TITLE: GCN CIRCULAR NUMBER: 31521 SUBJECT: GRB 220124A: AstroSat CZTI detection of a bright long GRB DATE: 22/01/24 08:11:18 GMT FROM: Gaurav Waratkar at IIT,Bombay V. Prasad (IUCAA), G. Waratkar (IITB), A. Suresh (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 ML pipeline (Abraham et al., 2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed detection of a long GRB 220124A. The source, consisting of three distinct bursts, was clearly detected in the 20-200 keV energy range. The strongest peak is at 2022-01-24 03:39:19.00 UT. The measured peak count rate associated with the burst is 441 (+16, -17) cts/s above the background in the combined data of four quadrants, with a total of 25670 (+1334, -1297) cts. The local mean background count rate was 496 (+1, -1) cts/s. Using cumulative rates, we measure a T90 of 231 (+4, -5) s. All three bursts from the source were also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The strongest peak is at 2022-01-24 03:39:24.32 UT. The measured peak count rate is 6829 (+76, -81) cts/s above the background in the combined Veto data of four quadrants, with a total of 362309 (+6293, -4918) cts. The local mean background count rate was 16030 (+5, -11) cts/s. We measure a T90 of 231 (+38, -2) s from the cumulative Veto light curve. We note that the burst has not been localised, and we cannot rule out an association with any SGRs. The ASIMOV tool (http://astrosat-ssc.iucaa.in:8080/ASIMOV/ASIMOV [1]) indicates that other active missions were covering different parts of the sky, hence confirmed non-detections from other missions can help localise the source by inferring earth-occulted regions. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb [2]. 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-ssc.iucaa.in:8080/ASIMOV/ASIMOV [2] http://astrosat.iucaa.in/czti/?q=grb