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Title:
Recent Results from the Compton Gamma Ray Observatory
Authors:
Shrader, C. R.; Gehrels, N.
Publication:
Publications of the Astronomical Society of the Pacific, v.107, p.606 (PASP Homepage)
Publication Date:
07/1995
Origin:
PASP; KNUDSEN
PASP/ApJ Keywords:
X-RAYS: GENERAL, X-RAYS: BURSTS
DOI:
10.1086/133600
Bibliographic Code:
1995PASP..107..606S

Abstract

A selection of recent scientific findings from the Compton Gamma Ray Observatory is presented. In gamma-ray burst astrophysics, notable is the dramatic confirmation that bursts are isotropic but spatially inhomogeneous in their distribution. They exhibit temporal effects consistent with a time dilation as expected for a cosmologically distributed population, however alternate explanations cannt be ruled out. Also notable is the detection of delayed, nonthermal high-energy (MeV and GeV) gamma-ray emission possibly indicating that particle acceleration lasts long after the prompt emission. In active galactic nuclei (AGN) research, a new class of objects the gamma-ray blazars has been identified and a possible additional subclass of "MeV bump" quasars has emerged as well. Both of these AGN subclasses emit the bulk of their bolometric luminosity above of ~1 MeV. Gamma-ray bright Seyfert galaxies exhibit spectra which cut off at "100 keV indicative of thermal emission from plasma near the origin of the diffuse X-ray background. The detection of nuclear emission lines from 57Co in SN 1987A, 44Ti in Cas A, and the mapping of emission from 26Al along the galactic plane all have important implications for our understanding of nucleosynthesis and supernova dynamics. Monitoring of the Galactic Center electron-positron annihilation source have failed to reveal any dramatic variability episodes as have been reported in the past by some previous experiements, and a model consisting of a bulge component and a disk component, has begun to emerge. A dramatic increase in the number of known radio pulsars with gamma-ray emission, from 2 to 7, and gamma-ray light curves of unprecedented detail have provided tremendous insight into pulsar research. Nearly uninterrupted daily monitoring of a number of accretion-driven X-ray pulsars has provided an unprecedented view of their torque histories. A transition from spin-up to a spin-down state of GX 1+4 has recently been documented. Orbital solutions for the binary systems OAO 1657=415 and A 0535+26 have been derived, and for A 0535+26 a cyclotron absorption feature, suggestive of magnetic field strengths of >10^13 gauss has been detected. The study of X-ray novae, which thrived in the late 1970s has experienced a rejuvenation of significant proportions as a result of the Compton Gamma Ray Observatory's all-sky monitoring capabilities and programmatic flexibility. (SECTION: Invited Review Paper)

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