A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279

TL;DR

This study reports a gamma-ray flare in blazar 3C 279 coinciding with a significant change in optical polarization, revealing insights into the jet's magnetic field and emission region location.

Contribution

It provides evidence for co-spatial optical and gamma-ray emission regions and suggests a curved jet trajectory with a distant dissipation zone.

Findings

Optical polarization angle changed dramatically during gamma-ray flare

Emission region is located about 10^5 gravitational radii from the black hole

Jet magnetic field is highly ordered during the event

Abstract

It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. The size of the emitting zone and the location of this region relative to the central supermassive black hole are, however, poorly known, with estimates ranging from light-hours to a light-year or more. Here we report the coincidence of a gamma-ray flare with a dramatic change of optical polarization angle. This provides evidence for co-spatiality of optical and gamma-ray emission regions and indicates a highly ordered jet magnetic field. The results also require a non-axisymmetric structure of the emission zone, implying a curved trajectory for the emitting material within the jet, with the dissipation region located at a considerable distance from the black hole, at about 10^5 gravitational radii.