Fermi Gamma-ray Space Telescope

Connection between Gamma-ray Activity, Emission Line Variability, and Jet Behavior in Blazars

Svetlana Jorstad
(Alan Marscher, Valeri Larionov, and Karen Williamson)


We have analyzed total and polarized intensity images obtained with the Very Long Baseline Array (VLBA) at 43 GHz for the quasar CTA102 during the dramatic outburst in 2016 December and for the quasar 4C+29.45 (1156+295, Ton 599) during the VHE event in the end of 2017. Using the 4.3 m Discovery Channel Telescope of Lowell Observatory, we have monitored MgII, FeII, and FeIII emission lines of the quasars during the outbursts. In both cases a significant increase of the total and polarized flux in the mm-wave VLBI core contemporaneous with the high energy events has been detected, along with the appearance of superluminal knots in the jets. 10 years of VLBA monitoring of the quasars reveals the existence of quasi-stationary features in the inner parsec-scale jet of the quasars in addition to the VLBI core. Based on the kinematics of the superluminal knots and position of the quasi-stationary features, we connect the structure of the gamma-ray events with propagation of superluminal knots through the core and stationary features. Analysis of properties of the emission lines shows correlated variability between the flux of the emission lines (especially FeIII in CTA102 and FeII in 4C+29.45), optical continuum, and gamma-ray flux that suggests that the jet plays a role in the emission line excitation. We discuss the properties and nature of the enhanced gamma-ray emission, emission line variability, and jet behavior. The research at Boston University is supported by NASA grant 80NSSC17K0649 and NSF grant AST-1615796. The St.Petersburg University group acknowledges support from Russian Science Foundation grant 17-12-01029.