Abstract
view Abstract Citations (16) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Stellar Pulsation. V. a. Semitheoretical Period-Luminosity Relation for Cepheids with Radiative Envelopes. Cox, John P. Abstract Cepheid instability is assumed to occur in a star when the phase lag in the emitted flux is near 7r/2 radians. Supposing the phase lag to result from the partial ionization of He+, a period-luminosity (ll-L) relation for cepheids is derived on the basis of purely radiative envelope models. The ll-L relation agrees with the empirical one for classical cepheids in the range 0.4 < II (days) < 86 when a semiempirical mass-luminosity relation is adopted. Physical arguments suggest that radiative envelope models should apply to cepheids with II < 6 days. This is approximately the period below which the ll-L relation of Paper IV (Cox and ), based on convective envelope models, began to deviate from the empirical relation. In contrast to the results of Paper IV, the zero point of the present ll-L relation depends somewhat on the helium abundance. The dependence of the ll-L relation on the opacity law and on the assumed relation between mass and luminosity is discussed. Adopting I = 1.25 Mo for the population II cepheids leads to a ll-L relation for these stars which is approximately parallel to, and lies 1m2 below, the classical cepheid curve. It is suggested that the finite width of the region of cepheid instability may be explicable, in part, by the existence of a range of values of the phase lag for which a star evolving with constant mass and luminosity will be pulsationally unstable. This interpretation is not inconsistent with the available observations. Publication: The Astrophysical Journal Pub Date: July 1959 DOI: 10.1086/146717 Bibcode: 1959ApJ...130..296C full text sources ADS | Related Materials (3) Part 1: 1955PhDT.........1W Part 2: 1956AnAp...19..142W Part 3: 1958ApJ...127..561C
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