TITLE:   GCN CIRCULAR
NUMBER:  37436
SUBJECT: GRB 240905B: Fermi GBM Observation
DATE:    24/09/09 16:29:13 GMT
FROM:    Sarah Dalessi at UAH <sd0104@uah.edu>

S. Dalessi (UAH), A. Myers (NPP/GSFC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 04:27:16.14 UT on 05 September 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240905B (trigger 747203241/240905186).
which was also detected by AstroSat (J. Joshi et al. 2024, GCN 37391) and Fermi-LAT (R. Gupta et al. 2024, GCN 37418).
The Fermi GBM on-ground location is consistent with the AstroSat and Fermi-LAT positions.

The angle from the Fermi LAT boresight is 25 degrees.

The GBM light curve single emission episode with a duration (T90)
of about 1.3 s (50-300 keV). The time-averaged spectrum
from T0+0 to T0+1.280 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.36 +/- 0.04 and the cutoff energy,
parameterized as Epeak, is 1240 +/- 70 keV.

The event fluence (10-1000 keV) in this time interval is
(5.11 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.32 s in the 10-1000 keV band is 30 +/- 1 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 1223 +/- 70 keV, alpha = -0.36 +/- 0.04 and beta = -4.16 +/- 1.24.


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/"