D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH, DARK/NBI), C. C.
Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), A.
Guijarro, and P. Martin-Fernandez (both CAHA) report:
We observed the optical afterglow of the very long Swift GRB 211024B
(Gropp et al., GCN #30980; Zhu et al., GCN #30984) with CAFOS mounted on
the 2.2m Telescope at Calar Alto, Almeria, Spain. We obtained 30 x 90 s
in the SDSS i' band under mediocre conditions.
At the position of the GRB afterglow discovered by Nanshan/NEXT (Zhu et
al., GCN #30984), we detect a source. Against one Pan-STARRS comparison
star, we measure:
i' = 20.27 +\- 0.05 mag (AB) at 0.2485 d after the GRB.
We note the XRT light curve at time of writing
(https://www.swift.ac.uk/xrt_curves/01081073/ Evans et al., GCN #30994)
shows a certain resemblance to that of the ultra-long GRB 111209A, being
relatively flat until 10 ks before dropping off very steeply. The lack
of early data prevents further conclusions for now. Further follow-up is