TITLE:   GCN CIRCULAR
NUMBER:  33440
SUBJECT: GRB 230308A: Fermi GBM detection
DATE:    23/03/09 15:35:20 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts@nasa.gov>

C. Malacaria (ISSI) reports on behalf of the Fermi GBM Team:

"At 13:32:27.40 UT on 8 March 2023, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 230308A (trigger 699975152 / 230308564).
The Fermi GBM Final Real-time Localization was reported in GCN 33420.

The angle from the Fermi LAT boresight at the GBM trigger time is 42 degrees.

The GBM light curve consists of a slightly structured main peak
with a duration (T90) of about 0.6 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.64 s
is best fit by a power law function with an exponential high-energy cutoff.
The power law index is -0.52 +/- 0.03 and the cutoff energy,
parameterized as Epeak, is 943 +/- 46 keV.

A Band function fits the spectrum equally well
with Epeak= 907 +/- 52 keV, alpha = -0.51 +/- 0.03,
beta = -3.1 +/- 0.4 .

The event fluence (10-1000 keV) in this time interval is
(8.5 +/- 0.2)E-06  erg/cm^2. The 0.064-sec peak photon flux measured
starting from T0 in the 10-1000 keV band
is 72 +/- 2 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/"