Search for gamma-ray emission from the white dwarf pulsar system AR Sco using the Pass 8 Fermi-LAT data

Abstract

AR Sco is a close compact binary system that shows non-thermal, pulsed and highly linear polarized emission. In this study, a search for high energy gamma-ray emission was conducted between 100 MeV - 500 GeV by analysing the newly available Fermi-LAT Pass 8 data with the new Fermi 1.0.1 Science Tools. Binned likelihood analysis was performed using power law, broken power law and log parabola models. From the selected Region of Interest (ROI) centred on AR Sco’s position, we calculated a statistical significance of √TS ≤ 4.31σ for the integrated gamma-ray activity between 100 MeV - 500 GeV at a photon flux level of (4.39 ± 3.24) x 10^−9 ph cm^−2 s^−1 using the broken power law model. This resulted in a 2σ upper-limit detection from the position of AR Sco. Unbinned likelihood analysis was also done to maximize the probability of detection from this faint gamma-ray emitting region, resulting in a statistical √TS ≤ 3.69σ using a broken power law model with an associated photon flux level of (3.05 ± 1.60) x 10^−9 ph cm^−2 s^−1.