RR lyrae variables in the inner halo. I. Photometry

I present V-band CCD photometry for a sample of 103 RR Lyrae variables selected from the General Catalogue of Variable Stars to lie in the inner halo of the Galaxy (3 kpc < R-GC < 6 kpc). I also describe a method for obtaining the mean apparent magnitude and the epoch at maximum light of an RR Lyrae star. The method requires as few as five photometric observations, and simulations demonstrate that the associated errors are relatively small (similar to 0.03 mag and similar to 0.03 days, respectively). I employ this method to derive the mean magnitudes and maximum light epochs of the 103 RR Lyrae stars observed. These stars were selected, based on their Galactic coordinates and original photographic photometry, to lie near their orbital tangent points, thus providing a sample well suited for measuring the rotational kinematics of the inner halo. Using interstellar reddenings from the literature and the observed mean V magnitudes, I derive distances for these stars and show that their actual locations in the Galaxy are indeed suitable for use in a kinematic study, despite the large zero-point errors in the survey photographic photometry. The results of the kinematic study will be presented in a separate paper.