A1 Refereed original research article in a scientific journal
LOCATION OF gamma-RAY FLARE EMISSION IN THE JET OF THE BL LACERTAE OBJECT OJ287 MORE THAN 14 pc FROM THE CENTRAL ENGINE
Authors: Agudo I, Jorstad SG, Marscher AP, Larionov VM, Gomez JL, Lahteenmaki A, Gurwell M, Smith PS, Wiesemeyer H, Thum C, Heidt J, Blinov DA, D'Arcangelo FD, Hagen-Thorn VA, Morozova DA, Nieppola E, Roca-Sogorb M, Schmidt GD, Taylor B, Tornikoski M, Troitsky IS
Publisher: IOP PUBLISHING LTD
Publication year: 2011
Journal:Astrophysical Journal Letters
Journal name in sourceASTROPHYSICAL JOURNAL LETTERS
Journal acronym: ASTROPHYS J LETT
Article number: ARTN L13
Number in series: 1
Volume: 726
Issue: 1
Number of pages: 6
ISSN: 2041-8205
DOI: https://doi.org/10.1088/2041-8205/726/1/L13
We combine time-dependent multi-waveband flux and linear polarization observations with submilliarc-second-scale polarimetric images at gimel = 7 mm of the BL Lacertae type blazar OJ287 to locate the gamma-ray emission in prominent flares in the jet of the source > 14 pc 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 millimeter-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 millimeter-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 millimeter-wave flares are cospatial and occur > 14 pc from the central engine. We also associate two optical flares, accompanied by sharp polarization peaks, with the two. -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 millimeter-wave polarization is high at the onset of a flare, but decreases as the electrons emitting at these wavelengths penetrate less polarized regions.
