TITLE: GCN CIRCULAR NUMBER: 31284 SUBJECT: GRB 211219B: AstroSat CZTI detection DATE: 21/12/23 03:18:31 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 211219B which was also detected by Fermi-GBM (GCN 31267). 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 21:49:45.50 UT. The measured peak count rate associated with the burst is 95 (+38, -18) cts/s above the background in the combined data of two quadrants, with a total of 573 (+196, -205) cts. The local mean background count rate was 398 (+2, -2) cts/s. Using cumulative rates, we measure a T90 of 14 (+6, -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 21:49:45.056 UT. The measured peak count rate is 280 (+63, -50) cts/s above the background in the combined Veto data of four quadrants, with a total of 1460 (+257, -400) cts. The local mean background count rate was 1339 (+5, -3) cts/s. We measure a T90 of 8 (+5, -2) s from the cumulative Veto light curve. We also detected another fainter burst, likely from the same source, that lasted for around 6 s in the CsI anticoincidence (Veto) detector about 70 s after the primary burst. 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