Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 8166

SGR 0501+4516: Spin Down Rate and Inferred Dipole Magnetic Field
2008-09-02T16:00:32Z (16 years ago)
Chryssa Kouveliotou at MSFC <>
SGR 0501+4516: Spin Down Rate and Inferred Dipole Magnetic Field

Peter M. Woods (Dynetics), Ersin Gogus (Sabanci University), Chryssa
Kouveliotou (NASA/MSFC), report on behalf of a larger collaboration:

We continued monitoring the new Soft Gamma Repeater SGR 0501+4516
(Barthelmy et al. 2008, GCN # 8113, Palmer et al. 2008, ATel # 1678)
using our SGR ToO Program with RXTE. We acquired a total exposure of 40
ks in 13 RXTE pointings performed over a time span of ~7.5 days. The
time spacing between each pointing ranged between 0.1 - 0.9 d. We detect
numerous (between 1 to 50) short bursts in observations before 2008
August 28. We clearly detect the 5.76 s pulsations reported by Gogus et
al. 2008 (ATel # 1677) in the 2-10 keV PCA data. We employed a quadratic
spline fit to phase residuals and measured the spin period, P =
5.762067(2) s and the spin-down rate, Pdot = 1.5(5) x 10^-11 s/s. Note
that our spin period measurement is consistent with that reported by
Mangano et al. (2008, ATel # 1682). Assuming that the neutron star slows
down via magnetic dipole radiation, we infer a dipole magnetic field of
B = 3 x 10^14 G, confirming the new SGR as a new magnetar candidate.
Looking for U.S. government information and services? Visit