caa a22 4500 469076984 CHVBK 20180323132937.0 cr unu---uuuuu 170328e19920901xx s 000 0 eng 10.1007/BF02507859 doi (NATIONALLICENCE)springer-10.1007/BF02507859 Ghisellini G. Osservatorio di Torino, 10025, Pino Torinese, Italia aut The origin of the continuum of Active Galactic Nuclei [Elektronische Daten] [G. Ghisellini] Summary: The high-energy continuum of active galactic nuclei can be interpreted by nonthermal models in which electron-positron pairs play a crucial role. The produced primary γ-rays interact with softer photons in the inner, high photon density regions of the source. The created pairs are relativistic, and contribute to the emission, especially in the X-ray band. When the photon density is large enough, therefore for large values of the luminosity-to size ratio, the spectrum produced by the reprocessing due to pairs is predicted to have a characteristic spectral index of one. This power law continuum partly impinges on cold matter, possibly in an accretion disk. The resulting Compton reflected radiation contributes to the X-ray emission, and the predicted overall spectrum is in agreement with the observed shape of the high-energy continuum. The proposed model is easily testable: observations in the hard—X-ray band above (30÷50) keV are crucial to discriminate these nonthermal models against thermal ones. Società Italiana di Fisica, 1992 X-ray sources nationallicence γ-ray sources nationallicence Active nuclei nationallicence Radiaiton mechanisms nationallicence Il Nuovo Cimento C Kluwer Academic Publishers 15/5(1992-09-01), 839-849 0390-5551 15:5<839 1992 15 11543 https://doi.org/10.1007/BF02507859 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02507859 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Ghisellini G. Osservatorio di Torino, 10025, Pino Torinese, Italia aut NATIONALLICENCE 773 0- Il Nuovo Cimento C Kluwer Academic Publishers 15/5(1992-09-01), 839-849 0390-5551 15:5<839 1992 15 11543 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer