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http://hdl.handle.net/20.500.12386/23566
Title: | Discovery of a Highly Polarized Optical Microflare in Blazar S5 0716+714 during the 2014 WEBT Campaign | Authors: | Bhatta, G. Goyal, A. Ostrowski, M. Stawarz, Ł. Akitaya, H. Arkharov, A. A. Bachev, R. Benítez, E. Borman, G. A. Carosati, D. Cason, A. D. Damljanovic, G. Dhalla, S. FRASCA, Antonio Hu, S. -M. Itoh, R. Jorstad, S. Jableka, D. Kawabata, K. S. Klimanov, S. A. Kurtanidze, O. Larionov, V. M. Laurence, D. LETO, Giuseppe Markowitz, A. Marscher, A. P. Moody, J. W. Moritani, Y. Ohlert, J. M. DI PAOLA, Andrea RAITERI, Claudia Maria Rizzi, N. Sadun, A. C. Sasada, M. Sergeev, S. Strigachev, A. Takaki, K. Troitsky, I. S. Ui, T. VILLATA, Massimo Vince, O. Webb, J. R. Yoshida, M. Zola, S. Hiriart, D. |
Issue Date: | 2015 | Journal: | THE ASTROPHYSICAL JOURNAL LETTERS | Number: | 809 | Issue: | 2 | First Page: | 1 | Abstract: | The occurrence of low-amplitude flux variations in blazars on hourly timescales, commonly known as microvariability, is still a widely debated subject in high-energy astrophysics. Several competing scenarios have been proposed to explain such occurrences, including various jet plasma instabilities leading to the formation of shocks, magnetic reconnection sites, and turbulence. In this Letter, we present the results of our detailed investigation of a prominent, five-hour-long optical microflare detected during the recent WEBT campaign on 2014 March 2-6 targeting the blazar 0716+714. After separating the flaring component from the underlying base emission continuum of the blazar, we find that the microflare is highly polarized, with the polarization degree ̃(40-60)% ± (2-10)% and the electric vector position angle ̃(10-20)° ± (1-8)° slightly misaligned with respect to the position angle of the radio jet. The microflare evolution in the (Q,U) Stokes parameter space exhibits a looping behavior with a counterclockwise rotation, meaning the polarization degree decreases with the flux (but is higher in the flux decaying phase), and an approximately stable polarization angle. The overall very high polarization degree of the flare, its symmetric flux rise and decay profiles, and also its structured evolution in the Q-U plane all imply that the observed flux variation corresponds to a single emission region characterized by a highly ordered magnetic field. As discussed in the paper, a small-scale but strong shock propagating within the outflow, and compressing a disordered magnetic field component, provides a natural, though not unique, interpretation of our findings. The data collected by the WEBT Collaboration are stored in the WEBT archive; for questions regarding their availability, please contact the WEBT President Massimo Villata . | Acknowledgments: | The authors acknowledge support from the following grants and institutions: the Polish National Science Centre grants DEC-2012/04/A/ST9/00083 (G.B., A.G., M.O., Ł.S.) and 2013/09/B/ST9/ 00599 (S.Z.); National Natural Science Foundation of China grant 11203016 (S.-M.H.); the Russian RFBR grants 15-02-00949 and 15-32-50887, and St. Petersburg University research grant 6.38.335.2015 (St. Petersburg University team); project FR/639/6-320/12 by the Shota Rustaveli National Science Foundation under contract 31/76 (Abastumani team); the observing grant support from the Institute of Astronomy and Rozhen National Astronomical Observatory, Bulgarian Academy of Sciences, and project Nos. 176011, 176004, and 176021 supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (G.D. and O.V.); NASA under Fermi Guest Investigator grant NNX14AQ58G (BU group). AZT-24 observations are made within an agreement between Pulkovo, Rome and Teramo observatories. | URI: | http://hdl.handle.net/20.500.12386/23566 | URL: | https://iopscience.iop.org/article/10.1088/2041-8205/809/2/L27 | ISSN: | 2041-8205 | DOI: | 10.1088/2041-8205/809/2/L27 | Bibcode ADS: | 2015ApJ...809L..27B | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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