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GCN Circular 31726

Subject
GRB 220308B: Fermi GBM detection
Date
2022-03-10T01:57:07Z (2 years ago)
From
Cori Fletcher at USRA <cfletcher@usra.edu>
C. Fletcher (USRA), O. J. Roberts (USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 05:35:30.10 UT on 08 March 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220308B (trigger 668410535 / 220308233).

The on-ground calculated location, using the GBM trigger
data, is RA = 292, DEC = 26 (J2000 degrees,
equivalent to 19 h 27 m, 26 d 26'), with a statistical uncertainty
of 5 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 78 degrees.

The GBM light curve consists of multiple peaks
with a duration (T90) of about 33 s (50-300 keV).
The time-averaged spectrum from T0+0.003 s to T0+32.769 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.0 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 342 +/- 93 keV,

The event fluence (10-1000 keV) in this time interval is
(4.4 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.512 s in the 10-1000 keV band
is 1.9 +/- 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/"
FSSC: Data � Data Access � GBM - Fermi Gamma-ray Space Telescope<https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/>
ID Name Description; GS-001: CTIME (daily version) The counts accumulated every 0.256 seconds in 8 energy channels for each of the 14 detectors. GS-002
fermi.gsfc.nasa.gov
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