Polarization swings in blazars

Lyutikov, Maxim; Kravchenko, Evgeniya V.

doi:10.1093/mnras/stx359

Cited by 35 publications

(33 citation statements)

References 55 publications

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“…However, we cannot discard the possibility that the polarized emission of this epoch is still associated with the core, which is also in a renewed high state of flux. A rotation of 90 • is expected because of opacity effects (Pacholczyk 1970) or even because of changes of the jet orientation with respect to our line of sight (Lyutikov & Kravchenko 2017). In both cases, however, a strong decrease of the degree of polarization is expected.…”

Section: The Polarized Emission Evolution At 43 Ghzmentioning

confidence: 86%

The magnetic field structure in CTA 102 from high-resolution mm-VLBI observations during the flaring state in 2016–2017

Casadio

Marscher

Jorstad

et al. 2019

A&A

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Context. Investigating the magnetic field structure in the innermost regions of relativistic jets is fundamental to understanding the crucial physical processes giving rise to jet formation, as well as to their extraordinary radiation output up to γ-ray energies. Aims. We study the magnetic field structure of the quasar CTA 102 with 3 and 7 mm VLBI polarimetric observations, reaching an unprecedented resolution (∼50 µas). We also investigate the variability and physical processes occurring in the source during the observing period, which coincides with a very active state of the source over the entire electromagnetic spectrum. Methods. We perform the Faraday rotation analysis using 3 and 7 mm data and we compare the obtained rotation measure (RM) map with the polarization evolution in 7 mm VLBA images. We study the kinematics and variability at 7 mm and infer the physical parameters associated with variability. From the analysis of γ-ray and X-ray data, we compute a minimum Doppler factor value required to explain the observed high-energy emission.Results. Faraday rotation analysis shows a gradient in RM with a maximum value of ∼6×10 4 rad/m 2 and intrinsic electric vector position angles (EVPAs) oriented around the centroid of the core, suggesting the presence of large-scale helical magnetic fields. Such a magnetic field structure is also visible in 7 mm images when a new superluminal component is crossing the core region. The 7 mm EVPA orientation is different when the component is exiting the core or crossing a stationary feature at ∼0.1 mas. The interaction between the superluminal component and a recollimation shock at ∼0.1 mas could have triggered the multi-wavelength flares. The variability Doppler factor associated with such an interaction is large enough to explain the high-energy emission and the remarkable optical flare occurred very close in time.

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Section: The Polarized Emission Evolution At 43 Ghzmentioning

confidence: 86%

The magnetic field structure in CTA 102 from high-resolution mm-VLBI observations during the flaring state in 2016–2017

Casadio

Marscher

Jorstad

et al. 2019

A&A

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“…Blinov et al 2018). The picture appears quite complex, as changes in the jet viewing angle can mimic a stochastic process even when the variations in flux and P , and EVPA rotations, are produced by a deterministic process (Lyutikov & Kravchenko 2017).…”

Section: Polarimetric Observationsmentioning

confidence: 99%

The beamed jet and quasar core of the distant blazar 4C 71.07

Raiteri

Villata

Carnerero

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The object 4C 71.07 is a high-redshift blazar whose spectral energy distribution shows a prominent big blue bump and a strong Compton dominance. We present the results of a two-year multiwavelength campaign led by the Whole Earth Blazar Telescope (WEBT) to study both the quasar core and the beamed jet of this source. The WEBT data are complemented by ultraviolet and X-ray data from Swift, and by γ-ray data by Fermi. The big blue bump is modelled by using optical and near-infrared mean spectra obtained during the campaign, together with optical and ultraviolet quasar templates. We give prescriptions to correct the source photometry in the various bands for the thermal contribution, in order to derive the non-thermal jet flux. The role of the intergalactic medium absorption is analysed in both the ultraviolet and X-ray bands. We provide opacity values to deabsorb ultraviolet data, and derive a best-guess value for the hydrogen column density of N best H = 6.3 × 10 20 cm −2 through the analysis of Xray spectra. We estimate the disc and jet bolometric luminosities, accretion rate, and black hole mass. Light curves do not show persistent correlations among flux changes at different frequencies. We study the polarimetric behaviour and find no correlation between polarisation degree and flux, even when correcting for the dilution effect of the big blue bump. Similarly, wide rotations of the electric vector polarisation angle do not seem to be connected with the source activity.

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“…These rotations are sometimes associated with flares in total intensity and drops in Π (Blinov et al 2016). Various models have been proposed to explain this behavior, including a turbulent stochastic model (Marscher 2014), a spiraling jet (Lyutikov & Kravchenko 2017) and a helical kink propagating along a conical jet (Nalewajko 2017). Although these pictures can accommodate multicycle rotations, they fail to address the optical trends found in Blinov et al (2016).…”

Section: Introductionmentioning

confidence: 99%

The Polarization Behavior of Relativistic Synchrotron Self-Compton Jets

Peirson

Romani

2019

ApJ

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We describe a geometric model for synchrotron and synchrotron self-Compton (SSC) radiation from blazar jets, involving multiple emission zones with turbulent magnetic fields and fully self-consistent seed photon mixing for SSC. Including the effects of jet divergence, particle cooling and the Relativistic PA rotation (RPAR) to the observer frame, we find that the multi-zone model recovers simple predictions for SSC polarization, but describes new dependencies on jet viewing geometry and zone multiplicity. Increasing the zone number decreases both synchrotron and SSC polarization, but with different scaling. A rise in synchrotron polarization fraction Π Sync at high energies is guaranteed by basic relativity considerations, and strengthened by jet non-uniformity. Finite light travel time effects can suppress the synchrotron polarization at energies well below the ν Sync peak. In general Π Sync and Π SSC are correlated with Π SSC /Π Sync ≈ 0.3, but individual realizations can lie far from this trend. This study lets us estimate Π across the SED, leading to predictions in the X-ray band helpful for planning observations with IXPE and other upcoming X-ray polarization missions.

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Polarization swings in blazars

Cited by 35 publications

References 55 publications

The magnetic field structure in CTA 102 from high-resolution mm-VLBI observations during the flaring state in 2016–2017

The magnetic field structure in CTA 102 from high-resolution mm-VLBI observations during the flaring state in 2016–2017

The beamed jet and quasar core of the distant blazar 4C 71.07

The Polarization Behavior of Relativistic Synchrotron Self-Compton Jets

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