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Title:
The ever-surprising blazar OJ 287: multiwavelength study and appearance of a new component in X-rays
Authors:
Kushwaha, Pankaj; Gupta, Alok C.; Wiita, Paul J.; Pal, Main; Gaur, Haritma; de Gouveia Dal Pino, E. M.; Kurtanidze, O. M.; Semkov, E.; Damljanovic, G.; Hu, S. M.; Uemura, M.; Vince, O.; Darriba, A.; Gu, M. F.; Bachev, R.; Chen, Xu; Itoh, R.; Kawabata, M.; Kurtanidze, S. O.; Nakaoka, T.; Nikolashvili, M. G.; Sigua, L. A.; Strigachev, A.; Zhang, Z.
Affiliation:
AA(Department of Astronomy (IAG-USP), University of Sao Paulo, Sao Paulo 05508-090, Brazil 0000-0001-6890-2236), AB(Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India; Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China 0000-0002-9331-4388), AC(Department of Physics, The College of New Jersey, PO Box 7718, Ewing, NJ 08628-0718, USA), AD(Astronomy & Astrophysics Division, Physical Research Laboratory, Ahmedabad 380009, India), AE(Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India), AF(Department of Astronomy (IAG-USP), University of Sao Paulo, Sao Paulo 05508-090, Brazil), AG(Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia; Engelhardt Astronomical Observatory, Kazan Federal University, Tatarstan 420008, Russia; Center for Astrophysics, Guangzhou University, Guangzhou 510006, China; Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China), AH(Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko Shosse Blvd., 1784 Sofia, Bulgaria), AI(Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia), AJ(Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai 264209, China), AK(Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan), AL(Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia), AM(American Association of Variable Star Observers (AAVSO), 49 Bay State Rd., Cambridge, MA 02138, USA; Group M1, ​Centro Astronómico de Avila. Paseo del Pintor Rosales, 14 - Piso 2 Izq. 28008 Madrid, Spain), AN(Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China), AO(Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko Shosse Blvd., 1784 Sofia, Bulgaria), AP(Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai 264209, China), AQ(Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan), AR(Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan), AS(Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia), AT(Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526, Japan), AU(Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia), AV(Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia), AW(Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72 Tsarigradsko Shosse Blvd., 1784 Sofia, Bulgaria), AX(Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China)
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 479, Issue 2, p.1672-1684 (MNRAS Homepage)
Publication Date:
09/2018
Origin:
OUP
Astronomy Keywords:
radiation mechanisms: non-thermal, galaxies: active, BL Lacertae objects: individual: OJ 287, galaxies: jets, gamma-rays: galaxies, X-rays: galaxies
Abstract Copyright:
2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
DOI:
10.1093/mnras/sty1499
Bibliographic Code:
2018MNRAS.479.1672K

Abstract

We present a multiwavelength spectral and temporal investigation of OJ 287 emission during its strong optical-to-X-ray activity between 2016 July and 2017 July. The daily gamma-ray fluxes from Fermi-Large Area Telescope (LAT) are consistent with no variability. The strong optical-to-X-ray variability is accompanied by a change in power-law spectral index of the X-ray spectrum from <2 to >2, with variations often associated with changes in optical polarization properties. Cross-correlations between optical-to-X-ray emission during four continuous segments show simultaneous optical-ultraviolet (UV) variations, while the X-ray and UV/optical are simultaneous only during the middle two segments. In the first segment, the results suggest X-rays lag the optical/UV, while in the last segment X-rays lead by ˜5-6 d. The last segment also shows a systematic trend with variations appearing first at higher energies followed by lower energy ones. The LAT spectrum before the very high-energy (VHE) activity is similar to preceding quiescent state spectrum, while it hardens during VHE activity period and is consistent with the extrapolated VHE spectrum during the latter. Overall, the broad-band spectral energy distributions (SEDs) during high-activity periods are a combination of a typical OJ 287 SED and a high-energy peaked (HBL) SED and can be explained in a two-zone leptonic model, with the second zone located at parsec scales, beyond the broad line region, being responsible for the HBL-like spectrum.The change of polarization properties from systematic to chaotic and back to systematic, before, during, and after the VHE activity, suggests dynamic roles for magnetic fields and turbulence.
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