Bizarre Hard X-ray Outbursts of Cygnus X-1

Abstract

A very high activity of Cygnus X-1 on 1999 April 19-21 was recorded by BATSE Large Area Detectors onboard the Compton Gamma-Ray Observatory. The peak luminosity was one order of magnitude higher than the normal luminosity of Cyg X-1. This fact can be critical for models of the hard state of Cyg X-1. The longest outburst lasted ~1000 s and demonstrated very unusual temporal and spectral behavior which indicates the presence of two emission components. One component is relatively soft (with a cutoff below 100 keV) and highly variable, and the other one is hard (extending above 100 keV), with much slower variability.

4 pages, 2 figures; version accepted to ApJ

References in corpus (5)

• Radiation mechanisms and geometry of Cygnus X-1 in the soft state
• Orbital, precessional and flaring variability of Cygnus X-1
• The Distribution of X-ray Dips with Orbital Phase in Cygnus X-1
• Small-scale inviscid accretion discs around black holes
• RXTE Observations of an Outburst of Recurrent X-ray Nova GS 1354-644

Cited by in corpus (11)

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• Periodic long-term X-ray and radio variability of Cygnus X-1
• Discovery of powerful millisecond flares from Cygnus X-1
• GRB070610 : A Curious Galactic Transient
• An intense state of hard X-ray emission of Cyg X-1 observed by INTEGRAL coincident with TeV measurements
• Particle transport in magnetized media around black holes and associated radiation
• Observations of giant outbursts from Cygnus X-1
• X-ray variability and energy spectra from NGC5408 X-1 with XMM-Newton
• Nonthermal processes and neutrino emission from the black hole GRO J0422+32 in a bursting state
• Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL