GCN Circular 22143
V. Sharma 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 GRB 171120A, which was also detected by Swift-BAT (Tohuvavohu et al., GCN 22133), Fermi-GBM (trigger 532876807/171120556) and Fermi-LAT (Longo F. et al., GCN 22136). The source was clearly detected in the 40-200 keV energy range. The light curve of the CZT detector shows a single peak of emission at 13:20:02 UT. The measured peak count rate is 367.4 cts/s above the background in combined data of four quadrants, with a total of 634 cts. The local mean background count rate was 307.6 cts/s. Using cumulative rates, we measure a T90 of 6.8 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The Veto light curve shows a strong peak coincident with the peak in the CZT detector and a weaker second peak ~39 s later. 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.