Thermal conduction in accretion disk coronae

Abstract

We study the effects of thermal conduction in a hot, active corona above an accretion disk. We assume that all of the dissipative heating takes place in the corona. We find that the importance of conduction decreases with increases in the local dissipative compactness of the corona, l_{diss,loc}, and increases with increasing abundance of electron-positron pairs. For l_{diss,loc} < 1, a significant fraction of the energy released in the corona may be carried away by the conductive flux, leading to formation of a relatively hot transition layer below the base of the corona. Comptonization of disk radiation in such a layer may account for the presence of soft X-ray excesses in the spectra emitted by disk-corona systems.