Thermal limit for spherical accretion and X-ray bursts

Journal Article · Sat Apr 01 04:00:00 EST 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156023· OSTI ID:6931963

Grindlay, J E

A mechanism is described whereby the rate of spherical accretion on a collapsed object and the resulting X-ray luminosity can be limited by thermal heating and evaporation of the accreting gas. The luminosity limit can be a factor of approx.100 below the corresponding Eddington limit. Steady accretion flow is not possible within a range above this limit, and X-ray bursts can be produced by accretion surges resulting from the cooling and collapse of a heated gas shell above a critical optical depth. The luminosity and approximate recurrence rate of the bursts from NGC 6624 and other burst sources may then be understood. A general model for bursters is proposed in which massive (approx.10--100 M/sub sun/) black holes, from massive stars and the cores of disrupted globular clusters, undergo supercritical spherical accretion in interstellar clouds. Both X-ray and ..gamma..-ray bursts are predicted to have similar hard X-ray (approx.200 keV) spectra, though high average accretion rates and central optical depths also yield a comparable luminosity at approx.5 keV from a Comptonized black body spectrum in the X-ray bursts and associated steady sources.

• Research Organization: Center for Astrophysics, Harvard College Observatory and Smithsonian Astrophysical Observatory
• OSTI ID: 6931963
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 221:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BASIC INTERACTIONS
BLACK HOLES
COMPTON EFFECT
COOLING
COSMIC GASES
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
EVAPORATION
FLUIDS
GASES
HEATING
INTERACTIONS
IONIZING RADIATIONS
LUMINOSITY
MATHEMATICAL MODELS
OPTICAL PROPERTIES
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RADIATIONS
RADIATIVE COOLING
SCATTERING
STAR ACCRETION
STAR CLUSTERS
STAR EVOLUTION
STAR MODELS
STELLAR WINDS
X RADIATION