TITLE:   GCN CIRCULAR
NUMBER:  8775
SUBJECT: GRB 081229: Fermi GBM detection
DATE:    09/01/03 10:00:27 GMT
FROM:    Sheila McBreen at MPE  <smcbreen@mpe.mpg.de>

Sheila McBreen (UCD/MPE) and Elisabetta Bissaldi (MPE)
report on behalf of the Fermi GBM Team:

"At 04:29:01.88 UT on 29 January 2008, the Fermi Gamma-Ray Burst Monitor
triggered and located a short burst GRB 081229 (trigger 252217742 /
081229187).

The on-ground calculated location, using the GBM trigger
data, is RA = 170.5, DEC = 55.1 (J2000 degrees,
equivalent to 11 h 22 m, 55 d 06 '), with an uncertainty
of 8 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 44 degrees.

The GBM light curve consists of one pulse
with a duration of about 0.5 s (8-1000 keV).
The time-averaged spectrum from T0-0.106 s to T0+0.214 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.42 +/- 0.18 and
the cutoff energy, parameterized as Epeak, is 807 +/- 186 keV
(chi squared 437 for 485 d.o.f.).

A Band function fits the spectrum equally well with
Epeak = 585  +/- 188 keV, alpha=-0.27 +/- 0.27
and beta = -2.0 +/- 0.3 (chi squared 429 for 484 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(8.7 +/- 0.8)E-7 erg/cm^2. The 64-ms peak photon flux measured
starting from T0-0.042 s  using the Band model in the 8-1000 keV band
is 10.7 +/- 1.5 ph/s/cm^2.

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