SPHERICALLY SYMMETRIC NEAR-CRITICAL ACCRETION ONTO NEUTRON-STARS

Numerical and approximate analytic solutions for time-independent, spherically symmetric, radiation pressure-dominated accretion flows are presented. For flows with luminosities at infinity L(∞) sufficiently close to the Eddington limit Lcrit, the flow velocity profile is qualitatively different from the modified free-fall profile υ(r) = [1 - L(∞)/Lcrit,]1/2(2GM/r)1/2. Advective contributions to the comoving radiation flux decelerate the flow within a critical radius, and in this settling region the velocity of the flow decreases linearly with decreasing radius.