by Dr. Margaret Ridder
Thesis defended on August 28, 2025
Department of Physics, University of Alberta
Thesis advisor: Prof. Craig Henke
Abstract:
Cataclysmic variables (CVs) are binary systems in which a white dwarf accretes from a low-mass donor star via Roche lobe overflow. They have been studied for well over a century, but the origin of their radio emission remains uncertain. In this thesis, I present the discovery of two unusual CVs in the Very Large Array Sky Survey (VLASS): QS Vir, a low-accretion rate pre-CV, and V2400 Oph, a diskless intermediate polar. In addition, I conduct follow-up radio and X-ray observations of QS Vir, finding two highly circularly polarized radio flares, which I attribute to a coherent plasma emission process such as electron-cyclotron maser emission or plasma radiation. Finally, I perform spectral, temporal, and polarization analysis on a sample of 6 other CVs at higher frequencies. I find a total of three flare events with high fractional circular polarization from two CVs, and find steady, spectrally steep radio emission from V2400 Oph. For most CVs, we see a flat gyrosynchrotron component that is at times accompanied by a coherent, flaring component for most CVs. The only CV that exhibits a synchrotron-like spectrum in this thesis is V2400 Oph.