TITLE: GCN CIRCULAR NUMBER: 38733 SUBJECT: GRB 241228B: SAO RAS optical observations DATE: 24/12/30 21:08:56 GMT FROM: Moskvitin Alexander at SAO RAS <mosk@sao.ru> A. S. Moskvitin, O. I. Spiridonova, Yu. V. Sotnikova (SAO RAS), A. Volnova, A. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), report on behalf of the GRB follow-up team. We observed the field of GRB 241228B discovered by Fermi (Fermi GBM team, GCN 38682; Scotton and Meegan, GCN 38714), Swift (Evans, GCN 38688; Burrows et al., GCN 38713) with the 1-m telescope of SAO RAS Zeiss-1000 equipped with the CCD-photometer on December 29, 21:49:11 -- 22:57:57 UT (t_mid - T0 = 1.7573 days). We obtained 12 x 300 sec. images in Rc band. The GOTO24jmz optical counterpart (Kumar et al., GCN 38684, GCN 38691; An et al. GCN 38687; Ortega-Casas et al., GCN 38692; Ghosh et al., GCN 38702; An et al., GCN 38704; Volnova et al., GCN 38709; Strobl and Jelinek, GCN 38715) is clearly detected in the stacked image with the brightness of R = 20.97 +/- 0.06. Based on photometry in R filter (this report and photometry by Volnova et al., GCN 38709) we found that the light curve of the afterglow of GRB 241228B/GOTO24jmz can be fitted with a simple power-law model with an power law index of -0.66. The photometry is based on nearby SDSS stars used by Volnova et al., GCN 38709 (magnitudes were converted with Lupton 2005 equations). View this GCN Circular online at https://gcn.nasa.gov/circulars/38733. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...