arXiv subjects
Publications and source records attributed to Wolfgang J. Duschl.
We demonstrate that the accretion disk model for the Galactic Center region by Linden et al (1993a) is applicable for at least one order of magnitude in radius from the Galactic Center (10 ... 100 pc). The viscosity $ν$ is shown to be weakly dependent on the radius $s$: $ν\sim s^{0.4}$. Finally, we discuss the influence of the inner boundary on the structure of the inner disk regions.
Recent observations of Sgr A* give strong constraints for possible models of the physical nature of Sgr A* and suggest the presence of a massive black~hole with M<2 10^6 M_sun surrounded by an accretion disk which we estimate to radiate at a luminosity of <7 10^5 L_sun. We therefore calculate the appearance of a standard accretion disk around a Kerr hole in Sgr A* following from general relativity and a few fundamental assumptions. Effective temperature and luminosity of the disk spectra do not depend on the unknown viscosity mechanism but instead are quite sensitive to variations of intrinsic parameters: the mass, the accretion rate, the angular momentum of the accreting hole and the inclination angle. A radiation field of L~7 10^4 - 7 10^5 L_sun and T_eff ~ 2-4 10^4 K can be ascribed to a rapidly rotating Kerr~hole (a>0.9) accreting 10^-8.5 - 10^-7 M_sun/yr at a black~hole mass of M=2 10^6 M_sunseen almost edge on. A low mass black hole of M<10^3 M_sun seems to be very unlikely. We provide a ``Hertzsprung-Russell diagram for black holes'' together with simple scaling laws to provide an easy-to-handle test for the black hole model.