Thermally Driven Winds from Radiatively Inefficient Accretion Flows

TL;DR

This paper investigates thermally driven winds from radiatively inefficient accretion flows (RIAFs), revealing that wind outflow rates are comparable to accretion rates and highlighting the impact of wind cooling on the accretion flow's energy spectrum.

Contribution

It provides a self-similar model for the vertical structure of winds in RIAFs and quantifies the mass loss rate, offering new insights into the dynamics of low-luminosity accretion flows.

Findings

Wind outflow rate is roughly equal to accretion rate for alpha ≤ 0.1.

Accretion rate in RIAFs is approximately proportional to radius.

Wind cooling significantly affects the energy spectrum of RIAFs.

Abstract

Radiatively inefficient accretion flows (RIAFs) are common feature of low-luminosity accretion flows, including quiescent states of X-ray binaries and low-lunimosity active galactic nuclei. Thermally driven winds are expected from such hot accretion flows. By assuming that the flow has self-similarity structure in the radial direction, we solve the vertical structure of the wind and accretion flows simultaneously and evaluate the mass loss rates by wind. We find that the ratio of the outflow rate to the accretion rate is approximately unity for a viscosity parameter, alpha lesssim 0.1, despite some uncertainties in the angular momentum and temperature distributions. That is, the accretion rate in the RIAFs is roughly proportional to the radius. Moreover, we elucidate the effect of cooling by wind on the underneath accretion flow, finding that this effect could be important for calculating energy spectrum of the RIAF. Observational implications are briefly discussed in the context of Sgr A*.