Thesis Defense: Relativistic Jets in the Era of X-ray Polarimetry

Mar 01, 2023 - 3:00 pm to 4:00 pm

Campus, Allen 101X

Abel Lawrence Peirson V (KIPAC) In Person and zoom

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Ph.D. Candidate: Abel Lawrence Peirson V
Research Advisor:
Roger W. Romani

Measuring X-ray polarization has been a major goal in astrophysics for the last 40 years. With the launch of NASA's Imaging X-ray Polarimetry Explorer (IXPE) in December 2021, soft X-ray polarimetry (1-10 keV) is now possible. In this talk, I introduce an optimal signal extraction method for X-ray polarimeters based on gas pixel detectors. Using IXPE's thus improved sensitivity, I make progress towards identifying the high-energy emission processes and magnetic field geometries responsible for radiation in blazar jets. First, I develop a simulation-based inference framework for measuring X-ray polarization as a function of time, energy, and position in gas pixel detectors, proving that for a fixed model budget the framework is optimal. Second, I propose a simple geometrical jet model to study the polarization properties of leptonic blazar jets, including their observed EVPA rotations and their detection prospects with IXPE. Finally, I interpret IXPE's measurements of BL Lacertae across the synchro-Compton transition region to suggest leptonic-dominated emission processes in blazars, and of Mrk 421 to provide evidence for helical magnetic fields as the source of EVPA rotations.