RoboPol: optical polarization-plane rotations and flaring activity in blazars

Blinov, D.; Pavlidou, V.; Papadakis, I. E.; Hovatta, T.; Pearson, T. J.; Liodakis, Ioannis; Panopoulou, G. V.; Angelakis, E.; Baloković, Mislav; Das, H. K.; Khodade, P.; Kiehlmann, S.; King, O. G.; Kus, A. J.; Kylafis, N. D.; Mahabal, A.; Marecki, A.; Modi, Deepa; Myserlis, I.; Paleologou, E. V.; Papamastorakis, I.; Pazderska, B.; Pazderski, E.; Rajarshi, C.; Ramaprakash, A. N.; Readhead, A. C. S.; Reig, P.; Tassis, Konstantinos; Zensus, J. A.

doi:10.1093/mnras/stw158

Cited by 80 publications

(117 citation statements)

References 33 publications

(36 reference statements)

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“…During the first observing season of RoboPol in 2013, we detected a 128 degree EVPA rotation in the HSP source PG 1553+113 (Blinov et al 2015). The same source was seen to rotate during 2014 as well by about 145 degrees, as reported in Blinov et al (2016), confirming the TeV HSPs as a class of objects with EVPA rotations (see also Jermak et al 2016).…”

Section: Rotations In the Polarization Planesupporting

confidence: 70%

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Optical polarization of high-energy BL Lacertae objects

Hovatta

Lindfors

Blinov

et al. 2016

A&A

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Context. We investigate the optical polarization properties of high-energy BL Lac objects using data from the RoboPol blazar monitoring program and the Nordic Optical Telescope. Aims. We wish to understand if there are differences in the BL Lac objects that are detected with the current-generation TeV instruments compared to those that have not yet been detected. Methods. We use a maximum likelihood method to investigate the optical polarization fraction and its variability in these sources. In order to study the polarization position angle variability, we calculate the time derivative of the electric vector position angle (EVPA) change. We also study the spread in the Stokes Q/I − U/I-plane and rotations in the polarization plane. Results. The mean polarization fraction of the TeV-detected BL Lacs is 5% while the non-TeV sources show a higher mean polarization fraction of 7%. This difference in polarization fraction disappears when the dilution by the unpolarized light of the host galaxy is accounted for. The TeV sources show somewhat lower fractional polarization variability amplitudes than the non-TeV sources. Also the fraction of sources with a smaller spread in the Q/I − U/I-plane and a clumped distribution of points away from the origin, possibly indicating a preferred polarization angle, is larger in the TeV than in the non-TeV sources. These differences between TeV and non-TeV samples seems to arise from differences between intermediate and high spectral peaking sources instead of the TeV detection. When the EVPA variations are studied, the rate of EVPA change is similar in both samples. We detect significant EVPA rotations in both TeV and non-TeV sources, showing that rotations can occur in high spectral peaking BL Lac objects when the monitoring cadence is dense enough. Our simulations show that we cannot exclude a random walk origin for these rotations. Conclusions. These results indicate that there are no intrinsic differences in the polarization properties of the TeV-detected and nonTeV-detected high-energy BL Lac objects. This suggests that the polarization properties are not directly related to the TeV-detection, but instead the TeV loudness is connected to the general flaring activity, redshift, and the synchrotron peak location.

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Section: Rotations In the Polarization Planesupporting

confidence: 70%

“…These are shown as shaded regions over the EVPA curves in Appendix A. The rotations in PG 1553+113, GB6 J1037+5711, and S5 2023+760 were already reported in Blinov et al (2016). This shows that EVPA rotations can occur also in ISP and HSP sources if they are observed at high enough cadence.…”

Section: Rotations In the Polarization Planementioning

confidence: 56%

Optical polarization of high-energy BL Lacertae objects

Hovatta

Lindfors

Blinov

et al. 2016

A&A

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“…All of these cases of definite rotations occurred during or close to major optical and/or γ-ray outbursts and to ejections of new superluminal VLBI jet components. Numerous cases of rotations are also reported in [9,10].…”

Section: Rotations: Realmentioning

confidence: 95%

“…Blinov et al in [10], based on the two-year observational data set of the ROBOPOL project, arrive at several important conclusions. Particularly: (1) there is no statistical association of the rotations with contemporaneous optical flares; (2) the average PD during the rotations tends to be lower than that in a non-rotating state.…”

Section: Introductionmentioning

confidence: 99%

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Polarization Vector Rotations: Real, Spurious, Hidden and Imaginary

Larionov¹,

Jorstad

Marscher

et al. 2016

Galaxies

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Large and variable polarization is an inherent property of a majority of blazars. Systematic rotations of the polarization vector have been claimed for several blazars. In some cases, however, the reality of these rotations may be questionable. We suggest an additional method for the verification of the reality of polarization position angle rotations based on the correlation of the normalized Stokes parameters.

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Relativistic Jets in Active Galactic Nuclei and Microquasars

Romero¹,

Boettcher²,

Markoff³

et al. 2017

Jets and Winds in Pulsar Wind Nebulae, Gamma-Ray Bursts and Blazars

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Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly understood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravitational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by γ-ray emission observed from many jet sources) and the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially

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RoboPol: optical polarization-plane rotations and flaring activity in blazars

Cited by 80 publications

References 33 publications

Optical polarization of high-energy BL Lacertae objects

Optical polarization of high-energy BL Lacertae objects

Polarization Vector Rotations: Real, Spurious, Hidden and Imaginary

Relativistic Jets in Active Galactic Nuclei and Microquasars

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