Black Hole Blackbodies

Abstract

Many black-hole sources emit a substantial fraction of their luminosities in blackbody-like spectral components. It is usual to assume that these are produced in regions at least comparable in size to the hole's Schwarzschild radius, so that a measure of the emitting area provides an estimate of the black hole mass M. However there is then no guarantee that the source luminosity (if isotropic) obeys the Eddington limit corresponding to M. We show that the apparent blackbody luminosity L_sph and temperature T must obey the inequality L_sph < 2.3 10^44 (T/100 eV)^-4 erg s^-1 for this to hold. Sources violating this limit include ultrasoft AGN and some of the ultraluminous X-ray sources (ULXs) observed in nearby galaxies. We discuss the possible consequences of this result, which imply either super-Eddington or anisotropic emission in both cases. We suggest that the ultrasoft AGN are the AGN analogues of the ULXs.

4 pages, 1 figure; accepted for MNRAS Letters

References in corpus (6)

• Ultraluminous X-Ray Sources in External Galaxies
• Super-Eddington Fluxes from Thin Accretion Disks?
• Chandra Observations of "The Antennae" Galaxies (NGC 4038/39)
• The Fragmentation of Pre-enriched Primordial Objects
• The Ultra-luminous M81 X-9 source: 20 years variability and spectral states
• Spectral variability of Ultra Luminous Compact X-ray Sources in Nearby Spiral Galaxies

Cited by in corpus (15)

• Intermediate-Mass Black Holes
• Masses, Beaming and Eddington Ratios in Ultraluminous X-ray Sources
• A spectral-timing model for ULXs in the super-critical regime
• Spectral variability of ultraluminous X-ray sources
• Accretion Disk Spectra of the Ultra-luminous X-ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources
• A Variable Ultraluminous Supersoft X-ray Source in "The Antennae": Stellar-Mass Black Hole or White Dwarf?
• Eddington limit and radiative transfer in highly inhomogeneous atmospheres
• Slim Disks with Transition Regions and Applications to Microquasars and Narrow Line Seyfert 1 Galaxies
• Suzaku Observations of M82 X-1 : Detection of a Curved Hard X-ray Spectrum
• XMM Observations of an IXO in NGC 2276
• A Limit Relation between Black Hole Mass and H$\beta$ Width: Testing Super-Eddington Accretion in Active Galactic Nuclei
• XMM-Newton spectroscopy of high redshift quasars
• Spectral state transitions in Circinus ULX5
• The impact of precession on the observed population of ULXs
• An extreme Ultraluminous X-ray source X-1 in NGC 5055