TITLE: GCN CIRCULAR NUMBER: 38702 SUBJECT: GRB 241228B: LCO optical observation DATE: 24/12/29 03:35:55 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994@gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration. We observed the field of the GRB 241228B triggered by Fermi (Fermi GBM team, GCN 38682) in B filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Siding Spring New South Wales, Australia. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on December 28, 2024, starting from 10.97 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs (Kumar et al., GCN 38684 and GCN 38691, An et al. GCN 38687) in our B band image. Date UTstart JD t-T0 (hours) Exp (sec) Filter Magnitude 2024-12-28 15:11:37.24 2460673.13307 10.97 1 x 1200 B B = 21.35 +/- 0.03 The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/38702. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...