TITLE: GCN CIRCULAR NUMBER: 35267 SUBJECT: GRB 231204A: AstroSat CZTI detection DATE: 23/12/05 14:16:15 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in> G. Waratkar (IITB), P. K. Navaneeth (IUCAA), 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 the long-duration GRB 231204A which was also detected by Fermi-GBM (Fermi GBM Team, GCN Circ. 35258). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2023-12-04 20:00:04.5 UTC. The measured peak count rate associated with the burst is 230.7 (+39.0, -34.4) counts/s above the background in the combined data of all quadrants, with a total of 1319 (+234, -237) counts. The local mean background count rate was 347.5 (+2.1, -2.9) counts/s. Using cumulative rates, we measure a T90 of 13 (+7, -5) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2023-12-04 20:00:06.6 UTC. The measured peak count rate is 873.2 (+83.1, -58.1) counts/s above the background in the combined Veto data of all quadrants, with a total of 6070 (+508, -547) counts. The local mean background count rate was 1532.5 (+4.8, -5.7) counts/s. We measure a T90 of 12 (+8, -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/35267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...