2010PASP..122...17J

The results of extensive time-series photometry of a new variable star, 2MASS, are presented. The, observations (over 4000 individual measurements) were made over 23 nights between 2006 and 2007. To investigate the star's physical characteristics additional Strömgren photometric observations were made on another four nights in 2007 and 2009. Thirteen frequencies were found from a multifrequency analysis of the and photometry. All but two of the frequencies, (corresponding to the pulsation period of 0.0500071 day) and (0.0386898 day), have been identified as combination frequencies. The ratio of the two frequencies,, and their pulsation constants, and, are well matched with theoretical values of the fundamental and the first-overtone radial modes. But the phase shift of was estimated to be a negative value, in contrast to that of to be positive, suggesting that may be a nonradial mode. The period versus amplitude diagram shows that the star has pulsational properties similar to those of high-amplitude SX Phœnicis stars. We obtained its photometric properties from the Strömgren indices: a metal abundance of, an absolute magnitude of, a distance of in the direction of the Galactic anticenter from the Sun, and a vertical distance from the Galactic plane of. The tangential velocity of, which was estimated from the proper motion and the distance, gives us a hint that the star may have high-space motion. Considering these observational properties, we suggest that this new variable is a field SX Phœnicis-type star, although its metallicity value seems not to be low enough for matching the metallicity versus period relation. Future spectroscopic studies would be required to obtain the metallicity more accurately.