Detailed Atmosphere Model Fits to Disk-Dominated ULX Spectra

Abstract

We have chosen 6 Ultra-Luminous X-ray sources from the {\it XMM-Newton} archive whose spectra have high signal-to-noise and can be fitted solely with a disk model without requiring any power-law component. To estimate systematic errors in the inferred parameters, we fit every spectrum to two different disk models, one based on local blackbody emission (KERRBB) and one based on detailed atmosphere modelling (BHSPEC). Both incorporate full general relativistic treatment of the disk surface brightness profile, photon Doppler shifts, and photon trajectories. We found in every case that they give almost identical fits and similar acceptable parameters. The best-fit value of the most interesting parameter, the mass of the central object, is between 23 and 73 M$_\sun$ in 5 of the 6 examples. In every case, the best-fit inclination angle and mass are correlated, in the sense that large mass corresponds to high inclination. Even after allowing for this degeneracy, we find that, with $\gtrsim 99.9$ formal statistical confidence, 3 of the 6 objects have mass $\gtrsim 25 M_\sun$; for the other 3, these data are consistent with a wide range of masses. A mass greater than several hundred $M_\sun$ is unlikely for the 3 best-constrained objects. These fits also suggest comparatively rapid black hole spin in the 3 objects whose masses are relatively well-determined, but our estimate of the spin is subject to significant systematic error having to do with uncertainty in the underlying surface brightness profile.

22 pages, 3 figures, accepted by ApJ

References in corpus (26)

• Ultraluminous X-Ray Sources in External Galaxies
• Active Galactic Nuclei as scaled-up Galactic black holes
• The Nature of Accreting Black Holes in Nearby Galaxy Nuclei
• The Nature of Ultra-Luminous Compact X-Ray Sources in Nearby Spiral Galaxies
• Production of Intermediate-Mass Black Holes in Globular Clusters
• Super-Eddington Fluxes from Thin Accretion Disks?
• Multi-Temperature Blackbody Spectrum of a Thin Accretion Disk around a Kerr Black Hole: Model Computations and Comparison with Observations
• X-ray Spectroscopic Evidence for Intermediate Mass Black Holes: Cool Accretion Disks in Two Ultra--Luminous X-ray Sources
• Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin Evolution
• Relativistic Accretion Disk Models of High State Black Hole X-ray Binary Spectra
• Distances to Nearby Galaxies in Sculptor
• Discovery of X-ray QPOs from an Ultra-luminous X-ray Source in M82: Evidence Against Beaming
• A Grid of Relativistic, non-LTE Accretion Disk Models for Spectral Fitting of Black Hole Binaries
• Magnetically Driven Accretion Flows in the Kerr Metric IV: Dynamical Properties of the Inner Disk
• XMM-Newton Archival Study of the ULX Population in Nearby Galaxies
• Quasi-Periodic Variability in NGC 5408 X-1
• Chandra X-ray Observations of the Spiral Galaxy M81
• 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
• Chandra observations of five ultraluminous X-ray sources in nearby galaxies
• Do Ultraluminous X-ray Sources Really Contain Intermediate-mass Black Holes?
• Photon Bubbles and the Vertical Structure of Accretion Disks
• On the Soft Excess in the X-ray Spectrum of Cir X-1: Revisitation of the Distance to Cir X-1
• An XMM-Newton view of M101: I. The luminous X-ray source population
• A photon breeding mechanism for the high-energy emission of relativistic jets
• Elemental Abundances of Nearby Galaxies through High Signal-to-Noise XMM-Newton Observations of ULXs
• Non-LTE Spectra of Accretion Disks Around Intermediate-Mass Black Holes

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• Transition to the disk dominant state of a new ultraluminous X-ray source in M82
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• Broad and Luminous [OIII] and [NII] in Globular Cluster ULXs
• A comparative analysis of standard accretion disks spectra: an application to Ultraluminous X-ray Sources
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