The Absolute Magnitude of RRc Variables From Statistical Parallax
Abstract
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 247 RRc selected from the All Sky Automated Survey (ASAS) 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 (CARRS). We find that M_(V,RRc) = 0.52 +/- 0.11 at a mean metallicity of [Fe/H] = -1.59. This is to be compared with previous estimates for RRab stars (M_(V,RRab) = 0.75 +/- 0.13 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 to be (W_pi, W_theta, W_z) = (10.9,34.9,7.2) km/s in the radial, rotational and vertical directions with dispersions (sigma_(W_pi), sigma_(W_theta), sigma_(W_z)) = (154.7, 103.6, 93.8) km/s. For the disk, we find (W_pi, W_theta, W_z) = (8.5, 213.2, -22.1) km/s with dispersions (sigma_(W_pi), sigma_(W_theta), sigma_(W_z)) = (63.5, 49.6, 51.3) km/s. Finally, we suggest that UCAC2 proper motion errors may be overestimated by about 25%
Keywords
Cite
@article{arxiv.1208.2689,
title = {The Absolute Magnitude of RRc Variables From Statistical Parallax},
author = {Juna A. Kollmeier and Dorota M. Szczygiel and Christopher R. Burns and Andrew Gould and Ian B. Thompson and George W. Preston and Christopher Sneden and Jeffrey D. Crane and Subo Dong and Barry F. Madore and Nidia Morrell and Jose L. Prieto and Stephen Shectman and Joshua D. Simon and Edward Villanueva},
journal= {arXiv preprint arXiv:1208.2689},
year = {2015}
}
Comments
Submitted to ApJ. 11 pages including 6 figures