Pulsars and magnetars

TL;DR

This paper reviews the nature of anomalous X-ray pulsars and soft gamma-ray repeaters as magnetars, highlighting their unique magnetic energy-powered emissions, observational properties, and recent discoveries of low-field magnetars.

Contribution

It provides a comprehensive review of magnetar properties, discusses recent low-field magnetar discoveries, and explores their relation to other neutron star classes.

Findings

AXPs/SGRs are powered by magnetic energy, not accretion or rotation.

Recent discovery of magnetars with low external dipole fields.

Connections between AXPs/SGRs and other neutron star types.

Abstract

The high-energy sources known as anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are well explained as magnetars: isolated neutron stars powered by their own magnetic energy. After explaining why it is generally believed that the traditional energy sources at work in other neutron stars (accretion, rotation, residual heat) cannot power the emission of AXPs/SGRs, I review the observational properties of the twenty AXPs/SGRs currently known and describe the main features of the magnetar model. In the last part of this review I discuss the recent discovery of magnetars with low external dipole field and some of the relations between AXPs/SGRs and other classes of isolated neutron stars.