2010ApJ...712L.169F -
Astrophys. J., 712, L169-L173 (2010/April-1)
Identification of the X-ray thermal dominant state in an ultraluminous X-ray source in M82.
FENG H. and KAARET P.
Abstract (from CDS):
The thermal dominant state in black hole binaries (BHBs) is well understood but rarely seen in ultraluminous X-ray sources (ULXs). Using simultaneous observations of M82 with Chandra and XMM-Newton, we report the first likely identification of the thermal dominant state in a ULX based on the disappearance of X-ray oscillations, low timing noise, and a spectrum dominated by multicolor disk emission with luminosity varying to the fourth power of the disk temperature. This indicates that ULXs are similar to Galactic BHBs. The brightest X-ray spectrum can be fitted with a relativistic disk model with either a highly super-Eddington (Ldisk/LEdd= 160) non-rotating black hole (BH) or a close to Eddington (Ldisk/LEdd∼ 2) rapidly rotating BH. The latter interpretation is preferred, due to the absence of such highly super-Eddington states in Galactic BHs and active galactic nuclei, and suggests that the ULX in M82 contains a BH of 200-800 solar masses with nearly maximal spin. On long timescales, the source normally stays at a relatively low flux level with a regular 62-day orbital modulation and occasionally exhibits irregular flaring activity. These thermal dominant states are observed during outbursts.
Abstract Copyright:
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Journal keyword(s):
accretion, accretion disks - black hole physics - X-rays: binaries - X-rays: individual: CXOM82 J095550.2+694047 = X41.4+60
Simbad objects:
5
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