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APPARENT INWARD MOTION OF THE PARSEC-SCALE JET IN THE BL LAC OBJECT OJ287 DURING THE 2011-2012 γ-ray FLARES

  • SAWADA-SATOH, S. (Mizusawa VLBI Observatory, NAOJ) ;
  • AKIYAMA, K. (The University of Tokyo) ;
  • NIINUMA, K. (Yamaguchi University) ;
  • NAGAI, H. (NAOJ) ;
  • KINO, M. (KASI) ;
  • D'AMMANDO, F. (INAF Istituto di Radioastronomia) ;
  • KOYAMA, S. (Max-Planck-Institut fur Radioastronomie) ;
  • HADA, K. (NAOJ) ;
  • ORIENTI, M. (INAF Istituto di Radioastronomia) ;
  • HONMA, M. (NAOJ) ;
  • SHIBATA, K.M. (NAOJ)
  • Received : 2014.11.30
  • Accepted : 2015.06.30
  • Published : 2015.09.30

Abstract

We present a kinematic study of the parsec-scale radio jet in OJ 287, one of the most studied BL Lac objects, during ${\gamma}$-ray flares, to explore the relation between parsec-scale radio jet activity and ${\gamma}$-ray emission. The 22-GHz light curve of OJ 287 show three obvious flare events around 2011 May, 2011 October, and 2012 March. The second radio flare occurred during the ${\gamma}$-ray flaring period, and the third radio flare seemed to precede the ${\gamma}$-ray flare by one month. One jet component moved outward with respect to the core component with an apparent superluminal speed (~ 11c) from 2010 November to 2011 November. Then it changed direction, moving apparently inward in 2011 November, when the ${\gamma}$-ray flare occurred. The observed apparent inward motion of the jet at 22 GHz could be caused by a new jet component, unresolved at 22 GHz, in the innermost region.

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