TITLE: GCN CIRCULAR NUMBER: 32837 SUBJECT: GRB 221022B: AstroSat CZTI detection DATE: 22/10/25 01:57:14 GMT FROM: Gaurav Waratkar at IIT,Bombay R. Gopalakrishnan (IUCAA), V. Prasad (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/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 the detection of a long GRB 221022B which was also detected by Fermi GBM (GCN 32820), AGILE (Casentini et al., GCN 32822) and Swift/BAT-GUANO (Gayathri et al., GCN 32823). The source was clearly detected in the 20-200 keV energy range. The light curve peaks at 2022-10-22 22:56:11.50 UTC. The measured peak count rate associated with the burst is 1613 (+72, -78) counts/s above the background in the combined data of all quadrants, with a total of 14862 (+774, -850) counts. The local mean background count rate was 494 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 31 (+5, -4) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2022-10-22 22:56:10.86 UTC. The measured peak count rate is 2187 (+97, -105) counts/s above the background in the combined Veto data of all quadrants, with a total of 18217 (+1046, -1027) counts. The local mean background count rate was 1575 (+3, -4) counts/s. We measure a T90 of 27 (+4, -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. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.