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Session 31 - Black Holes.
Oral session, Monday, January 15
Corte Real, Hilton

[31.02] Soft Gamma-Ray Emission from the Galactic X-Ray Transient GRO J1655-40

P. Kaaret (Columbia U.), R. A. Kroeger, M. S. Strickman, J. E. Grove (Naval Research Laboratory), E. Ford (Columbia U.), D. Grabelsky (Northwestern), B. A. Harmon (NASA/MSFC), M. McConnell (U. New Hampshire)

We present an analysis of soft gamma-ray observations of the x-ray transient GRO J1655-40 made with OSSE. This galactic source has been observed to produce ``superluminal'' radio jets. Radio data indicate that we view the accretion disk edge on. OSSE detected emission in the 50-700 keV band during several observations of the target made during outbursts detected by BATSE in 1994 and 1995. The spectrum over this energy range is adequately described by a simple power law. There is no evidence for a thermal component or a high-energy exponential cutoff in the spectrum. The power spectrum of the soft gamma-ray emission shows no features and very little power at frequencies above 0.1 Hz. A possible interpretation of the absence of a thermal component in the spectrum and lack of high-frequency noise is that the accretion disk is obscured and that the soft gamma-ray emission observed originates in a hot extended corona.

This work was supported in part by NASA Grant NAG 5-2235.

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