[vsnet-grb-info 7356] GRB 090227B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8921
SUBJECT: GRB 090227B: Fermi GBM detection
DATE:    09/03/01 08:49:18 GMT
FROM:    Sylvain Guiriec at UAH  <sylvain.guiriec at lpta.in2p3.fr>

S. Guiriec (UAH)
reports on behalf of the Fermi GBM Team:

"At 18:31:01.41 UT on 27 February 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located the short and bright GRB 090227B
(trigger 257452263 / 090227772).

The on-ground calculated location, using the GBM trigger data, is
RA = 11.81, Dec = +32.17 (J2000 degrees, equivalent to 11h48m36,+32d10'12),
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 72 degrees.

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

The GBM light curve consists of one spike with a duration (T90) of about
0.9 s (10-1000 keV).
The time-averaged spectrum from T0-0.1s to T0+0.4s is best fitted by a Band
function with Epeak = 2255 +/- 116 keV,  alpha = -0.53 +/- 0.02, and
beta = -3.04 +/- 0.23 (chi squared 673 for 607 d.o.f.).

The event fluence (10-1000 keV) in this time interval is
(0.87 +/- 0.01)E-05 erg/cm^2. The 1-sec peak photon flux measured starting
from T0 in the 10-1000 keV band is 34.6 +/- 0.3 ph/s/cm^2.

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