Hard X-Ray Variability in M82: Evidence for a Nascent Active Galactic Nucleus?
Abstract
We report on the detection of hard (2-10 keV) X-ray variability in the starburst galaxy M82 over the course of nine ASCA observations. Long-term variability occurred on a timescale of days, with a change in flux by a factor of up to ~4, corresponding to a point-source luminosity of L2-10 keV~6×1040 ergs s-1. Short-term variability with an amplitude of ~1.4 on a timescale of hours was observed during the longest observation. This demonstrates that a large fraction of the hard X-ray emission of M82 (depending on the flux state) is from a compact region and is probably due to an accreting source. The 2-10 keV luminosity of the source is a lower limit to its Eddington luminosity, implying a black hole mass of at least ~460 Msolar or a mass intermediate to that of normal active galactic nuclei and stellar-mass black hole candidates.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1999
- DOI:
- 10.1086/312032
- arXiv:
- arXiv:astro-ph/9903372
- Bibcode:
- 1999ApJ...517L..85P
- Keywords:
-
- GALAXIES: INDIVIDUAL: MESSIER NUMBER: M82;
- GALAXIES: STARBURST;
- X-RAYS: GALAXIES;
- Galaxies: Individual: Messier Number: M82;
- Galaxies: Starburst;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- 10 pages with 4 embedded figures, accepted for publication in ApJ Letters