Research Papers in Physics and Astronomy


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Published in The Astrophysical Journal 261:586-594, 1982. Copyright (c) 1982 The American Astronomical Society. Use by permission.


Fourier decompositions have been made of the light curves of a large sample of RR Lyrae field stars. The coefficients have been tabulated. Following the scheme of an earlier investigation of classical Cepheids, certain combinations of the low-order coefficients - φ21, R21, and φ31 - are plotted against period. The Bailey-type c pulsators stand out from the type ab stars, particularly on the R21 plot which is found to be a more sensitive discriminator of Bailey type than is the traditionally employed amplitude-period diagram. We compare the RR Lyrae plots of φ21, R21, and φ31 with those previously obtained for classical Cepheids. It is noted that, while the Cepheid plots display a tightly defined progression with period, reflecting the influence of a modal resonance, in the RR Lyrae case there is much more scatter. However, some evidence is shown to exist for a Cepheid-like progression appearing among the longer period RR Lyrae pulsators and culminating in the unique small-amplitude variable XZ Ceti. New observations will be required to confirm the reality of such a progression.

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