TITLE: GCN CIRCULAR NUMBER: 42469 SUBJECT: GRB 251025C: AstroSat CZTI detection DATE: 25/10/27 09:48:20 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com> A. Arya (IITB), A. Goyal (IITB), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/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, bright GRB 251025C which was also detected by SWIFT BAT (DeLaunay et. al., GCN Circ. 42412), and CALET (Asaoka et. al., GCN Circ. 42414). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-10-25 23:08:37.50 UTC. The measured peak count rate associated with the burst is 201 (+35, -35) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1467 (+193, -175) counts. The local mean background count rate was 216 (+2, -4) counts/s. Using cumulative rates, we measure a T90 of 18.4 (+1.3, -2.4) s. The source 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 2025-10-25 23:08:37.55 UTC. The measured peak count rate associated with the burst is 475 (+68, -78) counts/s above the background in the combined data of all quadrants, with a total of 3334 (+360, -502) counts. The local mean background count rate was 1311 (+8, -6) counts/s. We measure a T90 of 17.3 (+1.7, -2.0) s from the cumulative Veto light curve. 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. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42469. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...