TITLE: GCN CIRCULAR NUMBER: 42898 SUBJECT: GRB 251128A: AstroSat CZTI detection DATE: 25/11/29 18:47:43 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com> M. Tembhurnikar (IUCAA), A. Arya (IITB), A. Goyal (IITB), S. Salunke (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 short GRB 251128A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 42865), Swift BAT-GUANO (DeLaunay et. al., GCN Circ. 42874), and Insight-HXMT/HE (Zhang et. al., GCN Circ. 42893). 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 2025-11-28 04:23:02 UTC. The measured peak count rate associated with the burst is 154 (+2, -2) counts/s above the background in the combined data of two quadrants (out of four), with a total of 2558 (+298, -336) counts. The local mean background count rate was 260 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 45.3 (+2.8, -2.2) 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 2025-11-28 04:23:52 UTC. The measured peak count rate associated with the burst is 509 (+72, -62) counts/s above the background in the combined data of all quadrants, with a total of 5062 (+723, -752) counts. The local mean background count rate was 1445 (+6, -5) counts/s. We measure a T90 of 47.1 (+1.9, -2.7) 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/42898. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...