A low-magnetic-field soft gamma repeater

N. Rea (1) , P. Esposito (2) , R. Turolla (3, 4) , G. L. Israel (5) , S. Zane (4) , L. Stella (5) , S. Mereghetti (5) , A. Tiengo (5) , D. Götz (6) , E. Göğüş (7) , C. Kouveliotou (8)

1 ICE-CSIC - Institut de Ciencies de l'Espai [Barcelona]
2 IASF-MI - Istituto di Astrofisica Spaziale e Fisica Cosmica - Milano
3 Unipd - Università degli Studi di Padova = University of Padua
4 MSSL - Mullard Space Science Laboratory
5 INAF - Istituto Nazionale di Astrofisica
6 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
7 Sabanci University [Istanbul]
8 MSFC - NASA Marshall Space Flight Center

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.

Domains: Astrophysics [astro-ph]

N. Rea, P. Esposito, R. Turolla, G. L. Israel, S. Zane, et al.. A low-magnetic-field soft gamma repeater. Science, 2010, 330 (6006), pp.944-946. ⟨10.1126/science.1196088⟩. ⟨cea-00862606⟩