Radiatively Inefficient Accretion: Breezes, Winds and Hyperaccretion

TL;DR

This paper reformulates the ADIOS model for radiatively inefficient accretion flows, analyzing adiabatic and radiative cases, and explores the conditions under which winds or breezes occur, including hypercritical accretion scenarios.

Contribution

It introduces a two-zone ADIOS model with equal treatment of inflow and outflow, and examines the effects of radiative losses and hyperaccretion on flow dynamics.

Findings

Mass flux scales as R^1 in adiabatic flows.

Powerful winds and breezes are possible in non-radiative models.

Radiative losses lead to a power-law behavior with n<1.

Abstract

We reformulate the adiabatic inflow-outflow (ADIOS) model for radiatively inefficient accretion flows, treating the inflow and outflow zones on an equal footing. For purely adiabatic flows (i.e., with no radiative losses), we show that the mass flux in each zone must satisfy Mdot ~ R^n with n=1, in contrast to previous work in which 0<n< 1 is a free parameter but in rough agreement with numerical simulations. We also demonstrate that the resulting two-zone ADIOS models are not dynamically self-consistent without the introduction of an energy source close in to the central regions of the flow; we identify this with the energy liberated by accretion. We explore the parameter space of non-radiative models and show that both powerful winds and gentle breezes are possible. When small radiative losses (with fixed efficiency) are included, any centrally injected energy flux is radiated away and the system reverts to a power-law behavior with n < 1, where n falls in a small range determined by the fractional level of radiative losses. We also present an ADIOS model for hypercritical (super-Eddington) disk accretion, in which the radiative losses are closely related to the flow geometry. We suggest that hyperaccretion can lead to either winds or breezes.