TITLE: GCN CIRCULAR NUMBER: 20951 SUBJECT: GRB 170329A: AstroSat CZTI detection DATE: 17/03/31 09:31:04 GMT FROM: Vidushi Sharma at IUCAA V. Sharma(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed clear detection of GRB170329A (Fermi GBM detection: E.Bissaldi et al., GCN Circ. 20943) in the 40-200 keV energy range. The light curve shows single peak emission with peak counts at 09:17:08.940 UT, 2 s after the Fermi trigger. The measured peak count rate is 161.1 counts/s above the background in combined data of four quadrants, with a total 879 counts. The local mean background count rate was 387.9 counts/s. Using cumulative rates, we measure a T90 of 14.1 s. It was clearly detected in the CsI anticoincidence detector (Veto) also 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.