[vsnet-grb-info 8333] GRB 090829B: Fermi GBM Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9856
SUBJECT: GRB 090829B: Fermi GBM Detection
DATE:    09/09/01 02:58:06 GMT
FROM:    Colleen A. Wilson at NASA/MSFC/NSSTC  <colleen.wilson at nasa.gov>

Colleen A. Wilson-Hodge (NASA/MSFC)reports on behalf of the Fermi GBM Team:

"At 16:50:40.13 UT on 29 August 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090829B (trigger 273257442 / 090829702).

The on-ground calculated location, using the GBM trigger data, is
RA = 355.0, DEC = -9.4 (J2000 degrees, equivalent to 23 h 40 m, -9 d 22'),
with an uncertainty of 3.2 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 42 degrees.

The GBM light curve consists of two widely spaced peaks with a duration
(T90) of about 100 s (8-1000 keV). The time-averaged spectrum from
T0-1.5 s to T0+31.2 s is best fit by a Band function with
Epeak = 143 +/- 30 keV, alpha = -0.7 +/- 0.2, and beta = -2.4 +/- 0.5

The event fluence (8-1000 keV) in this time interval is
(6.4 +/- 0.7)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.6 s in the 8-1000 keV band is 3.2 +/- 0.3 ph/s/cm^2.

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