TITLE: GCN CIRCULAR NUMBER: 43926 SUBJECT: GRB 260303A: 1.3m DFOT optical upper limit DATE: 26/03/05 16:36:08 GMT FROM: Debalina Kar at ARIES <kardebalina2000@gmail.com> Debalina Kar, Pankaj Pawar, Anshika Gupta, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303, Wang et al., GCN 43901) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2026-03-03 at 14:54:29.000 UT, approximately 8.88 hours after the trigger. We obtained multiple exposures of 300 s each in the R filter . A total of 10 frames were aligned and stacked to improve the signal-to-noise ratio. In the stacked frame we do not detect any optical counterpart within the error box of SVOM/ECLAIRs (Brunet et al., GCN 43922, Wang et al., GCN 43901) as well as outside the ECLAIRs error circle as reported by Xin et al. (GCN 43916) and (Schneider et al., GCN 43902). This is consistent with the non-detection in the J band reported by Mo et al. (GCN 43915). We derive the following 3-sigma upper limit from the stacked image: Date (UT) Start Time T_start–T0 (hr) Filter Exposure Magnitude ---------------------------------------------------------------------------------- 2026-03-03 14:54:29 ~8.88 R 300 s × 10 > 20.29 The reported magnitude is not corrected for Galactic extinction. Photometric calibration was performed using standard stars from the USNO-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...