TITLE: GCN CIRCULAR NUMBER: 31309 SUBJECT: GRB 211226A: AGILE/MCAL detection of a burst DATE: 21/12/26 12:10:53 GMT FROM: Alessandro Ursi at INAF/IAPS A. Ursi (INAF/IAPS), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), F. Longo (Univ. Trieste and INFN Trieste), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y. Evangelista, L. Foffano, E. Menegoni, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team: The AGILE Mini-CALorimeter (MCAL) detected a long burst at T0 = 2021-12-26 05:25:41.00 +/- 0.01 s (UTC) (INTEGRAL SPI-ACS trigger Tri,Sub: 9576,0). The event lasted about 20 s and released a total number of 2736 counts in the detector (in the 0.4-100 MeV energy range), above an average background rate of 613 Hz. The MCAL light curve shows several peaks and can be found at http://www.agilescienceapp.it/notices/GRB211226A_AGILE_MCAL.png . 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 released a total number of 492 counts in the SA detector (above a background rate of 115 Hz), 5996 counts in the MCAL detector (above a background rate of 1290 Hz), and 16770 counts in the AC detector (above a background rate of 3530 Hz). The AGILE ratemeter light curves can be found at http://www.agilescienceapp.it/notices/GRB211226A_AGILE_RM.png . The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the energy range 0.4-100 MeV. 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.