TITLE: GCN CIRCULAR NUMBER: 31180 SUBJECT: GRB 211206A: AstroSat CZTI detection DATE: 21/12/07 10:12:35 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 211206A which was also detected by AGILE/MCAL (Ursi et al., GCN 31175) and Swift/BAT-GUANO (DeLaunay et al., GCN 31176). The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2021-12-06 19:51:12.450 UT. The measured peak count rate associated with the burst is 776 (+198, -60) cts/s above the background in the combined data of two quadrants, with a total of 1947 (+221, -223) cts. The local mean background count rate was 443 (+7, -10) cts/s. Using cumulative rates, we measure a T90 of 4.3 (+1.3, -0.6) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2021-12-06 19:51:12.088 UT. The measured peak count rate is 1509 (+86, -95) cts/s above the background in the combined Veto data of four quadrants, with a total of 5582 (+310, -365) cts. The local mean background count rate was 1466 (+4, -4) cts/s. We measure a T90 of 6.6 (+1.5, -1.6) 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