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GCN Circular 8803

Subject
GRB 090112: Fermi GBM detection
Date
2009-01-13T16:44:12Z (15 years ago)
From
Elisabetta Bissaldi at MPE <ebs@mpe.mpg.de>
E. Bissaldi (MPE) and A. von Kienlin (MPE)
report on behalf of the Fermi GBM Team: 


"At 07:57:23.11 UT on 12 January 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090112 (trigger 253439845 / 090112332).
The on-ground calculated location, using the GBM trigger
data, is RA = 111.8, DEC = -30.3 (J2000 degrees,
equivalent to 07h 27m, -30d 17'), with an uncertainty
of 1.7 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 4 degrees.

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

The GRB lightcurve consists of two peaks with some substructure
appearing at T0 and T0+4 s, respectively. A possible precursor
is present around T0-20 s and additional weak emission is visible
up to T0+50s. The event duration (T90) is about 65 s (8-1000 keV)
and T50 is about 27 s (8-1000 keV).
The time-averaged spectrum from T0-6 s to T0+18 s is
best fit by a Band function with Epeak =  150 +/- 40 keV,
alpha = -0.94 +/- 0.20 and beta = -2.01 +/- 0.19
(chi squared 464 for 456 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(5.2 +/- 1.0)E-06 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+4 s in the 8-1000 keV band 
is 7 +/- 2 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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