Warm and thick corona for a magnetically supported disk in galactic black hole binaries

Abstract

Context. 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. Aims. 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.Methods. 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. Results. We demonstrate here that the warm (up to 5 keV), optically thick (up to 10 τ es ), 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. Conclusions. 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.

An extreme ultraluminous X-ray source X-1 in NGC 5055

“…The temperature of the corona from the MCD+NTHCOMP best-fit model is quite low kT e ∼ 1.68−1.78 keV. This is commonly observed in ULXs (Gladstone et al 2009) and can be ascribed to a cool corona, reminiscent of the soft X-ray excess often observed in some BH accreting sources (Gronkiewicz & Różańska 2020;Petrucci et al 2020, and references therein).…”

Possible mechanism for multiple changing-look phenomena in active galactic nuclei

“…It also implies that for lower Eddington ratio objects the instability would not operate, while for higher Eddington ratio objects this mechanism would lead to outbursts of a much larger part of the disk and it would operate on a timescale of thousands of years, as typically predicted for the radiation pressure instability (Janiuk et al 2002;Czerny et al 2009;Wu et al 2016;Grze ¸dzielski et al 2017). However, if the evolution includes the time-dependent coronal flow (e.g., Janiuk & Czerny 2007) or time-dependent vertical stratification of the disk into cold standard disk and the warm corona (e.g., Czerny et al 2003b;Gronkiewicz & Różańska 2020;Petrucci et al 2020), the timescales will be strongly affected by quadratic dependence of the viscous timescale on the ratio of the local medium geometrical thickness to the local radius.…”

The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy

“…However, through recent radiative transfer computation in hydrostatic and radiative equilibrium, Gronkiewicz & Różańska (2020) has shown that for lower accretion rates, thermal instability should prevent the warm corona from forming. The low accretion rate system is unable to provide enough energy to sustain a warm corona (Ballantyne & Xiang 2020).…”