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Large-Amplitude Ultraviolet Variations in the RR Lyrae Star ROTSE-I J143753.84+345924.8

J. M. Wheatley·B. Y. Welsh·O. H. W. Siegmund·Y. I. Byun·S. Yi·Y. W. Lee·B. F. Madore·M. Viton·R. M. Rich·L. Bianchi·T. A. Barlow·J. Donas·K. Forster·P. G. Friedman·T. M. Heckman·P. N. Jelinsky·R. F. Malina·D. C. Martin·B. Milliard·P. Morrissey·S. G. Neff·D. Schiminovich·T. Small·A. S. Szalay·T. K. Wyder
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Abstract

The NASA Galaxy Evolution Explorer (GALEX) satellite has obtained simultaneous near and far ultraviolet light curves of the ROTSE-I Catalog RR Lyrae ab-type variable star J143753.84+345924.8. A series of 38 GALEX Deep Imaging Survey observations well distributed in phase within the star's 0.56432d period shows an AB=4.9mag variation in the far UV (1350-1750A) band and an AB=1.8mag variation in the near UV (1750-2750A) band, compared with only a 0.8mag variation in the broad, unfiltered ROTSE-I (4500-10000A) band. These GALEX UV observations are the first to reveal a large RR Lyrae amplitude variation at wavelengths below 1800A. We compare the GALEX and ROTSE-I observations to predictions made by recent Kurucz stellar atmosphere models. We use published physical parameters for the comparable period (0.57433d), well-observed RR Lyrae star WY Antliae to compute predicted FUV, NUV, and ROTSE-I light curves for J143753.84+345924.8. The observed light curves agree with the Kurucz predictions for [Fe/H]=-1.25 to within AB=0.2mag in the GALEX NUV and ROTSE-I bands, and within 0.5mag in the FUV. At all metallicities between solar and one hundredth solar, the Kurucz models predict 6-8mag of variation at wavelengths between 1000-1700A. Other variable stars with similar temperature variations, such as Cepheids, should also have large-amplitude FUV light curves, observable during the ongoing GALEX imaging surveys.

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J. M. Wheatley, B. Y. Welsh, O. H. W. Siegmund, Y. I. Byun, S. Yi, Y. W. Lee, B. F. Madore, M. Viton, R. M. Rich, L. Bianchi, T. A. Barlow, J. Donas, K. Forster, P. G. Friedman, T. M. Heckman, P. N. Jelinsky, R. F. Malina, D. C. Martin, B. Milliard, P. Morrissey, S. G. Neff, D. Schiminovich, T. Small, A. S. Szalay, T. K. Wyder. 2004-11-10. Large-Amplitude Ultraviolet Variations in the RR Lyrae Star ROTSE-I J143753.84+345924.8. https://doi.org/10.1086/422391

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