Period-luminosity-color relations and pulsation modes of pulsating variable stars.
Abstract
The periods of 8 Scuti, RR Lyrae, dwarf Cepheid, and W Virginis variables have been investigated for their dependence on luminosity, color, mass, and pulsation modes. A maximum- likelihood method, which includes consideration of the observational errors in each coordinate, has been applied to obtain observational period-luminosity-color (P-L-C) relations. Hot and cool 8 Scuti stars show different values of the pulsation constant Q. Mean values of 0.022 + 0.001 and 0.030 + 0.001 days were derived for these two groups. On the radial pulsation hypothesis, the cool variables pulsate in the fundamental mode, while the hotter variables tend to pulsate in the first and second overtones. Analogous to RR Lyrae stars, the division into different pulsation modes seems to be determined by color. The RR Lyrae variables in several globular clusters are found to obey a P-L-C relation almost identical to theoretical relations. Mean absolute magnitudes differ from cluster to cluster, but are also in excellent agreement with mean absolute magnitudes deduced from the transition period in each cluster. SX Phe, a Population II dwarf Cepheid variable, lies on the extension of the RR Lyrae P-L-C relation. Periods of W Virginis stars also show a dependence on both luminosity and color. Our P-L-C relation also fits the 26-day variables. Finally, the coefficients of all the observational and theoretical relations are compared and discussed. Subject headings: Cepheids and W Virginis stars 8 Scuti stars - pulsation - RR Lyrae stars
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1975
- DOI:
- 10.1086/153794
- Bibcode:
- 1975ApJ...200..343B