In Like a Lamb, Out Like a Lion: Probing the Disk-Jet Connection in Fermi Gamma-ray Bright Blazars

Blazars are active galactic nuclei whose relativistic jet is aligned at small angles (< 5°) with respect to the Earth line of sight. Their broadband emission is generally jet-dominated, but during quiescent periods the thermal contribution can often still be detected, making them an ideal laboratory to study the energetics of infalling and outflowing material. The simultaneously obtained multiwavelength, long-term data analyzed here help to better evaluate the impact of jet power on the broadband spectral energy distributions of these sources via the OIR color variability analysis. Secondly, emission line variability studies presented here can help constrain the location of the gamma-emitting region as well set preliminary constraints on the minimum jet contribution necessary to significantly increase the photoionizing flux in the broad line region. I briefly discuss the main findings of this dissertation below.;The optical and infrared (OIR) light curves and color variability diagrams for a sample of 12 blazars are presented. I analyze the OIR color variability of these blazars from 2011 - 2013, comparing their OIR properties to the jet state via Fermi gamma-ray fluxes obtained on a similar cadence. This project also assesses long-term color variability by extending the temporal baseline of 6 blazars to 5 years, allowing the comparison of the color variability in the same source at different jet states. Using the slope of the color variability diagram, we propose that the existing dichotomy between FSRQ (redder when brighter) and BLL (bluer when brighter) color variability be reconsidered as a continuum of jet (versus disk) activity, in which blazars can achieve either color variability response depending on jet power. This allows a self-consistent description of the changes in OIR color variability in the same source over time, as well as the OIR color variability in a sample of blazars over time.;The second topic of the dissertation is the emission line variability properties of a sample of 7 blazars. We compare the emission line variability with Fermi gamma-ray flux and optical linear polarized flux to estimate its relationship to jet activity. In general, the emission line fluxes are much less variable than the continuum; 4 of the 7 sources had no emission line variability over ~5 year timescales. This implies that the variability in the jet and in the disk are relatively independent and that the jet emission is likely caused by internal processes, rather than increased accretion. However, 3C 454.3, PKS 1510-089 and PKS 0454-234 showed statistically significant emission line variability, with a mean line flare significance of ~ 4sigma, in close temporal proximity to Fermi gamma-ray flares. While 3C 454.3 and PKS 1510-089 are the two brightest Fermi gamma-ray flaring blazars, we use the peak Fermi gamma-ray flux in PKS 0454-234 to suggest a threshold gamma-ray flux, above which the jet is depositing enough energy in the broad line region to appreciably increase the photoionizing flux seen by the broad line region; below this threshold gamma-ray flux the jet is either not producing enough photoionizing flux to sufficiently energize the broad line region or the jet emitting region is outside of the broad line region.