Mass-scaling as a method to constrain outflows and particle acceleration from low-luminosity accreting black holes

TL;DR

This paper models the broadband spectra of low-luminosity black holes using mass-scaled outflow models, exploring different jet states and proposing observational tests to distinguish them, thereby advancing understanding of black hole accretion physics.

Contribution

It introduces a mass-scaling approach to model outflows in low-luminosity black holes, comparing two jet scenarios and suggesting observational methods to differentiate them.

Findings

Both A0620-00 and Sgr A* can be modeled with mass-scaled outflow models.

Two outflow scenarios fit the data: synchrotron-self-Compton and synchrotron-dominated states.

Future observations could discriminate between the models through timing of emission in different bands.

Abstract

The `fundamental plane of black hole accretion' (FP), a relation between the radio luminosities ($L_R$), X-ray luminosities ($L_X$), and masses ($M_{BH}$) of hard/quiescent state black hole binaries and low-luminosity active galactic nuclei, suggests some aspects of black hole accretion may be scale invariant. However, key questions still exist concerning the relationship between the inflow/outflow behaviour in the `classic' hard state and quiescence, which may impact this scaling. We show that the broadband spectra of A0620-00 and~\sgra~(the least luminous stellar mass/supermassive black holes on the FP) can be modelled simultaneously with a physically-motivated outflow-dominated model where the jet power and all distances are scaled by the black hole mass. We find we can explain the data of both A0620-00 and~\sgra~(in its non-thermal flaring state) in the context of two outflow-model scenarios: (1) a synchrotron-self-Compton dominated state in which the jet plasma reaches highly sub-equipartition conditions (for the magnetic field with respect to that of the radiating particles), and (2) a synchrotron dominated state in the fast-cooling regime in which particle acceleration occurs within the inner few gravitational radii of the black hole and plasma is close to equipartition. We show that it may be possible to further discriminate between models (1) and (2) through future monitoring of its submm/IR/X-ray emission, in particular via time lags between the variable emission in these bands.