GCN Circular 19847
S. Jeong (SKKU/IAA-CSIC), I. H. Park (SKKU), Y. Hu (IAA-CSIC), R. Scarpa (GTC) and A. J. Castro-Tirado (IAA-CSIC), on behalf of a larger collaboration report: We observed the field of the short GRB 160821B detected by Swift (Siegel et al. GCNC 19833) and Fermi (Stanbro et al. GCNC 19843) using the 10.4m Gran Telescopio Canarias (GTC) equipped with OSIRIS. Observations started at 00:16:17.480 UT on Aug 22 (i.e., 1.78 hr after the burst), in the riz-band filters. We also detect the point-like source proposed by Xu et al. (GCNC 19834) as a potential afterglow candidate) within the XRT error circle reported by Siegel et al. (GCNC 19833), for which we measure a preliminary magnitude (pending final calibration) of R = 22.40+/-0.06 at 1.83 hr after the burst. Lacking variability, unless there is an initial plateau phase lasting several hour in the afterglow brightness, this would be consistent with a host galaxy detection. Further GTC observations are planned. We thanks D. Xu and D. Malesani for providing secondary reference stars in the field.