[vsnet-grb-info 11890] Fermi/GBM detection of a burst from the magnetar 1E 2259+5

[GCN Circulars]

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  <chryssa.kouveliotou at nasa.gov>

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.