X-Ray emission from two-phase accretion disks

Summary We consider a ?two phase? accretion disk consisting of an optically thick layer with temperatureT≃10⁴ K embedded in a hot thin corona (T≃10⁹ K). The main energy input occurs through magnetic heating of the electrons in the corona, while cooling is due to Compton losses of the hot electrons on the soft photons provided by the thick layer. We write the balance equations for the two phases. We show that a possible mode of variability yields steeper spectra for increasing soft-photon luminosity as observed in Seyfert galaxies and compute composite model spectra in the X-ray range, via Monte Carlo simulations. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.