On Metallicity And RR Lyrae Light Curves

Authors

• Norman R. Simon, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

5-15-1988

Citation

THE ASTROPHYSICAL JOURNAL, 328:747-754,1988 May 15

Comments

Copyright 1988 The American Astronomical Society. All rights reserved.

Abstract

Fourier decompositions are performed for the light curves of six RR_ab and 3 RR_c field stars. These are added to previous work to form a sample of 61 RR_ab and 12 RR_c pulsators. The RR_ab stars are divided into two groups-a short-period (SP) group with P < 0^d.575 and a long-period (LP) group with P > 0^d.575. The Fourier phase parameter ϕ₂₁ is found to fall off very regularly with decreasing metallicity among the SP stars, but this relationship disappears abruptly when one enters the LP group. A small sample of RR_ab stars from the globular cluster Ѡ Cen shows hints of a similar ϕ₂₁ -metallicity relation. No trend of ϕ₂₁ with metallicity is found for the RR_c field stars. We look for a kinematic difference between the SP and LP RR_ab samples, but none is apparent. Finally, we use published one-zone models and new linear nonadiabatic pulsation calculations to tentatively identify the ϕ₂₁-metallicity relation as an opacity effect. However, no explanation is found for the absence of such a relation among the long-period RR_ab stars.