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 vF_v_ 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.
Physical processes in the X-ray/gamma-ray source of IC 4329A / Zdziarski, A. A.; Fabian, A. C.; Nandra, K.; Celotti, Anna Lisa; Rees, M. J.; Done, C.; Coppi, P. S.; Madejski, G. M.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 269:4(1994), pp. L55-L60. [10.1093/mnras/269.1.L55]
Physical processes in the X-ray/gamma-ray source of IC 4329A
Celotti, Anna Lisa;
1994-01-01
Abstract
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 vF_v_ 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.