TITLE: GCN CIRCULAR NUMBER: 20537 SUBJECT: GRB 170126A: AstroSat CZTI detection DATE: 17/01/27 11:23:28 GMT FROM: Vidushi Sharma at IUCAA V. Sharma, D. Bhattacharya and V. Bhalerao (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 GRB170126A (Swift detection: D. Kocevski et al., GCN Circ. 20530) in quadrant C and D in the 40-200 keV energy range. The light curve shows single peak structure with main peak at 11:30:42 UT, coincident with Swift trigger. The measured peak count rate is 185.7 counts/sec above the background in combined data of four quadrants, with a total 1008.2 counts. The local mean background count rate was 336.3 counts/sec. Using cumulative rates, we measure a T90 of 26.9 secs. It was clearly detected in the CsI anticoincidence detector (Veto) also as bright detection 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.