Abstract:
Blazars are the most luminous persistent objects in the sky.  They exhibit variability across the electromagnetic spectrum on timescales ranging from years to minutes.  Blazars constitute a sub-class of active galactic nuclei (AGN) whose relativistic plasma jets are thought to be closely aligned to our line-of-sight.  The emission from blazars is predominantly non-thermal, including radio synchrotron radiation and X-ray and gamma-ray inverse-Compton scattering.  The central engines of blazars, which are believed to be the ultimate source of this variability, are unresolved and opaque to radio waves.  Hence, they are not imaged directly, even with the 0.1 milliarcsecond (mas) resolution obtained with the Very Long Baseline Array (VLBA).  Despite this limitation, by both monitoring the radio jets and subsequently modeling the flares in the high-energy emission from these AGN, we can potentially gain insight into the parsec-scale physics of the jets close to the central engines.  I will present several theoretical models of high-energy blazar emission.  The ability of these models to reproduce actual multi-wavelength light-curves obtained during flaring events will be scrutinized.  Furthermore, I will present observational support for the plausibility of these models in the form of radio polarimetric data obtained with the VLBA, and with synthetic polarized emission maps produced via ray-tracing algorithms.

Talk Host: Federico Marinacci

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