A Tight Connection Between Gamma-Ray Outbursts and Parsec-Scale Jet Activity in the Quasar 3c 454.3

Abstract

We analyze the multi-frequency behavior of the quasar 3C 454.3 during three prominent γ -ray outbursts: 2009 Autumn, 2010 Spring, and 2010 Autumn. The data reveal a repeating pattern, including a triple flare structure, in the properties of each γ -ray outburst, which implies similar mechanism(s) and location for all three events. The multi-frequency behavior indicates that the lower frequency events are co-spatial with the γ -ray outbursts, although the γ -ray emission varies on the shortest timescales. We determine that the variability from UV to IR wavelengths during an outburst results from a single synchrotron component whose properties do not change significantly over the different outbursts. Despite a general increase in the degree of optical linear polarization during an outburst, the polarization drops significantly at the peak of the γ -ray event, which suggests that both shocks and turbulent processes are involved. We detect two disturbances (knots) with superluminal apparent speeds in the parsec-scale jet associated with the outbursts in 2009 Autumn and 2010 Autumn. The kinematic properties of the knots can explain the difference in amplitudes of the γ -ray events, while their millimeterwave polarization is related to the optical polarization during the outbursts. We interpret the multi-frequency behavior within models involving either a system of standing conical shocks or magnetic reconnection events located in the parsec-scale millimeter-wave core of the jet. We argue that γ -ray outbursts with variability timescales as short as ∼3 hr can occur on parsec scales if flares take place in localized regions such as turbulent cells.

Polarization Signatures of Relativistic Magnetohydrodynamic Shocks in the Blazar Emission Region. I. Force-Free Helical Magnetic Fields

“…If the shock/ disturbance is slightly faster, then it is plausible to build up the toroidal component and lead to significant polarization variations such as the PA rotations; but in both cases, the flux will not increase sufficiently to produce a flare. Such polarization variations with no obvious flares are consistent with some observations (e.g., Itoh et al 2013;Jorstad et al 2013). However, Kirk et al (2000) and Achterberg et al (2001) have shown that for relativistic shocks, the hardest obtainable particle power-law index is approximately…”

The central pc-scale region in blazars: insights from multi-band observations

“…The highest levels of the emission Mg II line flux and γ-ray outburst happens when a jet component passes through (or ejected from) the radio core of 3C 454.3. This remarkable event was also confirmed in consequent studies (Isler et al 2013;Jorstad et al 2013).…”

Erratic Flaring of Bl Lac in 2012–2013: Multiwavelength Observations

“…In addition, when knot K11b encountered stationary knot A2, it brightened and became more highly polarized (Figure 19 The higher polarization when superluminal knots K11b and K12b reached stationary knot A2 could have been caused by an increase in the strength and order of the magnetic field from compression by a stationary shock corresponding to A2. This situation bears a striking resemblance to that in 3C 454.3 when new knot K09 encountered stationary knot C (Wehrle et al 2012b;Jorstad et al 2013). Just as in the case of 3C 454.3, the stationary knot's EVPA is always nearly aligned with the jet direction, a signature of a transversely oriented shock with magnetic field compressed along the shock front (Hughes et al 1985(Hughes et al , 1989.…”