Swift/XMM-Newton refined timing solution for SGR0501+4516

ATel #1692; G. L. Israel (INAF/OA Roma), N. Rea (U. Amsterdam), V. Mangano (INAF/IASF Pa), P. Esposito, A. Tiengo, S. Mereghetti (INAF/IASF, Milan), D. Gotz (CEA/Saclay), S. Zane (UCL/MSSL), J. Kennea (PSU), M. Perri (ASDC), G. Cusumano (INAF-IASF PA), D. N. Burrows (PSU), N. Gehrels (GSFC), D. Palmer (LANL), S. Barthelmy (GSFC) report on behalf of a larger collaboration
on 3 Sep 2008; 14:19 UT
Credential Certification: GianLuca Israel (gianluca@mporzio.astro.it)

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The Swift satellite observed SGR 0501+4516 several times during the last two weeks (ATEL #1676, #1677, #1678, #1682, #1683), and XMM-Newton observed the source on August 23rd (ATEL #1688). By merging the two datasets we were able to obtain a phase-coherent timing solution.

According to our analysis the preliminary period and period derivative of SGR 0501+4516 are: P = 5.7620699(4) s and Pdot = 5(1) x ×10^-12 s/s (1 sigma uncertainties). Both values are consistent and have smaller uncertainties than those reported so far (ATEL #1691; where P = 5.762067(2) s and Pdot = 1.5(5) x ×10^-11 s/s).

With these refined values we infer a magnetic field strength of the dipolar component of approximately (assuming a neutron star radius of 10 km and a mass of 1.4 solar masses) Bd = 1.7 x ×10¹⁴ Gauss, similar to other magnetars.

Further Swift and XMM observations have been performed and/or planned and will allow to increase the accuracy of the above reported phase-coherent timing solution.