A high-velocity bulge RR Lyrae variable on a halo-like orbit
Abstract
We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR), which has the unusual radial velocity of -372 +- 8 km/s and true space velocity of -482 +- 22 km/s relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l,b)=(3,-2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.
Keywords
Cite
@article{arxiv.1506.02664,
title = {A high-velocity bulge RR Lyrae variable on a halo-like orbit},
author = {Andrea Kunder and R. Michael Rich and Keith Hawkins and Radek Poleski and Jesper Storm and Christian I. Johnson and Juntai Shen and Zhao-Yu Li and Maria Jose Cordero and David M. Nataf and Giuseppe Bono and Alistair R. Walker and Andreas Koch and Roberto De Propris and Andrzej Udalski and Michal K. Szymanski and Igor Soszynski and Grzegorz Pietrzynski and Krzysztof Ulaczyk and Lukasz Wyrzykowski and Pawel Pietrukowicz and Jan Skowron and Szymon Kozlowski and Przemyslaw Mroz},
journal= {arXiv preprint arXiv:1506.02664},
year = {2015}
}
Comments
accepted to ApJ Letters