Multiwavelength Observations of the Runaway Binary HD 15137

M. Virginia McSwain (1), Michael De Becker (2), Mallory S. E. Roberts (3), Tabetha S. Boyajian (4), Douglas R. Gies (4), Erika D. Grundstrom (5), Christina Aragona (1), Amber N. Marsh (1), Rachael M. Roettenbacher (1)

(1) Lehigh University, (2) Institut d'Astrophysique et Geophysique, Universite de Liege, (3) Eureka Scientific, Inc., (4) Georgia State University, (5) Vanderbilt University

HD 15137 is an intriguing runaway O-type binary system that offers a rare opportunity to explore the mechanism by which it was ejected from the open cluster of its birth. Here we present recent blue optical spectra of HD 15137 and derive a new orbital solution for the spectroscopic binary and physical parameters of the O star primary. We also present the first XMM-Newton observations of the system. Fits of the EPIC spectra indicate soft, thermal X-ray emission consistent with an isolated O star. Upper limits on the undetected hard X-ray emission place limits on the emission from a proposed compact companion in the system, and we rule out a quiescent neutron star in the propellor regime or a weakly accreting neutron star. An unevolved secondary companion is also not detected in our optical spectra of the binary, and it is difficult to conclude that a gravitational interaction could have ejected this runaway binary with a low mass optical star. HD 15137 may contain an elusive neutron star in the ejector regime or a quiescent black hole with conditions unfavorable for accretion at the time of our observations.

Reference: AJ, 2010, in press
Status: Manuscript has been accepted