A 5.3-minute-period pulsing white dwarf in a binary detected from radio to X-rays

TL;DR

This paper reports the discovery of a new white dwarf binary system with pulsating emission, expanding the class of known white dwarf pulsars and supporting existing formation theories.

Contribution

It introduces the first known binary white dwarf pulsar with a 5.3-minute period, confirming the existence of this class and aiding understanding of their formation.

Findings

Discovery of a new white dwarf pulsar binary system.

Pulsation period of 5.30 minutes observed.

Supports models of white dwarf pulsar formation.

Abstract

White dwarf stars are the most common stellar fossils. When in binaries, they make up the dominant form of compact object binary within the Galaxy and can offer insight into different aspects of binary formation and evolution. One of the most remarkable white dwarf binary systems identified to date is AR Scorpii (henceforth AR Sco). AR Sco is composed of an M-dwarf star and a rapidly-spinning white dwarf in a 3.56-hour orbit. It shows pulsed emission with a period of 1.97 minutes over a broad range of wavelengths, which led to it being known as a white dwarf pulsar. Both the pulse mechanism and the evolutionary origin of AR Sco provide challenges to theoretical models. Here we report the discovery of the first sibling of AR Sco, J191213.72-441045.1 (henceforth J1912-4410), which harbours a white dwarf in a 4.03-hour orbit with an M-dwarf and exhibits pulsed emission with a period of 5.30 minutes. This discovery establishes binary white dwarf pulsars as a class and provides support for proposed formation models for white dwarf pulsars.