TITLE: GCN CIRCULAR NUMBER: 30555 SUBJECT: GRB 210730A: AstroSat CZTI detection DATE: 21/07/30 17:16:49 GMT FROM: Gaurav Waratkar at IIT,Bombay V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed the detection of a long GRB 210730A, which was also detected by Swift-BAT (Sonbas et al., GCN 30548, Sakamoto et al., GCN 30554) and Swift-XRT (Beardmore et al., GCN 30550). The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-07-30 04:57:28.55 UT. The measured peak count rate associated with the burst is 502 (+181, -71) cts/s above the background in the combined data of four quadrants, with a total of 621 (+161, -206) cts. The local mean background count rate was 508 (+12, -11) cts/s. Using cumulative rates, we measure a T90 of 3.3 (+1.1, -1.9) 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 [1]. 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. Links: ------ [1] http://astrosat.iucaa.in/czti/?q=grb