TITLE:   GCN CIRCULAR
NUMBER:  34391
SUBJECT: GRB 230812B: Fermi GBM Observation of a very bright burst
DATE:    23/08/13 01:41:45 GMT
FROM:    Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>

O.J. Roberts (USRA), C. Meegan (UAH), S. Lesage (UAH), E. Burns (LSU), and S. Dalessi (UAH) 
report on behalf of the Fermi GBM Team:

"At 18:58:12.05 UT on 12 August 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230812B (trigger 713559497 / 230812790). The Fermi 
GBM Final Real-time Localization was previously reported (GBM team 2023, GCN 34386). 

The angle from the Fermi LAT boresight at the GBM trigger time is 29 degrees.

The GBM light curve consists of a FRED-like burst with a duration (T90)
of about 3 s (10-1000 keV). The time-averaged spectrum over the whole burst
from T0-1s to T0+32 s is best fit by a Band function with Epeak = 273 +/- 3 keV,  
alpha of -0.80 +/- 0.01 and beta of -2.47 +/-0.02.

The event fluence (10-1000 keV) in this time interval is
(2.5201 +/- 0.0002)E-04 erg/cm^2. The 1s peak photon flux measured
starting from T0+0.6 s in the 10-1000 keV band is 740 +/- 2 ph/s/cm^2.

Due to a timing glitch in the middle of the burst in the TTE data, this data
type had to be reprocessed and consequently, this preliminary report used the 
CSPEC and CTIME data types only, which were unaffected. We note that due
to the intensity of the burst, pulse pile-up during the burst is highly likely.
This analysis is ongoing. 

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/"