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GCN Circular 33655

Subject
GRB 230402A: Fermi GBM detection
Date
2023-04-19T17:35:11Z (8 months ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
C. Malacaria (ISSI) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 07:32:35.96 UT on 02 April 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230402A (trigger 702113560 / 230402314, GCN 33553),
which was also detected by AGILE (GCN 33555), AstroSat CZTI (GCN 33562),
CALET (GCN 33563) and Fermi-LAT (GCN 33650).
The Fermi GBM Final Real-time Localization (GCN 33553) is consistent
with the Fermi-LAT position.

The angle from the Fermi LAT boresight is 24 degrees.

The GBM light curve consists of a main peak
with a duration (T90) of about 63 s (50-300 keV).
The time-averaged spectrum from T0 s to T0+46 s is best fit by
a power law function with an exponential high-energy cutoff.  
The power law index is -0.94 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 1030 +/- 81 keV.

A Band function fits the spectrum equally well with 
Epeak= 995 +/- 85 keV, alpha = -0.93 +/- 0.02 and beta = -2.9 +/- 0.5 .

The event fluence (10-1000 keV) in this time interval is
(3.99 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.3 s in the 10-1000 keV band
is 10.7 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
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