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Galaxies 2016, 4(4), 72; doi:10.3390/galaxies4040072

Multi-Frequency Monitoring of the Flat Spectrum Radio Quasar PKS 1222+216 in 2008–2015

1
Astronomical Institute, St. Petersburg State University, Universitetsky Prospekt, 28, Peterhof, St. Petersburg 198504, Russia
2
Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
3
Instituto de Astrofisíca de Andalucía, CSIC, Glorieta de la Astronomía, Granada E-18008, Spain
4
Department of Physics, Institute for Plasma Physics, University of Crete, Heraklion GR-71003, Greece
5
Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Emilio Elizalde
Received: 15 July 2016 / Revised: 20 November 2016 / Accepted: 21 November 2016 / Published: 28 November 2016
(This article belongs to the Special Issue Blazars through Sharp Multi-wavelength Eyes)
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Abstract

We analyze the broadband activity of the flat spectrum radio quasar PKS 1222+216 from 2008 to 2015 using multi-frequency monitoring which involves γ-ray data from the Fermi Large Area Telescope, total intensity and linear polarization observations from different optical telescopes in R band, and imaging of the inner jet structure with the Very Long Baseline Array (VLBA) at 43 GHz. During the observations, the source showed several dramatic flares at γ rays and optical bands, with the rising branch of a γ-ray flare accompanied by a rapid rotation of the polarization position angle (EVPA), a fast increase of the degree of polarization in the optical band, brightening of the VLBI core, and appearance of a new superluminal component in the parsec-scale jet. The rapid variability of the optical linear polarization may be explained by a strong turbulence in the jet plasma. We find a correlation between the γ rays, optical R band, and 43 GHz variability on a long-term scale (months and years), and a good general alignment between EVPAs in R band and at 43 GHz, while the correlation between short-term variations (days and weeks) is weaker. Synchronous activity across the bands supports the idea that the emission regions responsible for the γ-ray and optical flares are co-spatial and located in the vicinity of the mm-wave core of the parsec-scale jet. However, these connections do not completely explain the challenging behaviour of PKS 1222+216, since there are some γ-ray flares which are not accompanied by jet events, and vice versa. We need a continuation of multi-frequency monitoring along with high resolution imaging of the parsec-scale jet to understand in detail the origin of high energy emission in blazars. View Full-Text
Keywords: blazars; jets; VLBA; polarization blazars; jets; VLBA; polarization
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Troitskiy, I.; Morozova, D.; Jorstad, S.; Larionov, V.; Marscher, A.; Agudo, I.; Blinov, D.; Smith, P.; Troitskaya, Y. Multi-Frequency Monitoring of the Flat Spectrum Radio Quasar PKS 1222+216 in 2008–2015. Galaxies 2016, 4, 72.

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