TITLE:   GCN CIRCULAR
NUMBER:  34720
SUBJECT: GRB 230911A: Fermi GBM Observation
DATE:    23/09/17 00:27:58 GMT
FROM:    Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>

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

"At 03:09:32.88 UT on 11 September 2023, the
Fermi Gamma-ray Burst Monitor (GBM) triggered and located
GRB 230911A (trigger 716094577/230911132), which was also
detected by Swift/XRT (P. D'Avanzo et al. 2023, GCN 34702)
and GOTO (S. Belkin et al. 2023, GCN 34681). The Fermi GBM
Final Real-time Localization reported in GCN 34652 is
consistent with the Swift-XRT and GOTO localizations.

The angle from the Fermi LAT boresight is 54 degrees.

The GBM light curve consists of a single peak with a
duration (T90) of about 36 s (50-300 keV). The time-averaged
spectrum from T0-4 to T0+30 s is best fit by a Band function
with Epeak= 98 +/- 21 keV, alpha = -1.1 +/- 0.1 and
beta = -2.0 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(6.2 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.0 s in the 10-1000 keV band is 3.7 +/- 0.2 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/"