TITLE: GCN CIRCULAR NUMBER: 32479 SUBJECT: GRB 220823A: Fermi GBM detection DATE: 22/08/24 16:43:38 GMT FROM: Boyan A. Hristov at UAH bah0046@uah.edu
B. Hirstov (UAH) and C. Fletcher (USRA) report on behalf of the Fermi GBM Team:
"At 03:28:52.39 UT on 23 August 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220823A (trigger 682918137 / 220823145),which was also detected by Swift/BAT-GUANO (A. Tohuvavohu et al. 2022, GCN 32476).
The on-ground calculated location, using the GBM trigger data, is RA = 82.94, DEC = +2.44 (J2000 degrees, equivalent to 05h, 31m, 2d 26'), with a statistical uncertainty of 3 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The angle from the Fermi LAT boresight at the GBM trigger time is 15 degrees.
The GBM light curve consists of single peak with a duration (T90) of 1.1 +/- 0.7 s (50-300 keV).
The time-averaged spectrum from T0-1.024 s to T0+0.256 s is best fit by a power law with an exponential cutoff with Epeak = 1189 +/- 608 keV and alpha = -0.52 +/- 0.26.
The event fluence (10-1000 keV) in this time interval is (1.1 +/- 0.1)E-6 erg/cm^2. The 0.064-sec peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 5 +/- 1 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/"