Self-correlation Studies of RV Tauri
Variables and Related Objects
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John R. Percy
Farisa Mohammed
Department
of Astronomy and Astrophysics, University of Toronto, Toronto, Ontario, Canada
Received
August 2003; revised August 2004
Abstract RV Tauri (RVT) variables are old,
low-mass, yellow supergiant pulsating variable stars whose light curves show
alternating deep and shallow minima. They are related to Population II Cepheid
(CW) variables and to yellow semiregular (SRd) variables. We describe the
results of self-correlation analysis of a large body of visual photometry of 9
bright RVT and SRd variables, namely AG Aur, AV Cyg, SU Gem, AC Her, SX Her, TT
Oph, UZ Oph, TX Per, and V Vul. Self-correlation analysis, which probes the
cycle-to-cycle behavior of a variable, averaged over a dataset, has proven to
be a useful tool for investigating these stars, because their classification is
actually based on their cycle-to-cycle behavior. Our results are consistent
with those of our analysis of RVT and CW variables in the Large Magellanic
Cloud (Percy, Hosick, and Leigh 2003), and support the view that the RV Tauri
phenomenon has two dimensions: (i) the relative depths of the primary and
secondary minima, and (ii) the number of cycles over which the alternating
minima correlate. If the RVT phenomenon is due to the presence of two pulsation
modes, then these dimensions are equivalent to: (i) the relative amplitudes of
the two modes, and (ii) the closeness of the ratio of the pulsation periods to
2:1. There is therefore a “spectrum” of behavior from CW to RVT to SRd,
depending on the values of these two parameters.
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