TITLE: GCN CIRCULAR NUMBER: 31344 SUBJECT: GRB 211229B: AGILE detection DATE: 21/12/31 14:35:32 GMT FROM: Alessandro Ursi at INAF/IAPS alessandro.ursi@gmail.com
A. Ursi (INAF/IAPS), C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), 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 (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, A. Trois (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 long GRB 211229B at T0 = 2021-12-29 22:18:43 (UTC), reported by Fermi GBM (GCN #31336) and GECAM (GCN #31339).
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 40 s and it released a total number of 5440 counts in the SA detector (above a background rate of 120 Hz), 48230 counts in the MCAL detector (above a background rate of 1170 Hz), and 141030 counts in the AC detector (above a background rate of 3440 Hz). The AGILE ratemeters light curves can be found at http://www.agilescienceapp.it/notices/GRB211229B_AGILE_RM.png .
The event also triggered a partial high time resolution MCAL data acquisition, covering the main peak of the burst, from T1 = 2021-12-29 22:18:45.12 s +/- 0.01 (UTC) to T2 = 2021-12-29 22:18:48.83 +/- 0.01 s (UTC), and released 2354 counts in the detector, above a background rate of 620 Hz. The time-integrated spectrum of the burst in this time interval can be fitted in the energy range 0.4-20 MeV with a power-law with ph. ind. = -2.45 (-0.82/+1.53), resulting in a reduced chi-squared of 1.40 (34 d.o.f.) and a fluence of 1.8e-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/GRB211229B_AGILE_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.