OSSE Observations of NGC 4151
GEORGE MASON UNIV FAIRFAX VA
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We report results of a two-week observation of the Seyfert galaxy NGC 4151 with the Oriented Scintillation Spectrometer Experiment OSSE instrument on the Compton Gamma Ray Observatory GRO. The source had a very soft spectrum which is best represented by a broken power law or Sunyaev-Titarchuk thermal Comptonization model. It can be characterized by an exponential shape with an e-folding energy of 39 plus or minus 2 keV in the energy range 65 - 300 keV, and an intensity at 100 keV of 2.33 plus or minus 0.05 x 10 exp -5 photons sq cm s exp -1 keVexp -1. Source intensity variability of 25 was observed during the 14 days of our observations no significant change in spectral shape was detected for this period. The steepness and shape of the spectrum above 100 keV rule out chiexp 2 probability 7 x 10exp 4 simple pair cascade models in a compact source which have been suggested for Seyfert galaxies.
- Nuclear Physics and Elementary Particle Physics