Black hole lightning due to particle acceleration at subhorizon scales

TL;DR

This paper reports rapid gamma-ray variability in the radio galaxy IC 310, suggesting particle acceleration near the black hole's magnetosphere as the source of intense, fast-changing emission.

Contribution

It introduces evidence of subhorizon scale emission regions in a supermassive black hole, linking gamma-ray variability to magnetospheric particle acceleration.

Findings

Gamma-ray doubling times less than 4.8 minutes.

Emission region smaller than 20% of the black hole's gravitational radius.

Evidence for pulsar-like particle acceleration mechanisms.

Abstract

Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry, but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here, we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC telescopes revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20\% of the gravitational radius of its central black hole. We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet.