Modelling the broadband emission from the white dwarf binary system AR Scorpii

Abstract

In this work, we have analyzed the $\gamma$-ray data in the energy range 100 MeV to 500 GeV from the \emph{Fermi}-Large Area Telescope (LAT) observations for the period August 4, 2008 to March 31, 2019. The $\gamma$-ray emission from AR Scorpii over the last decade is not statistically significant and therefore 2$\sigma$ upper limit on the integral flux above 100 MeV has been estimated. We reproduce the non-thermal broadband spectral energy distribution of AR Scorpii using an emission model having two synchrotron components due to the relativistic electrons in very high magnetic fields. The first component (Synchrotron-1) broadly describes the emissions at radio to high energy X-rays through the synchrotron radiation originating from a spherical region of radius $\sim$ 1.8$\times$10${}^{10}$ cm and a magnetic field strength of $\sim$ 10${}^3$ Gauss. The second component (Synchrotron-2) which reproduces the X-ray emission at lower energies and predicts the $\gamma$-ray emission, originates from another spherical region with radius $\sim$ 1.4$\times$10${}^{10}$ cm and a magnetic field strength of $\sim$ 10${}^6$ Gauss. The relativistic electron populations in both the emission regions are described by a smooth broken power law energy distribution. The $\gamma$-ray emission predicted by the Synchrotron-2 model is below the broadband sensitivity of the \emph{Fermi}-LAT and is also consistent with the 95$\%$ confidence level upper limit on the integral flux above 100 MeV derived from more than 10 years of observations. According to our model, the binary system AR Scorpii could be a $\gamma$-ray source, although its emission level must be below the current detection limit of the \emph{Fermi}-LAT.

15 Pages, 2 Figures, 1 Table, Accepted for Publication in Astroparticle Physics

References in corpus (8)

• A radio pulsing white dwarf binary star
• Properties of the Galactic population of cataclysmic variables in hard X-rays
• AR Sco: A White Dwarf Synchronar
• Extending the Event-weighted Pulsation Search to Very Faint Gamma-ray Sources
• A Model for AR~Scorpii: Emission from Relativistic Electrons Trapped by Closed Magnetic Field Lines of Magnetic White Dwarfs
• Pulsar gamma-ray emission in the radiation reaction regime
• Driving the Beat: Time-Resolved Spectra of the White Dwarf Pulsar AR Scorpii
• On the Polarized Nonthermal Emission from AR Scorpii

Cited by in corpus (2)

• Peeking Between the Pulses: The Far-UV Spectrum of the Previously Unseen White Dwarf in AR Scorpii
• An X-ray study for white dwarf binary AR Scorpii