2004/06/25 by Jun Fukue, Jun Fükue · 6 citations
Physics and Astronomy · Earth and Planetary Sciences · #Astrophysical Phenomena and Observations #High-pressure geophysics and materials #Astrophysics and Star Formation Studies
paper · pdf · doi:10.1093/pasj/56.3.569
For a supercritical accretion regime, we propose a critical accretion disk, where the mass-accretion rate is regulated just at the critical rate with the help of wind mass-loss. We first derive a critical radius, inside of which the standard picture is violated, using the condition that the radiative force is balanced by the gravity in the vertical direction. The critical radius rcr is found to be rcr = (9√(3)σT / 16π c mp) Minput = 1.95 (Minput / Mcrit) rg, where Minput is the mass-accretion rate at the outer edge of the disk, Mcrit the critical accretion rate, and rg the Schwarzschild radius of the central object. Outside of this critical radius, the disk is in a radiation-pressure dominated standard state, while inside this radius the disk is in a critical state, where the excess mass is expelled by wind and the accretion rate is kept to be just at the critical rate at any radius inside rcr. In such a critical accretion disk, the disk thickness is H ∼ (1/6√(3))r and the surface temperature is σ T4 ∼ (2/3√(3)) LE / 4π r2, where LE is the Eddington luminosity. The total disk luminosity becomes Ldisk ∼ (2/3√(3)) [ln (rcr/rin)+1] LE, where rin is the inner radius. We apply the present model to microquasars and narrow-line Seyfert 1 galaxies, which are supposed to be under supercritical accretion.