Observations of giant outbursts from Cygnus X-1

Abstract

We present interplanetary network localization, spectral, and time history information for 7 episodes of exceptionally intense gamma-ray emission from Cygnus X-1. The outbursts occurred between 1995 and 2003, with durations up to \~28000 seconds. The observed 15 - 300 keV peak fluxes and fluences reached 3E-7 erg /cm2 s, and 8E-4 erg / cm2 respectively. By combining the triangulations of these outbursts we derive an ~1700 square arcminute (3 sigma) error ellipse which contains Cygnus X-1 and no other known high energy sources. The outbursts reported here occurred both when Cyg X-1 was in the hard state as well as in the soft one, and at various orbital phases. The spectral data indicate that these outbursts display the same parameters as those of the underlying hard and soft states, suggesting that they represent another manifestation of these states.

arXiv comment27 pages, 9 figures. Revised version. Accepted for publication in the Astrophysical Journal, tentatively scheduled for October 20, 2003 Part 1

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• Unveiling the nature of six HMXBs through IR spectroscopy
• Episodic Transient Gamma-Ray Emission from the Microquasar Cygnus X-1
• XTE J1739-302 as a Supergiant Fast X-ray Transient
• Periodic long-term X-ray and radio variability of Cygnus X-1
• Gamma-ray observations of Cygnus X-1 above 100 MeV in the hard and soft states
• 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
• Spectral Evolution of weak bursts from SGR 1806-20 observed with INTEGRAL
• Viscous propagation of mass flow variability in accretion discs
• Nonthermal processes and neutrino emission from the black hole GRO J0422+32 in a bursting state
• Study of the Fast X-Ray Transient XTE J1901+014 Based on INTEGRAL, RXTE and ROSAT Data
• A year-long AGILE observation of Cygnus X-1 in hard spectral state
• Peculiar outbursts of an ultra luminous source likely signs of an aperiodic disc-wind
• INTEGRAL high energy detection of the transient IGR J11321-5311