SGR 0418+5729: a low-magnetic-field magnetar
  Soft gamma-ray repeaters and anomalous X-ray pulsars are a small (but growing) group of X-ray sources characterized by the emission of short bursts and by a large variability in their persistent flux. They are believed to be magnetars, i.e. neutron stars powered by extreme magnetic fields 1E14-1E15 G). We found evidence for a magnetar with a low magnetic field, SGR 0418+5729, recently detected after it emitted bursts similar to those of soft gamma-ray repeaters. New X-ray observations show that its dipolar magnetic field cannot be greater than 8E12 G, 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 magnetic-field strengths, ages and evolutionary stages than observed so far. 
P. Esposito, N. Rea, R. Turolla, G. L. Israel, S. Zane, L. Stella, C.   Kouveliotou, S. Mereghetti, A. Tiengo, D. Gotz, E. Gogus
astro-ph.HE