TITLE:   GCN CIRCULAR
NUMBER:  8720
SUBJECT: GRB 081223: Fermi GBM detection
DATE:    08/12/24 12:33:20 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs@mpe.mpg.de>

Elisabetta Bissaldi (MPE)
reports on behalf of the Fermi GBM Team: 


"At 10:03:57.15 UT on 23 December 2008, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 081223 (trigger 251719438 / 081223419).
The on-ground calculated location, using the GBM trigger
data, is RA = 116.7, Dec = 33.5 (J2000 degrees,
equivalent to 07h 47m, 33d 30'), with an uncertainty
of 6.2 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).

The angle from the Fermi LAT boresight is 28 degrees.

This short burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of a single spike
with a duration (T90) of about 890 ms (8-1000 keV).
The time-averaged spectrum from T0-0.078 s to T0+0.434 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.63 +/- 0.10 and
the cutoff energy, parameterized as Epeak, is 280 +/- 30 keV
(chi squared 334 for 318 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(1.20 +/- 0.10)E-06 erg/cm^2. The 64-ms peak photon flux
measured starting from T0+0.114 s in the 
8-1000 keV band is 22 +/- 3 ph/s/cm^2.


The spectral analysis results presented above are preliminary; 
final results will be published in the GBM GRB Catalog."