TITLE: GCN CIRCULAR NUMBER: 31028 SUBJECT: GRB 211024B: Optical afterglow observation by Ondrejov D50 DATE: 21/11/01 21:12:09 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov martin.jelinek@asu.cas.cz
M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report:
We observed the position of the very long GRB 211024B (Gropp et al., GCN 30980, Lien et al. GCN 30989 and Evans et al. GCN 30994) with the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We obtained a set of 175x 60s exposures in Sloan i' filter as soon as the position became accessible above the local horizon, between 3.16 and 6.35h after the trigger.
The optical afterglow (Lipunov et al., GCN 30981; Zhu et al., GCN 30984; Kann et al., GCN 30995; Kuin et al., GCN 31005) is clearly detected in weight-combined images. In particular, we measure i'=19.94+/-0.11 in a 38x60s frame with an exposure mid time T0+0.152d. The calibration was done against Atlas stars in the field.