TITLE: GCN CIRCULAR NUMBER: 41438 SUBJECT: GRB 250818A: AstroSat CZTI detection DATE: 25/08/20 09:19:25 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in> Harsha K. H. (IUCAA), Anuraag Arya (IITB), G. Waratkar (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-duration GRB 250818A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 41402), and Swift/BAT (Cenko et. al., GCN Circ. 41403). The source was 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 2025-08-18 01:32:39.98 UTC. The measured peak count rate associated with the burst is 214 (+77, -0) counts/s above the background in the combined data of all quadrants, with a total of 6518 (+769, -832) counts. The local mean background count rate was 1187 (+3, -3) counts/s. We measure a T90 of 89 (+7, -5) 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/41438. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...