Time Dependent Leptonic and Lepto-Hadronic Modeling of Blazar Emission

Active galactic nuclei (AGN) are known to exhibit multi-wavelength variability across the whole electromagnetic spectrum. In the context of blazars, the variability timescale can be as short as a few minutes. Correlated variability has been seen in different bands of the electromagnetic spectrum: from radio wavelengths to high energy gamma-rays. This correlated variability in different wavelength bands can put constraints on the particle content, acceleration mechanisms and radiative properties of the relativistic jets that produce blazar emission. Two models are typically invoked to explain the origin of the broadband emission across the electromagnetic spectrum: Leptonic and Hadronic Modeling. Both models have had success in reproducing the broadband spectral energy distributions (SEDs) of blazar emission with different input parameters, making the origin of the emission difficult to determine. However, flaring events cause the spectral components that produce the SED to evolve on different timescales, producing different light curve behavior for both models. My Ph.D. research involves developing one-zone time dependent leptonic and lepto-hadronic codes to reproduce the broadband SEDs of blazars and then model flaring scenarios in order to find distinct differences between the two models. My lepto-hadronic code also considers the time dependent evolution of the radiation emitted by secondary particles (pions and muons) generated from photo-hadronic interactions between the photons and protons in the emission region. I present fits to the broadband SEDs of the flat spectrum radio quasars (FSRQs) 3C 273 and 3C 279 using my one-zone leptonic and lepto-hadronic model, respectively. I showed that by considering perturbations of any one of the selected input parameters for both models: magnetic field, particle injection luminosity, particle spectral index, and stochastic acceleration time scale, distinct differences arise in the light curves for the optical, X-ray and gamma-ray bandpasses that can separate leptonic and lepto-hadronic models. I find that decreasing the stochastic acceleration timescale for a one-zone leptonic model will result in a decrease in flux in the X-ray band as opposed to the lepto-hadronic model, in which an increase is seen. I also find that increasing the magnetic field produces a drop in the X-ray and gamma-ray bands while for the lepto-hadronic model, an increase is observed in both bands. In the final part of my Ph.D. research, I use my leptonic and lepto-hadronic codes to reproduce the SED of the FSRQ 3C 454.3. The SED fits are then used to model a large multi-wavelength flare that 3C 454.3 exhibited in November 2010. I find that a combination of parameter changes to the magnetic field, particle injection luminosity, stochastic acceleration timescale and particle spectral index is needed to model the November flare. Using both codes to model the flare, I found that the lepto-hadronic model can reproduce both the broadband spectral energy distribution of 3C 454.3 in its quiescent and flaring states and can reproduce the integrated light curves in three bandpasses; optical R, Swift XRT and Fermi gamma-rays. I also found that the fits to the SED of 3C 454.3 in its flaring state could not be reproduced by our one-zone leptonic model.