TITLE:   GCN CIRCULAR
NUMBER:  23551
SUBJECT: GRB 181222B : Fermi GBM detection
DATE:    18/12/23 05:35:51 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P Veres (UAH) reports on behalf of the Fermi GBM Team:

"At 20:11:37.438 UT on 22 December 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 181222B (trigger 567202302 / 181222841).

The on-ground calculated location, using the GBM trigger
data, is RA = 311.2, DEC = 22.9 (J2000 degrees,
equivalent to 22 h 45 m, 22 d 52 '), with an uncertainty
of 1.6 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 65
degrees.


The GBM light curve shows a very intense peak
with a duration (T90) of about 0.5 s (50-300 keV).
The time-averaged spectrum from T0  to T0+1.1 s is best fit by
a Band function with Epeak = 380 +/- 8 keV,
alpha = -0.74 +/- 0.01, and beta = -2.98 +/- 0.11

The event fluence (10-1000 keV) in this time interval is
(3.44 +/- 0.03)E-5 erg/cm^2. The 64 ms peak photon flux measured
starting from T0+0.14 s in the 10-1000 keV band
is 800 +/- 6 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."