Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Physics and Astronomy

First Advisor

H. Richard Miller - Chair

Second Advisor

D. Michael Crenshaw

Third Advisor

Douglas R. Gies

Fourth Advisor

William H. Nelson

Fifth Advisor

Paul J. Wiita


The extreme AGN known as blazars can be classified based on their spectral properties into X-ray and radio selected objects, known as XBLs and RBLs, respectively. In this work, the results of new multiwavelength campaigns are presented for two XBLs and two RBLs. Each campaign contains simultaneous observations in the radio, optical, and X-ray regimes. A campaign on a third RBL was completed using near-simultaneous archival radio, optical/IR, and gamma-ray data. The simultaneous multiwavelength behavior exhibited in each campaign was analyzed by examining the multiwavelength variability and using spectral analysis. Observations of prominent optical microvariability were quantitatively analyzed. Previously published results for other blazars were compared to the new and archival results. Many interesting results emerged from these investigations. PG 1553+11, a radio-weak blazar, was found to be an extreme XBL. During three campaigns performed for the XBL PKS 2155-304, different variability behavior was observed each time. In a high flux state, the X-ray behavior was strongly correlated with the optical behavior. In a weak state, the X-ray and optical behaviors were not correlated. In an intermediate state, the X-ray behavior was somewhat correlated with the optical behavior. CTA 102, an RBL, exhibited some of the most extreme optical microvariability ever observed, including a brightening of about 0.07 magnitudes in less than 15 minutes. Surprisingly, the optical spectra of RBLs CTA 102, PKS 1622-297, and 3C 345 were found to become redder when in a brighter flux state. The RBLs all exhibited large amplitude optical microvariability. The campaigns on PG 1553+11, CTA 102, and PKS 1622-297 were the first simultaneous multiwavelength campaigns performed for these objects. For objects in which the results of at least two campaigns were available, including PKS 2155-304, correlations that appeared to be present at one epoch seemed to vanish at other times. The SSC model represented many of the observations well. Color studies of the selected BL Lac objects found them to be bluer when brighter, while the selected FSRQs were found to be redder when brighter. These results provide strong motivation for future multiwavelength campaigns that provide broader wavelength and more extensive temporal coverage.