CCD Photometry of Candidate RR Lyrae Stars in the Sloan Digital Sky Survey

Abstract

We present unfiltered CCD photometry of a sample of 71 candidate RR Lyrae stars during 2003 and 2004, out of 148 candidate stars that were selected from Sloan Digital Sky Survey (SDSS) commissioning data by Ivezic and coworkers. We obtain light curves of 69 candidate stars and present a catalog of their positions, amplitudes, periods, types, and mean magnitudes. We confirm that the 69 stars are true RR Lyrae variables based on periods and light curves, for the first time for 41 of them. We identify 57 type ab, 11 type c, and 1 type d (double-mode) in our sample. The double-mode RR Lyrae star shows properties similar to globular cluster stars and are unlike field stars of the Galactic halo in the Petersen diagram. We also find one RR Lyrae star that is related to Pal 5 and recover another. In our sample, only two candidate stars do not have a reasonable light curve. We conclude that the ratio of contamination in our sample is less than ~8%, which shows that the criteria used by Ivezic and coworkers to select RR Lyrae stars from the SDSS two-epoch data are reliable.