RR Lyrae in Draco dSph

The data were obtained with the Fred Lawrence Whipple Observatory 1.2m telescope on Mount Hopkins, Arizona, between 1998 August 19 and 1999 June 20, over 22 nights, over a period of 10 months, covering a 22'x22' field centered at {alpha}=17h19m57.5s, {delta}=57{deg}50'05" (J2000.0). The analysis of the BVI images produced 163 variable stars, 146 of which were RR Lyrae: 123 RRab, 16 RRc, 6 RRd, and one RR12.

The other variables include a SX Phe star, four anomalous Cepheids, and a field eclipsing binary. Using the short distance scale statistical parallax calibration of Gould & Popowski (1998ApJ...508..844G) and 94 RRab stars from our field, we obtain a distance modulus of (m-M)_0_=19.40+/-0.02(stat)+/-0.15(syst)mag for Draco, corresponding to a distance of 75.8+/-0.7(stat)+/-5.4(syst)kpc. By comparing the spread in magnitudes of RRab stars in B, V, and I, we find no evidence for internal dust in the Draco dwarf spheroidal galaxy.