Distance Scale Zero-Points from Galactic RR Lyrae Star Parallaxes
Abstract
We present new absolute trigonometric parallaxes and proper motions for seven Pop II variable stars: five RR Lyr variables; RZ Cep, XZ Cyg, SU Dra, RR Lyr, UV Oct; and two type 2 Cepheids; VY Pyx and {\kappa} Pav. We obtained these results with astrometric data from Fine Guidance Sensors, white-light interfer- ometers on Hubble Space Telescope. We find absolute parallaxes in milliseconds of arc: RZ Cep, 2.12\pm0.16 mas; XZ Cyg, 1.67\pm0.17 mas; SU Dra, 1.42\pm0.16 mas; RR Lyr, 3.77\pm0.13 mas; UV Oct, 1.71\pm0.10 mas; VY Pyx, 6.44\pm0.23 mas; and {\kappa} Pav, 5.57\pm0.28 mas; an average {\sigma}{\pi}/{\pi} = 5.4%. With these parallaxes we compute absolute magnitudes in V and K bandpasses corrected for interstellar extinction and Lutz-Kelker-Hanson bias. Using these RRL absolute magnitudes, we then derive zero-points for MV -[Fe/H] and MK -[Fe/H]-Log P relations. The technique of reduced parallaxes corroborates these results. We employ our new results to determine distances and ages of several Galactic globular clusters and the dis- tance of the LMC. The latter is close to that previously derived from Classical Cepheids uncorrected for any metallicity effect, indicating that any such effect is small. We also discuss the somewhat puzzling results obtained for our two type 2 Cepheids.
Cite
@article{arxiv.1109.5631,
title = {Distance Scale Zero-Points from Galactic RR Lyrae Star Parallaxes},
author = {G. Fritz Benedict and Barbara E. McArthur and Michael W. Feast and Thomas G. Barnes and Thomas E. Harrison and Jacob L. Bean and John W. Menzies and Brian Chaboyer and Luca Fossati and Nicole Nesvacil and Horace A. Smith and Katrien Kolenberg and C. D. Laney and Oleg Kochukhov and Edmund P. Nelan and D. V. Shulyak and Denise Taylor and Wendy L. Freedman},
journal= {arXiv preprint arXiv:1109.5631},
year = {2015}
}
Comments
Accepted by the Astronomical Journal