TITLE: GCN CIRCULAR NUMBER: 42419 SUBJECT: GRB 251023C: AstroSat CZTI detection DATE: 25/10/24 12:15:05 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), 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 251023C 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 2025-10-23 16:24:32.50 UTC. The measured peak count rate associated with the burst is 682 (+55, -51) counts/s above the background in the combined data of all quadrants, with a total of 4344 (+401, -229) counts. The local mean background count rate was 294 (+1, -7) counts/s. Using cumulative rates, we measure a T90 of 18.2 (+2.8, -1.6) 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 2025-10-23 16:24:28.05 UTC. The measured peak count rate associated with the burst is 942 (+83, -89) counts/s above the background in the combined data of all quadrants, with a total of 5554 (+521, -528) counts. The local mean background count rate was 1676 (+7, -8) counts/s. We measure a T90 of 15.8 (+1.9, -6.2) 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/42419. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...