W. N. Johnson

OSSE observations of the bright Seyfert 1 galaxy IC 4329A

We present the first hard X-ray/soft γ-ray observations from the Oriented Scintillation Spectrometer Experiment (OSSE) of a bright Seyfert 1 galaxy, IC 4329A. Significant variability was seen over the 3 week observing period. The 50-200 keV spectrum is steep and can be characterized by a power-law spectrum of photon index 2.84±0.36, at 90% confidence. This is significantly steeper than the X-ray spectrum found from Ginga data of the source. Joint fits of the Ginga and OSSE data are well modeled by a thermal model represented by an exponential spectral break with an e-folding energy at about 130 keV. Good fits are also obtained if a reflection component is included. We constrain possible nonthermal continuum models involving photon-photon pair production