TITLE: GCN CIRCULAR NUMBER: 27371 SUBJECT: GRB 200311A: AstroSat CZTI detection DATE: 20/03/12 08:29:18 GMT FROM: Soumya Gupta at IUCAA/ASTROSAT S. Gupta, V. Sharma, A. Vibhute and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of a GRB 200311A, which was also detected by Fermi GBM (GCN #27363), AGILE/MCAL (Ursi A. et al., GCN #27365) and Global MASTER-Net (Lipunov V. et al., GCN #27370). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with the strongest peak at 2020-03-11 15:16:13.516 UT. The measured peak count rate associated with the burst is 958 +/- 38.4 cts/s above the background in the combined data of four quadrants, with a total of 10660 +/- 42.9 cts. The local mean background count rate was 532 +/- 1.0 cts/s. Using cumulative rates, we measure a T90 of 30.5 +/- 0.03 s. In preliminary analysis, we find that 1186 Compton events are associated with this event. 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. 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.