On the observed disc temperature of accreting intermediate mass black holes

Abstract

Some ultraluminous X-ray sources in nearby galaxies show soft components resembling thermal disc emission. Calculations based on blackbody emission then indicate that the accreting black holes at the centres of these discs have masses of 100s to 1000s Msun. Establishing the existence of such intermediate mass black holes is of considerable importance so the assumptions and approximations lying behind blackbody spectral fits must be examined. We study here the basic assumption that the thermal emission is well-characterised by a multi-temperature blackbody spectrum. Since the opacity in the surface layers of a disc decreases at high energies the emergent spectrum is hardened. We compute the observed spectra from discs around a non-spinning 1000 Msun black hole and fit them over the XMM-Newton pn band with multi-colour disc models. The typical overall spectra hardening factor usually adopted for discs around stellar mass black hole (assuming an inclination of 60 deg and including relativistic effects for a non-spinning black hole) is found to be appropriate.

arXiv comment4 pages, 2 figs, to appear in MNRAS

References in corpus (19)

• Massive Black Holes as Population III Remnants
• Ultraluminous X-Ray Sources in External Galaxies
• The formation of massive black holes through collision runaway in dense young star clusters
• Black Hole Spin in X-Ray Binaries: Observational Consequences
• The Nature of Ultra-Luminous Compact X-Ray Sources in Nearby Spiral Galaxies
• Radiation mechanisms and geometry of Cygnus X-1 in the soft state
• Super-Eddington Fluxes from Thin Accretion Disks?
• Intermediate-Mass Black Holes
• X-ray Spectroscopic Evidence for Intermediate Mass Black Holes: Cool Accretion Disks in Two Ultra--Luminous X-ray Sources
• On the interpretation of the multicolour disc model for black hole candidates
• Discovery of X-ray QPOs from an Ultra-luminous X-ray Source in M82: Evidence Against Beaming
• Population X: Are the super-Eddington X-ray sources beamed jets in microblazars or intermediate mass black holes?
• Complete RXTE Spectral Observations of the Black Hole X-ray Nova XTE J1550-564
• Revealing a Cool Accretion Disk in the Ultraluminous X-ray Source M81 X-9 (Holmberg IX X-1): Evidence for an Intermediate Mass Black Hole
• Probable intermediate mass black holes in NGC4559: XMM-Newton spectral and timing constraints
• A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1
• ASCA observations of the nearby galaxies Dwingeloo 1 and Maffei 1
• The spectra of accretion discs in low-mass X-ray binaries
• XMM-Newton Spectroscopy of Bright ULX Sources in the Antennae Galaxies (NGC 4038/4039)

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• Radio observations of extreme ULXs: revealing the most powerful ULX radio nebula ever or the jet of an intermediate-mass black hole?
• Radio and X-ray Properties of Relativistic Beaming Models for Ultra-Luminous X-ray Sources
• Non-LTE Spectra of Accretion Disks Around Intermediate-Mass Black Holes
• Present Evidence for Intermediate Mass Black Holes in ULXs and Future Prospects
• X-ray spectral cut-off and the lack of hard X-ray emission from two ultraluminous X-ray sources M81 X-6 and Holmberg IX X-1
• Black hole mass estimates from soft X-ray spectra
• Broadband X-ray spectral analysis of the ULX NGC 1313\,X-1 using JeTCAF: Origin of the ULX bubble