TITLE: GCN CIRCULAR NUMBER: 26632 SUBJECT: GRB 200101A : AstroSat CZTI detection DATE: 20/01/02 17:58:05 GMT FROM: Ramkrishna Gaikwad at IUCAA/AstroSat R. Gaikwad, S. Gupta, 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 a GRB 200101A, which was also detected by Fermi GBM Final Real-time Localization (GCN #26624), Global MASTER-Net (Lipunov V. et al., GCN #26626), BALROG localization (Kunzweiler F. et al., GCN #26625) and Fermi GBM (Veres P. et al., GCN #26627). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peak of emission with strongest peak at 2020-01-01 20:39:27.0 UT. The measured peak count rate associated with the burst is 1588 cts/s above the background in the combined data of four quadrants, with a total of 6659 cts. The local mean background count rate was 570 cts/s. Using cumulative rates, we measure a T90 of 16.69 s. In preliminary analysis, we find that 497 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.