TITLE: GCN CIRCULAR NUMBER: 43958 SUBJECT: GRB 260310A: AstroSat CZTI detection of a long burst DATE: 26/03/11 07:19:18 GMT FROM: Anuraag Arya at IIT Bombay S. Salunke (IUCAA), Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), 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 GRB 260310A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43951). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-03-10 04:57:12.05 UTC. The measured peak count rate associated with the burst is 273 (+67, -57) counts/s above the background in the combined data of all quadrants, with a total of 2709 (+573, -589) counts. The local mean background count rate was 1494 (+6, -6) counts/s. We measure a T90 of 30 (+2, -8) s from the cumulative Veto light curve. The source was also clearly detected in the 20-200 keV energy range. 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