Abstract
We present the results of a 4 year photometric study of the high-amplitude δ Scuti (HADS) star UY Camelopardalis. Analysis of the available data from 1985 to 2003 shows that UY Cam is monoperiodic. Fourier solutions for individual data sets do not reveal period changes in the star. Although forced parabolic fits to the O-C residuals indicate a measurable period change, the distribution of the data points in the O-C diagram and the deviations between fits and observations suggest that the existence of the period change still has not been established. We demonstrate the presence of amplitude variations from cycle to cycle and on longer timescales. The pulsation amplitude seemed to change from 1985 to the 2000s, but it remained constant in 2000–2003. UY Cam is located in the upper portion of the δ Scuti instability region. Its photometric properties and estimated physical parameters reveal that UY Cam is an interesting object in terms of its poor metallicity, long period, high luminosity, low surface gravity, and large radius among the HADS stars. UY Cam could be a younger (0.7 ± 0.1 Gyr) Population I HADS star with low metal abundance (Z = 0.004) evolving on its post–main-sequence shell hydrogen burning evolutionary phase. UY Cam intervenes among the Population I/II HADS and type c RR Lyrae variables. These characteristics suggest the star to be an analog of HADS, SX Phoenicis, and RRc variables.
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