Wind braking of magnetars

TL;DR

This paper proposes a wind braking model for magnetars, explaining recent observational challenges by suggesting that particle winds influence magnetic field measurements and magnetar behavior, with specific predictions for pulsar wind nebulae and braking indices.

Contribution

It introduces a wind braking scenario for magnetars, emphasizing the role of particle winds and multipole magnetic fields, offering explanations for various observational phenomena and predicting new features.

Findings

Magnetars may have strong multipole fields with weak dipole components.

The wind braking model explains normal supernova energies and non-detections in Fermi observations.

Predicted phenomena include magnetism-powered pulsar wind nebulae and braking indices less than three.

Abstract

(adapted)Considering recent observations challenging the traditional magnetar model, we explore the wind braking of magnetars. There is evidence for strong multipole magnetic fields in active magnetars, but the dipole field inferred from spin down measurements may be strongly biased by a particle wind. Recent challenging observations of magnetars may be explained naturally in the wind braking scenario: (1) The supernova energies of magnetars are of normal value; (2) The non-detection in Fermi observations of magnetars; (3) The problem posed by the low-magnetic field soft gamma-ray repeaters; (4) The relation between magnetars and high magnetic field pulsars; (5) A decreasing period derivative during magnetar outbursts. Transient magnetars may still be magnetic dipole braking. This may explain why low luminosity magnetars are more likely to have radio emissions. In the wind braking scenario, magnetars are neutron stars with strong multipole field. For some sources, a strong dipole field may be no longer needed. A magnetism-powered pulsar wind nebula and a braking index smaller than three are the two predictions of the wind braking model.