TITLE:   GCN CIRCULAR
NUMBER:  32884
SUBJECT: GRB 221027A: AGILE detection
DATE:    22/10/29 08:43:17 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

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

The AGILE satellite detected the GRB 221027A at T0 = 2022-10-27 04:09:34 s
(UTC), reported by Fermi GBM (GCNs #32861, #32866) and Fermi LAT (GCN
#32862). The burst is clearly visible in the AGILE scientific ratemeters of
the MiniCALorimeter (MCAL; 0.4-100 MeV) and AntiCoincidence (AC; 50-200
keV) detectors. The event lasted about 10 s and it released a total number
of 11040 counts in the MCAL detector (above a background rate of 1180 Hz),
and 30890 counts in the AC detector (above a background rate of 3250 Hz).
The AGILE ratemeters light curves can be found at
http://www.agilescienceapp.it/notices/GRB221027A_AGILE_RM.png .

The event also triggered a high time resolution MCAL data acquisition, from
T0-22.42 s to T0+7.94 s (UTC), and released 5086 counts in the detector,
above a background rate of 472 Hz. The MCAL light curve can be found at
http://www.agilescienceapp.it/notices/GRB221027A_080667_593928574.000000.png
. The time-integrated spectrum of the burst between T0 and T0+3s be fitted
in the energy range 0.4-10 MeV with a power-law with ph. ind. = -2.31
(-0.69/+1.26), resulting in a reduced chi-squared of 1.44 (48 d.o.f.) and a
fluence of 1.8e-06 ergs/cm^2 (90% confidence level), in the same energy
range. At the T0, the event was 67 deg off-axis.

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.