TITLE: GCN CIRCULAR NUMBER: 22168 SUBJECT: GRB 171124A: AstroSat CZTI detection DATE: 17/11/24 21:17:53 GMT FROM: Vidushi Sharma at IUCAA 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 171124A, which was also detected by Fermi-LAT (Longo F. et al., GCN 22156) and Fermi-GBM (Bissaldi E. et al., GCN 22164). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 05:38:00.500 UT, ~4 s after the Fermi trigger. The measured peak count rate is 161.3 cts/s above the background in combined data of four quadrants, with a total of 1157 cts. The local mean background count rate was 424.7 cts/s. Using cumulative rates, we measure a T90 of 8.4 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. 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.