investigate nonadiabatic radial pulsations for a 9 M. and a 2 M. stellar model, which represent, respectively, the Cepheid and delta Scuti variables, and we compare the characteristics of the pulsations. We find that the periods of the pulsation modes can differ as much as 6% for the 9 M, model and a small amount for the 2 M, model. The locations of the pulsation instability strips produced by the four frozen-convection approximations are significantly different from each other, as well as the eigenfunctions and work integrals. It is found that the approximation L-C'= 0 restrains the driving feature at the bottom of the convection zone in the quasi-adiabatic stellar interior and then gives rise to the red edge of the instability strip, while the approximations delta F-C = 0 and delta L-C = 0 result in the correct locations of the blue edges of the instability strips that are in good agreement with the observations. We conclude that each of the four frozen-convection approximations may describe some aspects of the convection-pulsation interaction, but none of them can be a complete solution of the problem. Based on considerations of the timescales of the pulsation and response time of the convection, we suggest that a combination of proper frozen-convection approximations may be a good measure of the nonadiabatic stellar pulsations.