A MULTI-WAVELENGTH POLARIMETRIC STUDY OF THE BLAZAR CTA 102 DURING A GAMMA-RAY FLARE IN 2012

作者：Casadio Carolina^*; Gomez Jose L; Jorstad Svetlana G; Marscher Alan P; Larionov Valeri M; Smith Paul S; Gurwell Mark A; Laehteenmaeki Anne; Agudo Ivan; Molina Sol N; Bala Vishal; Joshi Manasvita; Taylor Brian; Williamson Karen E; Arkharov Arkady A; Blinov Dmitry A; Borman George A; Di Paola Andrea; Grishina Tatiana S; Hagen Thorn Vladimir A; Itoh Ryosuke; Kopatskaya Evgenia N; Larionova Elena G; Larionova Liudmila V; Morozova Daria A

来源：Astrophysical Journal, 2015, 813(1): 51.

DOI：10.1088/0004-637X/813/1/51

• galaxies: active
• galaxies: jets
• quasars: individual (CTA 102)
• techniques: interferometric
• techniques: photometric
• techniques: polarimetric

We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright gamma-ray outburst detected by the Fermi Large Area Telescope in 2012 September-October when the source reached a flux of F->100 MeV = 5.2 +/- 0.4 x 10(-6) photons cm(-2) s(-1). At the same time, the source displayed an unprecedented optical and near-infrared (near-IR) outburst. We study the evolution of the parsec-scale jet with ultra-high angular resolution through a sequence of 80 total and polarized intensity Very Long Baseline Array images at 43 GHz, covering the observing period from 2007 June to 2014 June. We find that the gamma-ray outburst is coincident with flares at all the other frequencies and is related to the passage of a new superluminal knot through the radio core. The powerful gamma-ray emission is associated with a change in direction of the jet, which became oriented more closely to our line of sight (theta similar to 1 degrees.2) during the ejection of the knot and the gamma-ray outburst. During the flare, the optical polarized emission displays intra-day variability and a clear clockwise rotation of electric vector position angles (EVPAs), which we associate with the path followed by the knot as it moves along helical magnetic field lines, although a random walk of the EVPA caused by a turbulent magnetic field cannot be ruled out. We locate the gamma-ray outburst a short distance downstream of the radio core, parsecs from the black hole. This suggests that synchrotron self-Compton scattering of NIR to ultraviolet photons is the probable mechanism for the gamma-ray production.

• 出版日期2015-11-1