A Model of White Dwarf Pulsar AR Scorpii

TL;DR

This paper presents a model explaining the pulsating emission of AR Scorpii, a white dwarf-M dwarf binary, by proposing a nearly perpendicular rotator white dwarf with a bow shock accelerating electrons, accounting for its broad-band emission.

Contribution

The paper introduces a novel model of AR Scorpii as a nearly perpendicular rotator white dwarf with a bow shock, explaining its pulsating emission across multiple wavelengths.

Findings

Synchrotron radiation from shock-accelerated electrons explains broad-band emission.

The white dwarf's rotation and magnetic geometry produce observed pulsations.

Model reproduces spectral and temporal features of AR Scorpii.

Abstract

A 3.56-hour white dwarf (WD) - M dwarf (MD) close binary system, AR Scorpii, was recently reported to show pulsating emission in radio, IR, optical, and UV, with a 1.97-minute period, which suggests the existence of a WD with a rotation period of 1.95 minutes. We propose a model to explain the temporal and spectral characteristics of the system. The WD is a nearly perpendicular rotator, with both open field line beams sweeping the MD stellar wind periodically. A bow shock propagating into the stellar wind accelerates electrons in the wind. Synchrotron radiation of these shocked electrons can naturally account for the broad-band (from radio to X-rays) spectral energy distribution of the system.