TITLE: GCN CIRCULAR NUMBER: 33450 SUBJECT: GRB 230310A: AstroSat CZTI detection DATE: 23/03/10 21:13:29 GMT FROM: Gaurav Waratkar at IIT,Bombay M. Dixit (IITB), 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 a long GRB 230310A which was also detected by Fermi GBM (GCN Circ. 33445). The source was faintly detected in the 20-200 keV energy range. The light curve peaks at 2023-03-10 00:44:58.0 UTC. The measured peak count rate associated with the burst is 96.2 (+25.5, -26.2) counts/s above the background in the combined data of all quadrants, with a total of 562 (+167, -183) counts. The local mean background count rate was 427.7 (+1.7, -2.8) counts/s. Using cumulative rates, we measure a T90 of 10.13 (+3.21, -4.21) s. It was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2023-03-10 00:44:58.0 UTC. The measured peak count rate is 329.8 (+66.1, -68.7) counts/s above the background in the combined Veto data of three quadrants, with a total of 1912 (+530, -584) counts. The local mean background count rate was 2798.0 (+6.4, -7.1) counts/s. We measure a T90 of 13.94 (+3.25, -5.91) 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