Flaring Active Galactic Nuclei. The cases of 3C 279 and PMN J0948+0022 as seen by the Fermi-LAT

TL;DR

This paper analyzes gamma-ray flares from active galactic nuclei, specifically 3C 279 and PMN J0948+0022, using Fermi-LAT data, revealing correlations with optical polarization changes and identifying a first flare in a narrow-line Seyfert 1 galaxy.

Contribution

It presents detailed gamma-ray observations of two different flaring AGNs, highlighting the first detection of a flare in a narrow-line Seyfert 1 galaxy and the correlation with optical polarization.

Findings

Gamma-ray flare from 3C 279 coincides with optical polarization change.

First gamma-ray flare detected from PMN J0948+0022.

Multiwavelength campaigns provide insights into AGN flaring behavior.

Abstract

Active galactic nuclei (AGNs) exhibit variability across the entire electromagnetic spectrum with distinct flaring episodes at different frequencies. The high sensitivity and nearly uniform sky coverage of the Large Area Telescope on board the Fermi satellite make it a powerful tool for monitoring a large number of AGNs over long timescales. This allowed us to detect several flaring AGNs in gamma rays, triggering dedicated multifrequency campaigns on these sources from radio to TeV energies. We discuss the results for two different types of flaring AGN: the flat spectrum radio quasar 3C 279, in particular the coincidence of a gamma-ray flare from this source with the drastic change of the optical polarization angle, and the first gamma-ray flare from a radio-loud narrow-line Seyfert 1, PMN J0948+0022.