[vsnet-grb-info 7363] GRB 090228B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8927
SUBJECT: GRB 090228B: Fermi GBM detection
DATE:    09/03/03 23:31:08 GMT
FROM:    Vandiver Chaplin at UAH/Fermi-GBM  <chapliv at email.uah.edu>

V.Chaplin (UAH) reports on behalf of the Fermi GBM Team:

"At 23:25:01.02 UT on 28 FEB 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090228B (trigger 257556303 / 090228976).

The on-ground calculated location, using the GBM trigger
data, is RA = 356.5, DEC = +36.1 (J2000 degrees,
equivalent to 23h 44m, +36d 10' ), with an uncertainty
of 1.77 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 20 degrees.

The GBM light curve consists of one main pulse
with a duration (T90) of about 7.232 s (8-1000 keV).
The time-averaged spectrum from T0-1.408 s to T0+5.760 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.6963 +/- 0.293 and
the cutoff energy, parameterized as Epeak, is 147.8 +/- 34.1 keV
(chi squared 221.01 for 235 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(9.9607 +/- 0.22)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.688 s in the 8-1000 keV band
is 2.53 +/- 1.0 ph/s/cm^2.


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