The Identification of RR Lyrae and Delta Scuti Stars from Variable GALEX Ultraviolet Sources

TL;DR

This study identifies and classifies RR Lyrae and delta Scuti stars in GALEX ultraviolet source catalogs, revealing new variables and demonstrating the utility of NUV-V color for metallicity and temperature diagnostics.

Contribution

It introduces a method to classify variable stars using NUV amplitudes and colors, and reports new variable stars not previously cataloged.

Findings

Identified 8 DSCT, 17 RRc, 1 RRd, and 84 RRab stars in GALEX catalogs.

NUV amplitude is about twice that in V-band, aiding low amplitude variable detection.

NUV-V color effectively distinguishes metallicity and temperature differences.

Abstract

We identify the RR Lyrae and delta Scuti (DSCT) stars in three catalogs of GALEX variable sources. The NUV amplitude of RR Lyrae stars is about twice that in V-band, so we find a larger percentage of low amplitude variables than catalogs such as Abbas et al (2014). Interestingly, the (NUV-V)_0 color is sensitive to metallicity and can be used to distinguish between variables of the same period but differing [Fe/H]. This color is also more sensitive to T_eff than optical colors and can be used to identify the red edge of the instability gap. We find 8 DSCT stars, 17 RRc stars, 1 RRd star and 84 RRab stars in the GALEX variable catalogs of Welsh et al (2005) and Wheatley et al (2008). We also classify 6 DSCT stars, 5 RRc stars and 18 RRab stars among the 55 variable GALEX sources identified as "stars" or RR Lyraes in the catalog of Gezari et al (2013). We provide ephemerides and light curves for the 26 variables that were not previously known.