THE NONTHERMAL PAIR MODEL FOR THE X-RAY AND GAMMA-RAY SPECTRA FROM ACTIVE GALACTIC NUCLEI

The nonthermal pair model for the X- and gamma-ray spectra from Seyfert 1 type galaxies disagreed with the few data available at the introduction of the model 1983-1985. Presently, this few-parameter model (with a few enhancements) is the only model that (1) includes most of the relevant microphysics, (2) that can explain most of the general features of the EUV-gamma-ray spectra of Seyfert 1 galaxies, and (3) that at the same time can fit nonstandard spectra of individual objects (such as NGC 4151). Successful fits for NGC 4151 require that the released power is channelled to both thermal and nonthermal particles. An important test of the model will be the detailed time-dependent shape of the hard X-ray spectral breaks that future missions, such as INTEGRAL, will provide.