Two‐Temperature Coronal Flow above a Thin Disk

We extended the disk corona model (Meyer & Meyer-Hofmeister 1994; Meyer, Liu,& Meyer-Hofmeister 2000a) to the inner region of galactic nuclei by includingdifferent temperatures in ions and electrons as well as Compton cooling. Wefound that the mass evaporation rate and hence the fraction of accretion energyreleased in the corona depend strongly on the rate of incoming mass flow fromouter edge of the disk, a larger rate leading to more Compton cooling, lessefficient evaporation and a weaker corona. We also found a strong dependence onthe viscosity, higher viscosity leading to an enhanced mass flow in the coronaand therefore more evaporation of gas from the disk below. If we take accretionrates in units of the Eddington rate our results become independent on the massof the central black hole. The model predicts weaker contributions to the hardX-rays for objects with higher accretion rate like narrow-line Seyfert 1galaxies (NLS1s), in agreement with observations. For luminous active galacticnuclei (AGN) strong Compton cooling in the innermost corona is so efficientthat a large amount of additional heating is required to maintain the coronaabove the thin disk.Comment: 17 pages, 6 figures. ApJ accepte