Graduate Thesis Or Dissertation
 

Radiative Acceleration and Emission from Relativistic Outflows

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/dr26z307b

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  • Outflowing streams of matter or jets are a common phenomenon in the observeduniverse. The most extreme and powerful jets are relativistic, i.e., they travel at speedscomparable to the of speed light. Gamma Ray-Bursts (GRBs) and Active Galactic Nuclei(AGNs) are two sources of these relativistic jets. In this work I will explore the role playedby advected radiation the radiation internal to the jet itself in modifying the jetdynamics and creating the observed radiation spectrum. First, I present a Monte Carlocode designed to simulate the spectrum formed in a scattering dominated photon-leptonplasma. I demonstrate that non-thermal features in the emitted spectrum can arisefrom the interaction of thermal populations of photons and leptons, initially at differenttemperatures. I find the existence of a correlation between the spectral parametersthat suggests the presence of this mechanism in cosmic sources, for example, in promptspectra of GRBs. These simulations, however, do not account for the dynamical couplingbetween the radiation and matter within the jet, which is expected for outflows from bothGRBs and AGNs. In the second part of this dissertation, I show how radiation regulatesthe dynamical properties (such as structure, acceleration) of jets. I use a custom-madedynamic Monte Carlo code to study radiation (Compton scattering) driven expansionand acceleration in unexplored evolutionary stages of GRB jets. My results uncover newregimes of jet evolution and allow me to obtain analytical estimates to better parameterizethe jet dynamics in analytical and semi-analytical studies. In addition, I explore radiativeacceleration and deceleration as mechanisms to produce two-component structured AGNjets. I find that this radiation-driven regulatory mechanism plays a crucial role inexplaining the puzzling observation of high-energy emission from misaligned AGN jets.
  • Keywords: Outflows, Relativistic, AGNs, Jets, Radiation, GRBs
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