TITLE: GCN CIRCULAR NUMBER: 31283 SUBJECT: GRB 211219A: AstroSat CZTI detection DATE: 21/12/23 03:06:33 GMT FROM: Gaurav Waratkar at IIT,Bombay V. Prasad (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed detection of a long GRB 211219A which was also detected by Fermi (GCN 31265), MASTER-Net (Lipunov et al. GCN 31268), Swift/BAT-GUANO (Tohuvavohu et al., GCN 31269) and AGILE (Ursi et al., GCN 31270). The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-12-19 14:55:22.50 UT. The measured peak count rate associated with the burst is 178 (+42, -26) cts/s above the background in the combined data of two quadrants, with a total of 912 (+201, -218) cts. The local mean background count rate was 382 (+2, -3) cts/s. Using cumulative rates, we measure a T90 of 15 (+3, -8) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2021-12-19 14:55:23.063 UT. The measured peak count rate is 740 (+72, -70) cts/s above the background in the combined Veto data of four quadrants, with a total of 3100 (+285, -308) cts. The local mean background count rate was 1243 (+4, -5) cts/s. We measure a T90 of 11.0 (+0.3, -5.2) s from the cumulative Veto light curve. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. Links: ------ [1] http://astrosat.iucaa.in/czti/?q=grb