TITLE: GCN CIRCULAR NUMBER: 23817 SUBJECT: GRB 190129B: AstroSat CZTI detection DATE: 19/01/30 14:42:38 GMT FROM: Tanazza Khanam at IUCAA T. Khanam, V. Sharma, D. Bhattacharya and A. Vibhute (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 long GRB 190129B, which was also detected by IPN Triangulation (Hurley K. et al., GCN Circ. 23808), Konus-Wind (Frederiks D. et al., GCN Circ 23809), Swift (Evans P. A. et al., GCN Circ 23812 and LaPorte S. J. et al., GCN Circ 23813) and GROND (Bolmer J. et al,. GCN Circ 23814). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 12:15;45.5 UT. The measured peak count rate is 3638 cts/s above the background in combined data of four quadrants, with a total of 29852 cts. The local mean background count rate was 601 cts/s. Using cumulative rates, we measure a T90 of 15.83 s. In preliminary analysis, we find that 2588 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.