TITLE:   GCN CIRCULAR
NUMBER:  28794
SUBJECT: GRB 201027A: 1.5m OSN optical upper limit
DATE:    20/10/27 16:06:00 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, F. J. Aceituno, A. J. Castro-Tirado, E. Fernandez-Garcia (IAA-CSIC) on behalf of a larger collaboration, report:

Following the detection of GRB201027A by Swift (Cenko et al. GCNC 28788), optical images in the I-band were obtained at the 1.5m OSN telescope in Granada (Spain) starting at 04:29 (Oct 27), i.e. ~3.4 h post burst. No optical afterglow is detected in the co-added image within the enhanced Swift/XRT error box (Osborne et al. GCNC 28792) down to I=21.9, which is consistent with the non-detection reported by Swift/UVOT (GCNC 28788).

We thank the staff at OSN for their excellent support.