TITLE: GCN CIRCULAR NUMBER: 22312 SUBJECT: GRB 171223A; AstroSat CZTI detection DATE: 18/01/10 06:16:48 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 short GRB 171223A, which was also detected by Fermi-GBM (Stanbro M. et al., GCN 22278) and Insight-HXMT/HE (Li Z. W. et al., GCN 22286). The source was clearly detected in the 40-200 keV energy range. The light curve shows single peak structure with peak at 19:38:15.150 UT. The measured peak count rate is 1464.1 cts/s above the background in combined data of four quadrants, with a total of 2594 cts. The local mean background count rate was 485 cts/s. Using cumulative rates, we measure a T90 of 0.27 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.