Origin of magnetar-scale crustal field in PSR J1852+0040 and "frozen" magnetars

TL;DR

This paper investigates the origin of strong crustal magnetic fields in the neutron star PSR J1852+0040, challenging the dynamo mechanism hypothesis and discussing implications for magnetar formation theories.

Contribution

It provides evidence against the dynamo origin of magnetic fields in certain neutron stars and explores the implications for magnetar formation scenarios.

Findings

The neutron star's long spin period suggests a non-dynamo magnetic field origin.

Submerged magnetic fields in some CCOs could account for magnetar-like properties.

The fraction of magnetars with submerged fields may be only a few percent.

Abstract

We discuss the origin of strong crustal magnetic field in one of central compact objects (CCOs) --- a neutron star PSR J1852+0040 in the supernova remnant Kes 79. Taking into account its relatively long present day spin period we conclude that the field could not be generated via a dynamo mechanism. If this neutron star indeed is a magnetar with field submerged during a strong fall-back episode, then it argues against the dynamo field origin in magnetars. Otherwise, Kes 79 is not a close relative of normal magnetars. A discovery of an anti-magnetar with a millisecond period and strong crustal field identifiable, for example, due to large pulse fraction, would be the proof of the dynamo field origin. Existence of such sources is in correspondence with the present standard picture of neutron star unification. However, the fraction of magnetars with submerged fields can be small --- few percent of the total number of CCOs.