TITLE:   GCN CIRCULAR
NUMBER:  33583
SUBJECT: GRB 230405B: Fermi GBM Observation
DATE:    23/04/06 21:06:17 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 19:58:03 UT on 05 April 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230405B (trigger 702417488/230405832).
which was also detected by the Swift/BAT and Swift/XRT (K. L. Page et al. 2023, GCN 33571).
The Fermi GBM on-ground location is consistent with the Swift XRT position.

The angle from the Fermi LAT boresight is 105 degrees.

The GBM light curve consists of a single pulse with a duration (T90)
of about 4.3 s (50-300 keV). The time-averaged spectrum
from T0+0.0 to T0+5.1 s is best fit by
a Band function with Epeak = 225 +/- 11 keV,
alpha = -0.53 +/- 0.05, and beta = -2.4 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(1.2 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.5 s in the 10-1000 keV band is 27.5 +/- 0.5 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/"