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arXiv · 1011.6454

Location of gamma-ray Flare Emission in the Jet of the BL Lacertae Object OJ287 more than 14pc from the Central Engine

Ivan Agudo·Svetlana G. Jorstad·Alan P. Marscher·Valeri M. Larionov·Jose L. Gomez·Anne Lahteenmaki·Mark A. Gurwell·Paul S. Smith·Helmut Wiesemeyer·Clemens Thum·Jochen Heidt·Dmitriy A. Blinov·Francesca D. D'Arcangelo·Vladimir A. Hagen-Thorn·Daria A. Morozova·Elina Nieppola·Mar Roca-Sogorb·Gary D. Schmidt·Brian Taylor·Merja Tornikoski·Ivan S. Troitsky
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Abstract

We combine time-dependent multi-waveband flux and linear polarization observations with sub-milliarcsecond-scale polarimetric images at lambda=7mm of the BL Lacertae-type blazar OJ287 to locate the gamma-ray emission in prominent flares in the jet of the source >14pc from the central engine. We demonstrate a highly significant correlation between the strongest gamma-ray and millimeter-wave flares through Monte-Carlo simulations. The two reported gamma-ray peaks occurred near the beginning of two major mm-wave outbursts, each of which is associated with a linear polarization maximum at millimeter wavelengths. Our Very Long Baseline Array observations indicate that the two mm-wave flares originated in the second of two features in the jet that are separated by >14 pc. The simultaneity of the peak of the higher-amplitude gamma-ray flare and the maximum in polarization of the second jet feature implies that the gamma-ray and mm-wave flares are co-spatial and occur >14 pc from the central engine. We also associate two optical flares, accompanied by sharp polarization peaks, with the two gamma-ray events. The multi-waveband behavior is most easily explained if the gamma-rays arise from synchrotron self-Compton scattering of optical photons from the flares. We propose that flares are triggered by interaction of moving plasma blobs with a standing shock. The gamma-ray and optical emission is quenched by inverse Compton losses as synchrotron photons from the newly shocked plasma cross the emission region. The mm-wave polarization is high at the onset of a flare, but decreases as the electrons emitting at these wavelengths penetrate less polarized regions.

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Ivan Agudo, Svetlana G. Jorstad, Alan P. Marscher, Valeri M. Larionov, Jose L. Gomez, Anne Lahteenmaki, Mark A. Gurwell, Paul S. Smith, Helmut Wiesemeyer, Clemens Thum, Jochen Heidt, Dmitriy A. Blinov, Francesca D. D'Arcangelo, Vladimir A. Hagen-Thorn, Daria A. Morozova, Elina Nieppola, Mar Roca-Sogorb, Gary D. Schmidt, Brian Taylor, Merja Tornikoski, Ivan S. Troitsky. 2010-11-30. Location of gamma-ray Flare Emission in the Jet of the BL Lacertae Object OJ287 more than 14pc from the Central Engine. https://doi.org/10.1088/2041-8205%2F726%2F1%2Fl13

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