Magnetars and White Dwarf Pulsars

TL;DR

This paper explores the possibility that some pulsars, traditionally thought to be neutron stars with extremely strong magnetic fields, could instead be white dwarf stars with moderate magnetic fields, explaining certain observed anomalies.

Contribution

It proposes an alternative white dwarf pulsar model for AXPs and SGRs, challenging the traditional magnetar interpretation and aligning with recent observations of low magnetic field SGRs/AXPs and magnetic white dwarfs.

Findings

White dwarf pulsars can have magnetic fields of 10^7-10^10 G.

White dwarf pulsars can rotate with periods of 2-12 seconds.

The model explains low magnetic field SGRs/AXPs and fast white dwarfs.

Abstract

The Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely $B\gtrsim10^{14}$ G, and for that reason are known as Magnetars. However, in the last years some SGRs/AXPs with low surface magnetic fields $B\sim(10^{12}-10^{13})$ G have been detected, challenging the Magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-Ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on white dwarfs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized white dwarfs can have surface magnetic field $B\sim 10^{7}-10^{10}$ G and rotate very fast with frequencies $\Omega\sim 1$ rad/s, consistent with the observed rotation periods $P\sim (2-12)$ s.