Lisakov, Mikhail

Multifrequency vlbi follow up study of jets in the blazars 3C273 and 3C279 after strong gamma-ray flares.

Author list: Mikhail Lisakov, Yuri Kovalev, Evgeniya Kravchenko

We present results of a five month long VLBA campaign to observe 3C273 and 3C279 between 5 and 43 GHz. This campaign was triggered by and started immediately after a strong gamma-ray flare detected by Fermi LAT from 3C273 in August 2009. In the same time 3C279 was undergoing a period of a high gamma-ray activity. We have detected flares in the parsec-scale radio cores of both 3C273 and 3C279. Flux density of the cores of both AGN at 43 GHz have increased by a factor of 2-3 within several months, while radio spectra became inverted. An ejection of a new born 43 GHz component in 3C273 is measured to happen about 140 days after the strong gamma-ray flare. A close connection between gamma-ray and parsec-scale radio emission in the blazars is supported. Frequency dependent apparent shift of the core position, evolution of linear polarization structure, Faraday RM and its variability as well as spectral properties are also presented and analyzed. Finally we discuss changes in physical properties which occurred in the apparent jet base during the flare.