GRB 221028A: AGILE detection

The AGILE satellite detected the GRB 221028A at T0 = 2022-10-28 13:16:27 s (UTC), reported by Swift BAT (GCN #32874). 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 2 s and it released a total number of 3155 counts in the MCAL detector (above a background rate of 1180 Hz), and 7270 counts in the AC detector (above a background rate of 3410 Hz). The AGILE ratemeters light curves can be found at http://www.agilescienceapp.it/notices/GRB221028A_AGILE_RM.png . The event also triggered a high time resolution MCAL data acquisition, from T0-4.31 s to T0+33.35 s (UTC), and released 1924 counts in the detector, above a background rate of 477 Hz. The MCAL light curve can be found at http://www.agilescienceapp.it/notices/GRB221028A_080686_594047787.000000.png . The time-integrated spectrum of the burst between T0-2s and T0+7s be fitted in the energy range 0.4-10 MeV with a power-law with ph. ind. = -2.65 (-0.39/+0.50), resulting in a reduced chi-squared of 0.78 (48 d.o.f.) and a fluence of 3.1e-06 ergs/cm^2 (90% confidence level), in the same energy range. At the T0, the event was 49 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.