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GCN Circular 33715

Subject
GRB 230430A: Fermi GBM observation
Date
2023-05-02T07:00:05Z (a year ago)
From
Joe Mangan at IJCLab <joseph.mangan@ijclab.in2p3.fr>
J.Mangan (CNRS/IJCLab) and C. Meegan (UAH) report on behalf of the Fermi-GBM Team:

"At 07:47:18.81 UT on 30 April 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230430A (trigger 704533643 / 230430325), which was also detected by AstroSat CZTI (P K. Navaneeth et al. 2023, GCN 33714). The Fermi GBM Final Real-time Localization is reported in GCN 33713.

The angle from the Fermi LAT boresight at the GBM trigger time is 22 degrees.

The GBM light curve consists of a single emission
with a duration (T90) of about 0.32 s (50-300 keV).
The time-averaged spectrum from T0-0.19 s to T0+0.45 s is best fit by
a power law function with an exponential
high-energy cutoff.  The power law index is -0.6 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 528.4 +/- 58.1 keV. A Band function fits the spectrum equally well with Epeak= 363.8 +/- 57.2 keV, alpha = -0.4 +/- 0.1 and beta = -2.2 +/- 0.3.

The event fluence (10-1000 keV) in this time interval is
(1.7 +/- 0.1)E-6 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+-0.13 s in the 10-1000 keV band
is 25.9 +/- 1.5 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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