A spectrophotometric comparison of the physical properties of classical Cepheids and nonvariable supergiants and bright giants


Spectrophotometric observations using 30 A resolution in the wavelength range 3408-5910 Å have been obtained for nine classical Cepheids with log P (days) from 0.29 to 1.43 over several phases and for 14 F, G, and K spectral-type supergiants and bright giants. The observations were obtained in order to make an empirical comparison of the physical properties of the Cepheids and the nonvariables which have similar spectral types. Flux distributions for all stars were normalized to 4700 Å and corrected for interstellar reddening. The observed flux distributions are tabulated for all observations. The nonvariable stars were compared to existing models, and significant deviations between observations and models were found for wavelengths between 3408 and 4600 Å over a wide temperature range. Strengths of strongest absorption features were determined from the intrinsic flux distributions, but no significant differences were found between the two types of stars. Ratios of intrinsic flux distributions show that α Per matched δ Cep and η Aql near maximum within the errors of measurement. At other phases of these two Cepheids their continua can generally be matched by that of a nonvariable star to within ±0.1 spectral types. However, real differences remain at most observed phases which do not appear to be due entirely to luminosity differences. Similar results were found for DT Cyg, T Vul, and X Cyg.

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© 1979 The American Astronomical Society.

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Journal Title

The Astrophysical Journal Supplement Series