Hydrodynamic models for the short-period, classical Cepheid, SU Cas

Authors

T. Aikawa, University of Nebraska-Lincoln
E. Antonello, Osservatorio Astronomico di Brera
Norman R. Simon, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

1987

Citation

Astron. Astrophys. 181,25-30 (1987).

Comments

Copyright 1987 European Southern Observatory

Abstract

Hydrodynamic models are constructed for the 1.95- day, classical Cepheid, SU Cas. The models cover three luminosities (479, 955 and 2239 L_ʘ) and a range of temperatures (6200 K ≤ T_e ≤ 6500 K), in line with observational and theoretical results from the work of previous authors. Taking the linear stability and stability of limiting pulsations of the models into consideration, it is shown that at 479 L_ʘ only the fundamental mode is possible; at 955 L_ʘ the first overtone mode is possible; at 2239 L_ʘ only the second overtone mode is possible. For stable limit cycles, the light and velocity curves are compared with observations by means of Fourier decomposition. The Fourier component ϕ₂₁ for SU Cas is apparently greater than that of other classical Cepheids that are supposed to be fundamental mode pulsators with similar periods. However, hydrodynamic models display values of ϕ₂₁ that do not differ with pulsation mode. We attribute this to a shortcoming in the F -mode models. On the other hand, these models seem to produce reliable values of ϕ₃₁ and of the first-order phase lag (Δϕ)₁. We discuss the pulsation of SUC as in the light of stellar evolution calculations, and summarize the evidence regarding its pulsation mode. We conclude that SU Cas is almost certainly not an F -mode pulsator, although a completely satisfactory overtone model has yet to be constructed.