[vsnet-grb-info 11562] Fermi GBM detection of an SGR-like burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12958
SUBJECT: Fermi GBM detection of an SGR-like burst
DATE:    12/02/15 10:19:00 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:

"At 09:07:49.67 UT on 07 February 2012, the Fermi Gamma-Ray Burst Monitor
triggered on a soft, short event (trigger 350298471 / 120207380). The event
was tentatively classified as a solar flare, but it may be a burst from a
Galactic source, most likely the soft gamma repeater SGR 1806-20.

The on-ground calculated location, using the GBM trigger data, is RA =
270.0, DEC = -24.5 (J2000 degrees, equivalent to 18 h 00 m, -24 d 30 '),
with an uncertainty of 3.9 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 corresponds to Galactic coordinates:
Long = 8.9, Lat = -6.9   (J2000 degrees), consistent with the position of
SGR 1806-20 and other known SGRs in that region. We conclude that this burst
is either coming from one of these sources or from a new, yet unknown
source.

The angle from the Fermi LAT boresight is 80 degrees.

The GBM light curve shows a single peak with a duration of about 150 ms. The
time-averaged spectrum from T0-0.032 s to T0+0.096s is best fit by a power
law function with an exponential high-energy cutoff. The power law index is
-0.04 +/- 0.31 and the cutoff energy, parameterized as Epeak, is 25.5 +/-
1.2 keV.
The event fluence (10-1000 keV) in this time interval is (1.9 +/- 0.1)E-07
erg/cm2.

The temporal and spectral analysis results presented above are preliminary."