Spectral Models of Advection‐dominated Accretion Flows with Winds

Abstract

We calculate spectral models of advection-dominated accretion flows, taking into account the possibility that significant mass may be lost to an outflow/wind. We apply the models to the soft X-ray transient V404 Cyg in quiescence, the Galactic center source Sgr A*, and the nucleus of NGC 4649. We show that there are qualitative degeneracies between the mass-loss rate in the wind and parameters characterizing the microphysics of the accretion flow; of particular importance is δ, the fraction of the turbulent energy which heats the electrons. For small δ, current observations suggest that at most 90% of the mass originating at large radii is lost to a wind, so that at least ~10% reaches the central object. For large δ ~ 0.3, however, models with significantly more mass loss are in agreement with the observations. We conclude by highlighting future observations which may clarify the importance of mass loss in sub-Eddington accretion flows.