On the Evolutionary State of β Cephei Stars.

Abstract

view Abstract Citations (38) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Evolutionary State of β Cephei Stars. Stothers, Richard Abstract An attempt is made to explain the Cephei variables as non-rotating stars undergoing radial oscillations, on the basis of their relatively low observed rotational velocities and the period analyses by van Hoof. Arguments based on the central condensation and on the time scale of evolution vis-a'-vis their observed numbers indicate that these B0.5-B2 giants are in the hydrogen-burning phase. Model sequences are constructed for stars of 15 and 20 Mo to the end of hydrogen burning. The pulsational characteristics are then obtained by perturbing the stable models in the usual adiabatic approximation. The results show that, at some central hydrogen abundance which is higher for the lower masses, the periods and their ratios may be accounted for. Ideally, these quantities imply a unique mass and mean molecular weight for each observed star on the H-R diagram, but comparison of theory and observation gives at present merely a mass range of 10-20 M0 and probably a "normal" chemical composition. At any rate, the of evolution of main-sequence O9-Bi stars across the instability strip seems to be correct. Uncertainties in the semiconvective theory of massive stars would appear to be irrelevant since the quasi-stable zone has almost no effect on the pulsational eigenfrequencies. Several lines of observational eyidence tend to confirm the theoretical results that p Cephei stars of lower mass fall closer to the initial main sequence. The Wolf-Rayet objects form an apparent extension of the instability strip to higher masses (0 sta?s). Publication: The Astrophysical Journal Pub Date: February 1965 DOI: 10.1086/148154 Bibcode: 1965ApJ...141..671S full text sources ADS | data products SIMBAD (2)