TITLE: GCN CIRCULAR NUMBER: 28651 SUBJECT: GRB 201016A: AstroSat CZTI detection DATE: 20/10/16 11:27:57 GMT FROM: Soumya Gupta at IUCAA/ASTROSAT S. Gupta, V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (IUCAA/TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed detection of a bright long GRB 201016A, which was also detected by Fermi GBM Final Real-time (GCN #28636), BALROG (Biltzinger B. et al., GCN #28641) and Fermi GBM (Wood J. et al., GCN #28646). The source was clearly detected in the 40-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-10-16 00:27:56.500 UT. The measured peak count rate associated with the burst is 4218 +/- 68 cts/s above the background in the combined data of four quadrants, with a total of 8601 +/- 8 cts. The local mean background count rate was 488 +/- 1 cts/s. Using cumulative rates, we measure a T90 of 2.91 +/- 0.01 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-10-16 00:27:56.000 UT. The measured peak count rate is 6766 +/- 89 cts/s above the background in the combined Veto data of four quadrants, with a total of 14638 +/- 12 cts. The local mean background count rate was 1422 +/- 1 cts/s. We measure a T90 of 3.05 +/- 0.01 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. 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.