BATSE Soft Gamma-Ray Observations of GROJ0422+32

Abstract

We report results of a comprehensive study of the soft gamma-ray (30 keV to 1.7 MeV) emission of GROJ0422+32 during its first known outburst in 1992. These results were derived from the BATSE earth-occultation database with the JPL data analysis package, EBOP (Enhanced BATSE Occultation Package). Results presented here focus primarily on the long-term temporal and spectral variability of the source emission associated with the outburst. The light curves with 1-day resolution in six broad energy-bands show the high-energy flux (>200 keV) led the low-energy flux (<200 keV) by ~5 days in reaching the primary peak, but lagged the latter by ~7 days in starting the declining phase. We confirm the "secondary maximum" of the low-energy (<200 keV) flux at TJD 8970-8981, ~120 days after the first maximum. Our data show that the "secondary maximum" was also prominent in the 200-300 keV band, but became less pronounced at higher energies. During this 200-day period, the spectrum evolved from a power-law with photon index of 1.75 on TJD 8839, to a shape that can be described by a Comptonized model or an exponential power law below 300 keV, with a variable power-law tail above 300 keV. The spectrum remained roughly in this two-component shape until ~9 November (TJD 8935) and then returned to the initial power-law shape with an index of ~2 until the end of the period. The correlation of the two spectral shapes with the high and low luminosities of the soft gamma-ray emission is strongly reminiscent of that seen in Cygnus X-1. We interpret these results in terms of the Advection Dominated Accretion Flow (ADAF) model with possibly a "jet-like" region that persistently produced the non-thermal power-law gamma rays observed throughout the event.

40 pages total, including 10 figures and 2 tables

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Cited by in corpus (7)

• The Burst and Transient Source Experiment (BATSE) Earth Occultation Catalog of Low-Energy Gamma-Ray Sources
• Correlation between Hard X-ray Peak Flux and Soft X-ray Peak Flux in the Outburst Rise of Low Mass X-ray Binaries
• The INTEGRAL view on Black Hole X-ray Binaries
• Gamma-Ray Spectral State Transitions of GRO J1719-24
• Nonthermal processes and neutrino emission from the black hole GRO J0422+32 in a bursting state
• A model for the polarization of the high-energy radiation from accreting black holes: the case of XTE J1118+480
• Spectral Properties of Black Holes in Gamma Rays