TITLE: GCN CIRCULAR NUMBER: 30737 SUBJECT: GRB 210826A: AstroSat CZTI detection DATE: 21/08/28 14:30:28 GMT FROM: Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in> 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 detection of a long GRB 210826A, which was also detected by Fermi-GBM (trigger no. 210826293, GCN 30716) and Fermi-LAT (Ohno et al., GCN 30721). 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 2021-08-26 07:01:53.50 UT. The measured peak count rate associated with the burst is 183 (+45, -24) cts/s above the background in the combined data of four quadrants, with a total of 2161 (+327, -549) cts. The local mean background count rate was 560 (+4, -2) cts/s. Using cumulative rates, we measure a T90 of 24 (+17, -10) s. It was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-08-26 07:01:47.03 UT. The measured peak count rate is 200 (+95, -5) cts/s above the background in the combined Veto data of four quadrants, with a total of 1953 (+648, -720) cts. The local mean background count rate was 1907 (+6, -6) cts/s. We measure a T90 of 14 (+8, -5) s from the cumulative Veto light curve. 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