Is M82 X-1 Really an Intermediate-Mass Black Hole? X-Ray Spectral and Timing Evidence
Abstract
Ultraluminous X-ray sources (ULXs) with apparent luminosities up to hundreds of times the Eddington luminosity for a neutron star have been discovered in external galaxies. The existence of intermediate-mass black holes has been proposed to explain these sources. We present evidence for an intermediate-mass black hole in the ULX M82 X-1 based on the spectral features and timing (quasi-periodic oscillation [QPO]) properties of the X-radiation from this source. We revisited XMM-Newton and Rossi X-Ray Timing Explorer (RXTE) data for M82 X-1 obtained in 2001 and 1997 for XMM and RXTE, respectively. We show for these observations that the source is either in transition or in a high/soft state with photon spectral indices 2.1 and 2.7, respectively. We confirm the early determination of the QPO frequency ν~55 mHz in this source by Strohmayer & Mushotzky and identify this as the low-frequency QPO for the source. We apply a new method to determine the black hole mass of M82 X-1. The method uses the index-QPO low-frequency correlation that has been recently established in Galactic black hole candidates GRS 1915+105, XTE J1550-564, 4U 1630-47, and others. Using scaling arguments and the correlation derived from the consideration of Galactic black holes, we conclude that M82 X-1 is an intermediate black hole with a mass of the order of 1000 Msolar.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2004
- DOI:
- 10.1086/425736
- arXiv:
- arXiv:astro-ph/0409416
- Bibcode:
- 2004ApJ...614L.113F
- Keywords:
-
- Accretion;
- Accretion Disks;
- Black Hole Physics;
- Radiation Mechanisms: Nonthermal;
- Astrophysics
- E-Print:
- 7 pages and 3 figures. Accepted for publication in ApJ Letters, v.614, 2004, October 20