Preheated Advection‐dominated Accretion Flow

All high temperature accretion solutions including ADAF are physically thick,so outgoing radiation interacts with the incoming flow, sharing as much or moreresemblance with classical spherical accretion flows as with disk flows. Weexamine this interaction for the popular ADAF case. We find that withoutallowance for Compton preheating, a very restricted domain of ADAF solution ispermitted and with Compton preheating included a new high temperature PADAFbranch appears in the solution space. In the absence of preheating, hightemperature flows do not exist when the mass accretion rate mdot == Mdot c^2 /L_E >~ 10^-1.5. Below this mass accretion rate, a roughly conical region aroundthe hole cannot sustain high temperature ions and electrons for all flowshaving mdot >~ 10^-4, which may lead to a funnel possibly filled with a tenuoushot outgoing wind. If the flow starts at large radii with the usual equilibriumtemperature ~10^4 K, the critical mass accretion rate is much lower, mdot\~10^-3.7 above which level no self-consistent ADAF (without preheating) canexist. However, above this critical mass accretion rate, the flow can beself-consistently maintained at high temperature if Compton preheating isconsidered. These solutions constitute a new branch of solutions as inspherical accretion flows. High temperature PADAF flows can exist above thecritical mass accretion rate in addition to the usual cold thin disk solutions.We also find solutions where the flow near the equatorial plane accretesnormally while the flow near the pole is overheated by Compton preheating,possibly becoming, a polar wind, solutions which we designate WADAF.Comment: 41 pages with 10 postscript figures (aastex5). Submitted to Ap