TITLE: GCN CIRCULAR NUMBER: 31863 SUBJECT: GRB 220408B: AstroSat CZTI detection DATE: 22/04/09 11:38:11 GMT FROM: Gaurav Waratkar at IIT,Bombay R. Gopalakrishnan (IUCAA), V. Prasad (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., 2021, JApA, 42, 73) showed detection of a long GRB 220408B which was also detected by Fermi-GBM (GCN 31854). 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 2022-04-08 07:28:08.50 UT. The measured peak count rate associated with the burst is 1181 (+79, -36) counts/s above the background in the combined data of all four quadrants, with a total of 12408 (+531, -419) counts. The local mean background count rate was 516 (+2, -4) counts/s. Using cumulative rates, we measure a T90 of 25 (+3, -1) s. It was also clearly 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 2022-04-08 07:28:08.19 UT. The measured peak count rate is 1215 (+93, -70) counts/s above the background in the combined Veto data of four quadrants, with a total of 10873 (+743, -663) counts. The local mean background count rate was 1882 (+4, -5) counts/s. We measure a T90 of 24 (+2, -6) 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