X-ray emission from neutron stars with supercritical magnetic fields: A model for the soft gamma repeaters

Abstract

A magnetar is defined to be a neutron star with a supercritical magnetic dipole field: Bdipole≳Bcr≡m2e/e=4.4× 1013 G. (We use units in which ℏ=c=kB=1). We have suggested that a neutron star born with a very short spin period, P≊1–3 ms is the site of an effective dynamo that can generate fields of this strength. Some peculiar properties of the 1979 March 5 burst and its repeat bursts point to these objects as the source of the soft gamma repeaters (SGRs). Young magnetars release an enormous amount of energy as they spin down via magnetic torques, and are a possible sources of cosmological gamma‐ray bursts. Here we outline some results on the thermal and magnetic evolution of magnetars, and discuss various applications to the SGRs and to the X‐ray pulsar 1E2259+586.