A 106-d period in the nuclear source X-8 in M33
Astrophysics
2009-10-30 v1
Abstract
With an X-ray luminosity of about 10^39 erg/s, the source X-8 coincident with the optical center of M33 is the most luminous X-ray source in the Local Group. However, its nature remains a mystery. We present here new and archival ROSAT observations of X-8 spread over 6 years which show variability and a ~ 106-d periodicity. This implies that (most of) the emission from M33 X-8 arises from a single object, perhaps a binary system with a ~ 10 Msol black hole primary. We suggest that the companion is a giant orbiting with a ~ 10 day period, and that the observed modulation is ``super-orbital'', analogous to that seen in Cyg X-2 and X1820-30.
Cite
@article{arxiv.astro-ph/9710009,
title = {A 106-d period in the nuclear source X-8 in M33},
author = {G. Dubus and P. A. Charles and K. S. Long and P. J. Hakala},
journal= {arXiv preprint arXiv:astro-ph/9710009},
year = {2009}
}
Comments
17 pages, 3 postscript figures, LaTeX, uses aasms4.sty, accepted for publication in ApJ Letters