Cyclo-synchrotron emission from magnetically dominated active regions above accretion discs

Abstract

We discuss the role of thermal cyclo-synchrotron emission in a magnetically dominated corona above an accretion disk in an active galaxy or a galactic black hole candidate. The dissipation occurs in localized active regions around the central black hole. Cyclo-synchrotron radiation is found to be an important process. In the case of galactic black hole candidates, its emission can dominate the inverse Compton scattering of the soft photon field produced by the disc by thermal electrons. We discuss observational predictions and the detectability of cyclo-synchrotron radiation both for these sources and radio-quiet active galactic nuclei.