2013ApJ...775...57K

We present the first definitive measurement of the absolute magnitude of RR Lyrae c-type variable stars (RRc) determined purely from statistical parallax. We use a sample of 242 RRc variables selected from the All Sky Automated Survey for which high-quality light curves, photometry, and proper motions are available. We obtain high-resolution echelle spectra for these objects to determine radial velocities and abundances as part of the Carnegie RR Lyrae Survey. We find that M_V, RRc_= 0.59±0.10 at a mean metallicity of [Fe/H] = -1.59. This is to be compared with previous estimates for RRab stars (M_V, RRab_= 0.76±0.12) and the only direct measurement of an RRc absolute magnitude (RZ Cephei, M_V, RRc_= 0.27±0.17). We find the bulk velocity of the halo relative to the Sun to be (W_π, W_θ, W_z) = (12.0, -209.9, 3.0) km/s in the radial, rotational, and vertical directions with dispersions (σ_Wπ, σ_Wθ, σ_Wz) = (150.4, 106.1, 96.0) km/s. For the disk, we find (W_π, W_θ, W_z) = (13.0, -42.0, -27.3) km/s relative to the Sun with dispersions (σ_Wπ, σ_Wθ, σ_Wz) = (67.7, 59.2, 54.9) km/s. Finally, as a byproduct of our statistical framework, we are able to demonstrate that UCAC2 proper-motion errors are significantly overestimated as verified by UCAC4.