Physics
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21330601c&link_type=abstract
American Astronomical Society, AAS Meeting #213, #306.01; Bulletin of the American Astronomical Society, Vol. 41, p.276
Physics
Scientific paper
Due to their large distances, AGNs are not spatially resolved with current and near-future technologies except by radio interferometry. However, we can use time variability, one of the defining properties of AGNs, to probe the location and physical processes related to the emission at resolutions even finer than provided by VLBI. I use extensive multi-frequency monitoring data of the blazars 3C 279 and PKS 1510-089 (over 10 years long) and the radio galaxy 3C 120 ( 5 years), including well-sampled light curves (radiative flux vs. time) at X-ray energies (2-10 keV), optical wavelengths (R band), and radio frequencies (14.5 GHz and 37 GHz), as well as monthly images obtained with the Very Long Baseline Array (VLBA) at 43 GHz that follow changes in the emission structure of the jet on parsec scales. I have developed and applied a set of statistical tools to characterize the time variability of AGNs. This includes the power spectral density (PSD) and its uncertainties, discrete cross-correlation functions and their significance using random light curves simulated from the previously calculated PSDs, and decomposition of light curves into individual flares. I also model the time variable emission spectrum of an AGN jet using a numerical code that includes conical geometry, turbulent magnetic field and density, and energization of electrons due to a moving shock front. Comparing the results of the model calculations and the application of the above-mentioned statistical procedures on the real data, I draw conclusions about the location of the emission regions of these objects. I also identify the ongoing emission mechanisms and implications regarding the physics of jets.
This work is supported by NASA through grants NNX08AJ64G (ADP) and NNX08AV65G (Fermi).
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