TITLE: GCN CIRCULAR NUMBER: 43846 SUBJECT: GRB 260226A: AstroSat CZTI detection of bright long burst DATE: 26/02/26 15:00:12 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com> Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), U. Pathak (IITB), 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 260226A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43840), Fermi LAT (Depalo et. al. , GCN Circ. 43844) and Calet (via Trigger Notices, Trig Num. 1456137494). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. Due to the extremely bright nature of the GRB, all four quadrants of CZT detectors were saturated. The strongest non-saturated peak of the lightcurve occurs at 2026-02-26 10:38:22.65 UTC. This affects the total counts and peak counts reported. The measured peak count rate associated with the burst is 2464 (+267, -180) counts/s above the background in the combined data of three quadrants (out of four), with a total of 6666 (+247, -284) counts. We caution that these numbers are impacted by the data loss from saturation. The local mean background count rate was 258 (+1, -5) counts/s. Using cumulative rates, we measure a T90 of 21 (+1, -1) s. In the preliminary analysis, we find 4947 Compton events associated with this event. 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 2026-02-26 10:38:15.33 UTC. The veto detector does not show any signs of saturation. The measured peak count rate associated with the burst is 16447 (+216, -227) counts/s above the background in the combined data of all quadrants, with a total of 139460 (+832, -794) counts. The local mean background count rate was 1425 (+4, -6) counts/s. We measure a T90 of 19 (+1, -1) 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/43846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...