Theoretical implications of the recent simultaneous ROSAT/OSSE observation of the Seyfert 1 IC 4329A are discussed. We find that either thermal or non-thermal Comptonization models can fit the data. Thermal models require optically thin plasma and mildly relativistic electrons. Non-thermal models require most of the injected power to be at low values of the electron Lorentz factor. Both models predict a spectral cut-off at energies below ∼ 1 MeV, which agrees with broad-band data including non-simultaneous Ginga spectra that match the ROSAT 2-keV flux. Also, Compton reflection corresponding to cold matter covering a solid angle of 2π is required, and partial covering is ruled out. Since the spectrum of IC 4329A is typical of Seyfert 1s, their contribution to the cosmic hard X-ray background can be estimated: without cosmological evolution, it is 30 per cent at 3 keV. As the peak of the vFv spectrum of IC 4329A is much broader than that of the hard X-ray background, however, Seyfert 1s cannot account for the X-ray background spectrum without spectral evolution.
CITATION STYLE
Zdziarski, A. A., Fabian, A. C., Nandra, K., Celotti, A., Rees, M. J., Done, C., … Madejski, G. M. (1994). Physical processes in the X-ray/gamma-ray source of IC 4329A. Monthly Notices of the Royal Astronomical Society, 269(1), L55–L60. https://doi.org/10.1093/mnras/269.1.l55
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