Truncated disks - advective tori solutions around BHs. I. The effects of conduction and enhanced Coulomb coupling

Details Truncated disks - advective tori solutions around BHs. I. The effects of conduction and enhanced Coulomb coupling Truncated disks - advective tori solutions around BHs. I. The effects of conduction and enhanced Coulomb coupling

Oct 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26a...362l..41h&link_type=abstract

Astronomy and Astrophysics, v.362, p.L41-L44 (2000)

Physics

9

Magnetic Fields, Magnetohydrodynamics (Mhd), Accretion, Accretion Disks, Black Hole Physics, Hydrodynamics, Methods: Numerical

Scientific paper

We present the first 2D quasi-stationary radiative hydrodynamical calculations of accretion flows onto BHs taking into account cooling via Bremsstrahlung, Compton, Synchrotron and conduction. The effect of enhanced Coulomb coupling is investigated also. Based on the numerical results obtained, we find that two-temperature (2T) accretion flows are best suited to describe hard states, and one-temperature (1T) in the soft states, with transition possibly depending on the accretion rate. In the 2T case, the ion-conduction enlarges the disk-truncation-radius from 5 to 9 Schwarzschild radii (RS). The ion-pressure powers outflows, hence substantially decreasing the accretion rate with decreasing radius. The spectrum is partially modified BB with hard photons emitted from the inner region and showing a cutoff at 100 keV. In the 1T case, conduction decreases the truncation radius from 7 to 5 RS and lowers the maximum gas temperature. The outflows are weaker, the spectrum is pre-dominantly modified BB and the emitted photons from the inner region are much harder (up to 175 keV). In both cases, the unsaturated Comptonization region coincides with the transition region between the disk and the advective torus. When gradually enhancing the Coulomb coupling, we find that the ion-temperature Ti decreases and the electron temperature Te increases, asymptotically converging to 1T flows. However, once the dissipated energy goes into heating the ions, ion-electron thermal decoupling is inevitable within the last stable orbit (RMS) even when the Coulomb interaction is enhanced by an additional two orders of magnitude.

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