A low-magnetic-field Soft Gamma Repeater
Rea, N ; Esposito, P ; Turolla, R ; et al. ; - ASI Sponsor
Nov - 2010
ISSN : 1095-9203 ;
journal : Science

Issue : 6006
type: Article Journal

Abstract
Soft gamma repeaters (SGRs) and anomalous x-ray pulsars form a rapidly increasing group of x-ray sources exhibiting sporadic emission of short bursts. They are believed to be magnetars, that is, neutron stars powered by extreme magnetic fields, B 10(14) to 10(15) gauss. We report on a soft gamma repeater with low magnetic field, SGR 0418+5729, recently detected after it emitted bursts similar to those of magnetars. X-ray observations show that its dipolar magnetic field cannot be greater than 7.5 × 10(12) gauss, well in the range of ordinary radio pulsars, implying that a high surface dipolar magnetic field is not necessarily required for magnetar-like activity. The magnetar population may thus include objects with a wider range of B-field strengths, ages, and evolutionary stages than observed so far.

keywords : ASI - Sponsor