TITLE:   GCN CIRCULAR
NUMBER:  31778
SUBJECT: GRB 220317A: Fermi GBM detection
DATE:    22/03/21 16:46:18 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007@uah.edu>

R. Hamburg (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 12:48:30.66 UT on 17 March 2022, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 220317A (trigger 669214115 / 220317534).
which was also detected by the Swift/BAT-GUANO (Tohuvavohu et al. 2022, GCN
31766).

The angle from the Fermi LAT boresight at the GBM trigger time is 48
degrees.

The GBM light curve shows two peaks with a duration (T90)
of about 14 s (50-300 keV). The time-averaged spectrum
from T0-6.1 s to T0+8.2 s is best fit by a power law
function with an exponential high-energy cutoff.
The power law index is -1.1 +/- 0.2 and the cutoff
energy, parameterized as Epeak, is 248 +/- 96 keV.

The event fluence (10-1000 keV) in this time interval is
(1.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.4 s in the 10-1000 keV band
is 1.6 +/- 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/"