Particle acceleration close to the supermassive black hole horizon: the case of M87

TL;DR

This paper proposes a novel pulsar-like model for explaining the rapid TeV gamma-ray variability observed near the supermassive black hole in M87, involving magneto-centrifugal electron acceleration and inverse Compton scattering.

Contribution

It introduces a new pulsar-type scenario for VHE emission near black holes, challenging conventional models and linking VHE observations to inner accretion disk conditions.

Findings

Magneto-centrifugal electrons can upscatter sub-mm photons to TeV energies.

The model explains rapid TeV variability in M87.

VHE observations can probe inner accretion disk environments.

Abstract

The radio galaxy M87 has recently been found to be a rapidly variable TeV emitting source. We analyze the implications of the observed TeV characteristics and show that it proves challenging to account for them within conventional acceleration and emission models. We discuss a new pulsar-type scenario for the origin of variable, very high energy (VHE) emission close to the central supermassive black hole and show that magneto-centrifugally accelerated electrons could efficiently Compton upscatter sub-mm ADAF disk photons to the TeV regime, leading to VHE characteristics close to the observed ones. This suggests, conversely, that VHE observations of highly under-luminous AGNs could provide an important diagnostic tool for probing the conditions prevalent in the inner accretion disk of these sources.