Abstract
We present multi-wavelength studies of the radio galaxy 3C 120 and the blazar CTA 102 during unprecedented γ-ray flares for both sources. In both studies the analysis of γ-ray data has been compared with a series of 43 GHz VLBA images from the VLBA-BU-BLAZAR program, providing the necessary spatial resolution to probe the parsec scale jet evolution during the high energy events. To extend the radio dataset for 3C 120 we also used 15 GHz VLBA data from the MOJAVE sample. These two objects which represent very different classes of AGN, have similar properties during the γ-ray events. The γ-ray flares are associated with the passage of a new superluminal component through the mm VLBI core, but not all ejections of new components lead to γ-ray events. In both sources γ-ray events occurred only when the new components are moving in a direction closer to our line of sight. We locate the γ-ray dissipation zone a short distance from the radio core but outside of the broad line region, suggesting synchrotron self-Compton scattering as the probable mechanism for the γ-ray production.
Highlights
The majority of active galactic nuclei (AGN) detected at γ-ray energies are blazars, as expected from the orientation of their jets that point closer to our line of sight, and only a few percentage are radio galaxies
For CTA 102 we extended the study to the entire electromagnetic spectrum, collecting data from many ground telescopes and satellites
In the case of CTA 102, which displayed in September 2012 a bright γ-ray outburst in coincidence with flares at optical and NIR wavelengths, we studied the source in the entire electromagnetic spectrum
Summary
The majority of active galactic nuclei (AGN) detected at γ-ray energies are blazars, as expected from the orientation of their jets that point closer to our line of sight, and only a few percentage are radio galaxies. Telescope (LAT) on board the Fermi satellite on 24 September 2014 from the radio galaxy 3C 120 [1], was an unexpected event This bright flare seems associated with a prolonged γ-ray activity from the source that started in December 2012 and lasted until at least October 2014, which corresponds to our last data analyzed. The blazar CTA 102 is more often observed in a quiescent state, leading to an average γ-ray flux rather low (∼5 × 10−9 photon cm−2 s−1 , 1 < E < 100 GeV), as reported in the third Fermi catalog [2] Occasionally this source shows bright γ-ray outbursts where it increases its daily flux by three orders of magnitude or more. We describe the main results achieved focusing the attention on the common properties displayed by these two sources during the high-energy events, despite belonging to two different classes of AGN
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