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Paper: HADS, multiple periods, period changes and the PL Relation
Volume: 292, Interplay of Periodic, Cyclic and Stochastic Variability in Selected Areas of the H-R Diagram
Page: 203
Authors: Laney, C. D.; Joner, M.; Rodriguez, E.
Abstract: High-Amplitude Delta Scuti stars (dwarf Cepheids) typically have one or two radial modes with stable amplitudes, but there are few real `clockwork stars'. Periods can change abruptly, and apparently smooth trends in period changes can alter or reverse abruptly. Interaction terms complicate analysis in double-mode stars, and two stars in our sample turned out to have previously unknown binary companions. AI Vel and RY Lep appear to have low-level nonradial modes present as well as the dominant radial mode(s). In RY Lep, it appears that the amplitude of the possible nonradial mode may vary considerably with time. Data for the three double-mode dwarf Cepheids studied so far do not support the idea that the fundamental mode is necessarily more sinusoidal than the first overtone. This suggests that caution is advisable in using skewness to decide whether a monoperiodic HADS is a fundamental pulsator. Nonetheless, reliable BW radii and luminosities can be derived for most dwarf Cepheids, and the resulting PR (and hence PL) relation appears to be an extension of the PR (and PL) relations for classical Cepheids.
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