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Spin down rate and inferred dipole magnetic field of the new soft gamma-ray repeater SGR 1833-0832

ATEL # 2550; P. Esposito (INAF-IASF Milano), G. L. Israel (INAF-O.A.Roma), M. Burgay (INAF-O.A.Cagliari), A. Possenti (INAF-O.A.Cagliari), D. Gotz (Irfu/SAp/CEA Saclay), N. Rea (CSIC-ICE Barcelona), S. Mereghetti (INAF-IASF Mi), A. Tiengo (INAF-IASF Mi), L. Stella (INAF-0.A.Roma), R. Turolla (U. Padua), S. Zane (MSSL/UCL) on behalf of a larger collaboration
on 13 Apr 2010; 12:23 UT
Password Certification: Paolo Esposito (

Subjects: X-ray, Pulsars, Soft Gamma-ray Repeaters
Referred to by ATEL #: 2553

We observed the new soft gamma-ray repeater SGR 1833-0832 with XMM-Newton on 2010 March 23 (for about 22 ks) and on 2010 April 02 (for about 21 ks). By merging these data sets with those collected since the discovery of the source (GCN #10526) with RossiXTE and Swift, we were able to refine the period measurement reported in ATEL #2494 (see also ATEL #2493), also including in the phase-coherent timing solution a first period derivative component.

According to our preliminary analysis the period and first period derivative of SGR 1833-0832 are: P= 7.565406(2) s and Pdot= 7.4(2) x 10^-12 s/s (1 sigma uncertainties; epoch 55274.0 MJD). Under the standard assumption that the neutron star slows down because of magnetic braking, we infer a dipole magnetic field of B = 2.4(3) x 10^14 G for a neutron star with radius of 10 km and mass of 1.4 solar masses, confirming the SGR as a new magnetar candidate.

We will monitor the source both with XMM-Newton and Swift until the end of the current observability window (about end of April 2010).

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R. E. Rutledge , Editor
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