TITLE: GCN CIRCULAR NUMBER: 45672 SUBJECT: GRB 260920A: AstroSat CZTI detection DATE: 26/09/21 09:20:58 GMT FROM: Anuraag Arya at IIT Bombay A. Arya (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), S. Salunke(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 GRB 260920A which was also detected by Fermi (Fermi GBM team, GCN Circ. 45658). The source was 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 2026-09-20 10:32:38.06 UTC. The measured peak count rate associated with the burst is 234 (+37, -40) counts/s above the background in the combined data of all quadrants, with a total of 1301 (+278, -299) counts. The local mean background count rate was 306 (+4, -4) counts/s. We measure a T90 of 17 (+4, -3) s from the cumulative CZT light curve. 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 2026-09-20 10:32:37.72 UTC. The measured peak count rate associated with the burst is 750 (+60, -66) counts/s above the background in the combined data of all quadrants, with a total of 3370 (+383, -418) counts. The local mean background count rate was 694 (+4, -5) counts/s. We measure a T90 of 16 (+3, -2) s from the cumulative Veto light curve. CZTI data products like interactive and downloadable light curves for this GRB can be found at: https://astrosat.iucaa.in/cift/cift_products/527596334.22/S527596334.22_details.html 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