Monte Carlo/Fokker-Planck simulations of accretion phenomena and optical spectra of BL Lacertae objects

A time-dependent two-dimensional Monte Carlo/Fokker-Planck (MC/FP) code, which uses a Monte Carlo technique for Compton scattering and radiative transport, and a Fokker-Planck technique for electron evolution, has been fully parallelized with the Message Passing Interface (MPI) to take advantage of computers with multiple processors and decrease running time. This code has been successfully applied to the following astrophysically relevant scenario: it was coupled with the line transfer program XSTAR to simulate multiple Compton reflections within photon bubbles, making predictions for their X-ray spectral features. Predictions include a spectral feature at ∼9 keV and hard power-law tails similar to those observed in X-ray binaries in the very high state.; This dissertation also includes the results of an observational project to determine the redshifts of six BL Lac objects, (i.e., galaxies dominated by radiation from the jets emerging from their central black holes) with the 2.4 m Hiltner telescope at the MDM observatory on Kitt Peak, Arizona. The redshifts of these objects have been constrained in agreement with previous estimates in most cases; however, in one case (W Comae) the constraints and previous estimates were not in agreement.