TITLE: GCN CIRCULAR NUMBER: 38715 SUBJECT: GRB 241228B: D50 optical detection DATE: 24/12/29 22:35:20 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov martin.jelinek@asu.cas.cz
J. Strobl and M. Jelinek (ASU CAS Ondrejov) report:
We observed the position of the Fermi/GBM-detected GRB 241228B (Fermi GBM team, GCN 38682) observed also by Swift/XRT (Evans, GCN 38688) with the D50 telescope of the Astronomical Institute in Ondřejov, near Prague, Czech Republic. Our observation started 16.4 h after the initial trigger and was performed with an SDSS r' filter.
We detect the optical counterpart (Kumar et al., GCNs 38684 and 38691; An et al., GCN 38687; Ortega-Casas et al., GCN 38692; Ghosh et al., GCN 38702; Xu et al., GCN 38704) in multiple combined 24x120 s frames obtained between 16.4 and 21.9 h after the trigger. Based on our observations, at 18 h after trigger the source had r' = 20.4 +/- 0.1 (AB).
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