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Time-Dependent Studies of High-Energy Radiation from Blazars

Date of Award

Winter 12-15-2012

Author's School

Graduate School of Arts and Sciences

Author's Department


Degree Name

Doctor of Philosophy (PhD)

Degree Type



We have used X-ray and both GeV and TeV gamma-ray temporal data to conduct a probe into possible Lorentz invariance violation dispersion effects, as well as to look into possible correlations between different energy bands in blazar emission.

Some quantum gravity models predict a breaking of Lorentz invariance at an energy level, E_QG, generally thought to be close to the Planck energy, which may result in energy-dependent corrections to the photon dispersion relation. By using the ground-based gamma-ray telescope VERITAS to look at the arrival times of high-energy radiation from a large flare from the blazar Mrk 421, we have been able to place strong constraints on E_QG, assuming both a linear correction and a quadratic correction to the standard dispersion relation.

Our search for Lorentz invariance violation assumed the simultaneous emission of different energy radiation by the source. This assumption can be tested by modeling particle acceleration and emission processes. To help identify relevant processes, we looked for potential correlations between X-ray data (from the Swift-XRT satellite) and GeV gamma-ray data (from the Fermi-LAT satellite) using the discrete correlation function (DCF). By applying the DCF to 6 different blazars, we have found no correlations between X-ray and GeV gamma-ray emission. The finding does not bolster, but is consistent with, leptonic models, in which electrons of different energies produce the X-ray and gamma-ray emission in inverse-Compton processes.


English (en)

Chair and Committee

Henric Krawczynski

Committee Members

James Buckley, Roger Chamberlain, Ramanath Cowsik, Martin Israel, Jill Pasteris


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