TITLE:   GCN CIRCULAR
NUMBER:  31105
SUBJECT: GRB 211120A: AGILE detection
DATE:    21/11/23 15:05:36 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), C. Pittori (SSDC, and INAF/OAR), A. Trois
(INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A.
Argan, M. Cardillo, C. Casentini, Y. Evangelista, E. Menegoni, L. Foffano,
G. Piano (INAF/IAPS), F. Lucarelli, F. Verrecchia (SSDC, and INAF/OAR), A.
Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N. Parmiggiani
(INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University),
M. Pilia (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste
and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of the
AGILE Team:

The AGILE satellite detected the GRB 211120A at T0 = 2021-11-20 23:05:20
(UTC), reported by GECAM (GCN #31100) and AstroSat CZTI (GCN #31104).

The burst is clearly visible in the AGILE scientific ratemeters of the
SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and
AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 6 s and
it released a total number of 821 counts in the SA detector (above a
background rate of 96 Hz), 9275 counts in the MCAL detector (above a
background rate of 1210 Hz), and 23969 counts in the AC detector (above a
background rate of 3440 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB211120A_AGILE_RM.png .

The event also triggered a partial high time resolution MCAL data
acquisition, covering the main peak of the burst, from T1 = 2021-11-20
23:05:20.0 s +/- 0.5 (UTC) to T2 = 2021-11-20 23:05:26.0 +/- 0.5 s (UTC),
and released 2291 counts in the detector, above a background rate of 710
Hz. The time-integrated spectrum of the burst between T1 and T1+2.43 s can
be fitted in the energy range 0.4-20 MeV with a single power-law with ph.
ind. = -2.43 (-0.34/+0.44), resulting in a reduced chi-squared of 1.09 (62
d.o.f.) and a fluence of 5.9e-06 ergs/cm^2 (90% confidence level), in the
same energy range. The MCAL light curve can be found at:
http://www.agilescienceapp.it/notices/GRB211120A_MCAL.png .

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html. Please
note that in the MCAL notice #564534599 the T0 was affected by a temporal
shift of about +279 sec due to a temporary ground software problem now
solved.