TITLE: GCN CIRCULAR NUMBER: 13280 SUBJECT: Fermi/GBM detection of a burst from the magnetar 1E 2259+5 DATE: 12/05/04 17:51:15 GMT FROM: Chryssa Kouveliotou at MSFC S. Foley (UCD), C. Kouveliotou (NASA/MSFC), Y. Kaneko (Sabanci University) and Andrew Collazzi (NASA/ORAU) report on behalf of the Fermi/GBM Team:   At 08:17:43.71 UT on 21 April 2012, the Fermi Gamma-Ray Burst Monitor triggered on a short, soft event very similar to an SGR burst (trigger 356689065/120421346).   The on-ground calculated location is RA = 357.0, DEC = 40.0(J2000 degrees, equivalent to 23h 48 m, 40d 00'), with an uncertainty of 12 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). This location is consistent with 1E 2259+586, albeit with a large error radius.   The event had a duration of ~ 40 ms (20-100 keV) and was equally well fit either with an OTTB function of kT=85+-17 keV or with a single blackbody spectrum of kT=17+-1 keV. These results are preliminary.   Untriggered event searches between April 18-24, 2012 (+- 3 days around the trigger time) did not reveal any additional bursts at the same significance level from the same direction.   Given the recent report by Archibald et al. (ATel 4080, 2012) about the detection of a flux increase of 1E 2259+586 with Swift, we suggest that this magnetar source was indeed the origin of the GBM burst.   Further observations of the source in multiple wavelengths are encouraged.