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GCN Circular 9844

Subject
GRB 090828: Fermi GBM detection
Date
2009-08-28T17:12:22Z (15 years ago)
From
Sheila McBreen at MPE <smcbreen@mpe.mpg.de>
S. McBreen (UCD/MPE)
reports on behalf of the Fermi GBM Team:

"At 02:22:48.20  UT on 28 August 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090828 (trigger 273118970 / 090828099 ).

The on-ground calculated location, using the GBM trigger
data, is RA = 124.4, DEC = -26.1 (J2000 degrees,
equivalent to 08 h 18 m, -26 d 06 '), with an uncertainty
of 1.2 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 95 degrees.
This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of three pulses
with a duration (T90) of about 100 s (8-1000 keV).
The time-averaged spectrum from T0-0 s to T0+103 s is
well  fit by
a Band function with Epeak = 136.5 (+16.0/-13.7) keV,
alpha = -1.23 (+0.06/-0.05), and beta = -2.12 (+0.08/-0.11)
(chi squared 549 for 485 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(2.52 +/- 0.08)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+52.2 s in the 8-1000 keV band
is 16.2 +/- 0.5 ph/s/cm^2.

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