[vsnet-grb-info 6907] SGR 1806-20: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8497
SUBJECT: SGR 1806-20: Fermi GBM detection 
DATE:    08/11/07 17:26:47 GMT
FROM:    Sheila McBreen at MPE  <smcbreen at mpe.mpg.de>

Sheila McBreen (UCD/MPE) and Chryssa Kouveliotou (NASA/MSFC)
report on behalf of the Fermi GBM Team:

"At 05:47:04.08 UT on 06 November 2008, the Fermi Gamma-Ray Burst Monitor
triggered on a soft, short event (trigger 247643225 / 081106241).

The on-ground calculated location, using the GBM trigger
data, is RA = 271.3, DEC = -16.2 (J2000 degrees,
equivalent to 18 h 05 m, -16 d 12 '), with an uncertainty
of 5.6 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error for soft localisations which is currently estimated
to be 5 to 6 degrees). This position is consistent with SGR 1806-20.
The angle from the Fermi LAT boresight is 41 degrees.

The GBM light curve comprises a single peak with a duration of about 80 ms.
The time-averaged spectrum from T0-0.045 s to T0+0.035 s is
adequately fit by a simple power law function with index -2.13 +/- 0.08.
(chi squared 205.1, for 242 d.o.f.) The event fluence (10-100 keV)
in this time interval is (7.9 +/- 0.3)E-8 erg/cm^2.

An optically thin thermal bremsstrahlung (OTTB) function
fits the spectrum equally well (chi squared 203.9 for 242 d.o.f.)
with kT = 36.5 +/-3.9 keV.

The spectral analysis results presented above are preliminary,
Final results will be published in the GBM Magnetar catalog."