TITLE: GCN CIRCULAR NUMBER: 31099 SUBJECT: GRB 211118A: AstroSat CZTI detection DATE: 21/11/20 18:21:36 GMT FROM: Gaurav Waratkar at IIT,Bombay V. Prasad (IUCAA), P. Sawant (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 GRB 211118A, which was also detected by Swift/BAT-GUANO (Raman et al., GCN 31096). 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 2021-11-18 23:38:13.65 UT. The measured peak count rate associated with the burst is 915 (+217, -92) cts/s above the background in the combined data of two quadrants, with a total of 806 (+94, -109) cts. The local mean background count rate was 446 (+7, -8) cts/s. Using cumulative rates, we measure a T90 of 2.2 (+0.6, -0.4) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. 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