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Today's Colloquium: Blazar jet physics through variability studies and direct imaging

Submitter: Vassilis Karamanavis
Description: Blazars constitute the beamed population of AGN and are the most copious and variable emitters of radiation in the Universe. The detailed processes that give rise to those characteristics though are still under intense debate.
In August 2008, Fermi/LAT discovered the distant blazar PKS 1502+106 (z=1.839) showing a strong gamma-ray outburst, followed by bright and variable flux over the next months. This activity at high energies triggered an intensive multi-wavelength campaign indicating that the outburst was accompanied by a significantly delayed counterpart at radio bands.

Utilizing ultra-high resolution VLBI imaging at 15, 43, and 86 GHz, we attempt to shed light on the physics of the jet flow right after this high-energy flare.

In this talk the findings of the mm-VLBI study, using the Global Millimeter VLBI Array (GMVA), will be presented. Additionally, light curves from the F-GAMMA monitoring program have been employed. The flare was quantified using a Gaussian process regression scheme and a cross-correlation analysis. The observed delays offer a tomography of the jet's opacity structure and allow the accurate localisation of the high-energy emission.
Copyright: Karamanavis et al. 2016, A&A, 586, A60; Karamanavis et al. 2016, A&A 590, A48
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