The NASA Galaxy Evolution Explorer (GALEX) satellite has obtained simultaneous near-ultraviolet (NUV) and far-ultraviolet (FUV) light curves of the ROTSE-I Catalog RR Lyrae type ab variable star J143753.84+ 345924.8. A series of 38 GALEX Deep Imaging Survey observations well distributed in phase within the star's 0.56432 day period shows an AB = 4.9 mag variation in the FUV (1350-1750 Å) band and an AB = 1.8 mag variation in the NUV (1750-2750 A) band, compared with only a 0.8 mag variation in the broad, unfiltered ROTSE-I (≈4500-10,000 Å) band. These GALEX UV observations are the first to reveal a large RR Lyrae amplitude variation at wavelengths below 1800 A. 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 (0.57433 days), 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 = 0.2 mag in the GALEX NUV and ROTSE-I bands and to within 0.5 mag in the FUV. At all metallicities between solar and 1/100 solar, the Kurucz models predict 6-8 mag of variation at wavelengths between 1000 and 1700 Å. 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.
Bibliographical noteFunding Information:
GALEX is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for the construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. The grating, freedom window, and aspheric corrector were supplied by France. We acknowledge the dedicated team of engineers, technicians, and administrative staff from JPL/Caltech, Orbital Sciences Corporation, the University of California, Berkeley, Laboratoire d’Astrophysique de Marseille, and the other institutions who made this mission possible. Financial support for this research was provided by NASA grant NAS5-98034. This publication makes use of data products from 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. We are particularly grateful for the clarifications and improvements suggested by an anonymous referee.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science