The Antennae Ultraluminous X-Ray Source, X-37, Is A Background Quasar
Abstract
In this paper we report that a bright, X-ray source in the Antennae galaxies (NGC 4038/9), previously identified as an ultra-luminous X-ray source, is in fact a background quasar. We identify an isolated infrared and optical counterpart within 0.3+/-0.5 arcseconds the X-ray source X-37. After acquiring an optical spectrum of its counterpart, we use the narrow [OIII] and broad H_alpha emission lines to identify X-37 as a quasar at a redshift of z=0.26. Through a U, V, and K_s photometric analysis, we demonstrate that most of the observable light along this line of sight is from the quasar. We discuss the implications of this discovery and the importance of acquiring spectra for optical and IR counterparts to ULXs.
Cite
@article{arxiv.astro-ph/0509143,
title = {The Antennae Ultraluminous X-Ray Source, X-37, Is A Background Quasar},
author = {D. M. Clark and M. H. Christopher and S. S. Eikenberry and B. R. Brandl and J. C. Wilson and J. C. Carson and C. P. Henderson and T. L. Hayward and D. J. Barry and A. F. Ptak and E. J. M. Colbert},
journal= {arXiv preprint arXiv:astro-ph/0509143},
year = {2009}
}
Comments
11 pages, 3 Postscript figures, accepted by ApJL