Repeated pattern of gamma-ray flares in the lightcurve of the blazar 3C 279

TL;DR

This study identifies repeating gamma-ray flare patterns in the blazar 3C 279's lightcurve that are associated with optical polarization rotations, supporting models of jet emission features propagating within the blazar.

Contribution

It reveals a complex, repeating gamma-ray flare pattern linked to polarization rotations, including a hidden event, supporting jet emission models in blazars.

Findings

Repeated gamma-ray flare patterns are associated with polarization rotations.

A hidden EVPA rotation was detected in the relative Stokes parameters.

Findings support jet emission feature propagation models.

Abstract

The optical polarization plane of some blazars occasionally exhibits smooth hundred degree long rotations. Multiple theoretical models have been proposed to explain the nature of such events. A deterministic origin of these rotations, however, remains uncertain. We aim to find repeating patterns of flares in gamma-ray light curves of blazars, which accompany optical polarization plane rotations. Such patterns have been predicted to occur by one of the models explaining this phenomenon. For the blazar 3C 279, where multiple polarization plane rotations have been reported in the literature, we obtain the Fermi-LAT gamma-ray light curve and analyze its intervals adjacent to polarization plane rotations. We find a complex characteristic pattern of flares in the gamma-ray light curve that is repeated during periods adjacent to three large amplitude EVPA rotation events in 3C 279. We discover a "hidden EVPA rotation", which can only be seen in the relative Stokes parameters plane and that occurred simultaneously with the fourth repetition of the pattern. This finding strongly favors the hypothesis of emission features propagating in the jet as the reason of optical polarization plane rotations. Furthermore, it is compatible with the hypothesis of a sheath in the jet comprised of more slowly propagating emission features.