TITLE: GCN CIRCULAR NUMBER: 41281 SUBJECT: GRB 250807A: AstroSat CZTI detection of bright long burst DATE: 25/08/08 09:48:16 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in> S.Salunke (IUCAA), 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 bright long-duration GRB 250807A which was also detected by Swift/BAT (N. J. Klingler et.al, GCN Circ. 41262), and Konus-Wind (reported through GCN Notices). 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 2025-08-07 10:46:42.50 UTC. The measured peak count rate associated with the burst is 535 (+49, -47) counts/s above the background in the combined data of all quadrants, with a total of 6218 (+449, -269) counts. The local mean background count rate was 275 (+1, -4) counts/s. Using cumulative rates, we measure a T90 of 44 (+2, -3) s. In the preliminary analysis, we find 630 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 2025-08-07 10:46:42.27 UTC. The measured peak count rate associated with the burst is 3662 (+110, -125) counts/s above the background in the combined data of all quadrants, with a total of 36237 (+1153, -1203) counts. The local mean background count rate was 1239 (+5, -6) counts/s. We measure a T90 of 48 (+1, -3) 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/41281. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...