GCN Circular 27860

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), M. Blazek, C. C. Thoene, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), and I. Hermelo (CAHA) report:

We observed the XRT error circle (Evans et al., GCN #27836) of the 
bright GRB 200528A (Swift detection: Ambrosi et al., GCN #27832; Fermi 
GBM detection: The Fermi GBM team, GCN #27831) with the 2.2m telescope 
at CAHA (Almeria, Spain), equipped with the CAFOS detector. We obtained 
21 x 180 s exposures in the Ic band under adverse observing conditions 
(moonlight, bad seeing and transparency).

At the enhanced XRT position, we detect no source (but would have 
preferred to). We derive a 3 sigma limiting magnitude of Ic > 23.5 mag 
(Vega) at 0.440865 days after the GRB, calibrated against SDSS standard 
stars transformed to the Ic band following Lupton (2005). This limit is 
comparable to those achieved by NOT about an hour later (Malesani et 
al., GCN #27842).