Warm and thick corona for magnetically supported disk in GBHB

This paper is devoted to self-consistent modeling of the magnetically supported accretion disk with optically thick warm corona based on first principles. In our model, we consider the gas heating by magneto-rotational instability (MRI) dynamo. Our goal is to show that the proper calculation of the gas heating by magnetic dynamo can build up the warm, optically thick corona above the accretion disk around black hole of stellar mass. Using vertical model of the disk supported and heated by the magnetic field together with radiative transfer in hydrostatic and radiative equilibrium we developed relaxation numerical scheme which allows us to compute the transition form the disk to corona in a self consistent way. We demonstrate here that the warm (up to 5 keV), optically thick (up to 10 Thompson optical depths), Compton cooled corona can form due to the magnetic heating. Such warm corona is stronger for higher accretion rate and larger magnetic field strength. The radial extent of the warm corona is limited by the occurrence of the local thermal instability, which purely depends on radiative processes. The obtained coronal parameters are in agreement with those constrained from X-ray observations. The warm magnetically supported corona is tends to appear in the inner disk regions. It may be responsible for Soft X-ray excess seen in accreting sources. For lower accretion rates and weaker magnetic field parameters, thermal instability prevents warm corona to exist, giving rise to eventual clumpiness or ionized outflow.
Comment: accepted for publication in A&A on 4 Sep 2019