The search for high-energy gamma-ray emission from the close binary system AR Scorpii using Fermi-LAT data
University of the Free State
AR Scorpii (AR Sco) is an enigmatic close binary system which is observable across most of the electromagnetic spectrum. Multi-wavelength emission consists of both thermal and non-thermal components, where pulsed non-thermal emission has been observed from radio to X-ray. The apparent lack of accretion in the system also suggests that the highly magnetic white dwarf is primarily spin-powered, similar to pulsars, where particles can be accelerated to produce non-thermal emission. The multi-wavelength nature from radio to X-ray of AR Sco has been extensively studied and presented since 2016, showing a clear non-thermal synchrotron component from optical to X-ray. However, the parameters and processes towards the high-energy regime still need to be clearly verified and explored. Hence, a search for non-thermal γ-ray emission from AR Sco using archival Fermi data from the past decade has been performed. By using updated Fermi-LAT software and Pass 8 analysis methods, low-level upper-limit emission has been observed above 100 MeV, with a possible low-level pulsed signal at the spin period (Ps = 117 s) of the white dwarf. Given the results, the possibility of non-thermal emission at higher energies can not be excluded. An updated spectral energy distribution using Fermi-LAT data was also produced to serve as a template for future studies using more sensitive Cherenkov telescope detectors like e.g. the Cherenkov Telescope Array (CTA).
High-energy emission, Non-thermal emission, Fermi γ-ray space telescope, 4FGL, Pass 8, Likelihood analysis, Time-series analysis, Cataclysmic variable star, star - AR Sco, Dissertation (M.Sc. (Physics))--University of the Fee State, 2021