GCN Circular 16711
F.J. Aceituno (OSN/IAA-CSIC), J. Gorosabel (IAA-CSIC/UPV-EHU) and A.J. Castro-Tirado (IAA-CSIC/UMA), report on behalf of a larger collaboration: We observed the field of GRB 140818B (Vargas et al., GCN 16709) with the 1.5m OSN telescope at Observatorio de Sierra Nevada (Spain). Several 300s images were acquired in the I- and R-band starting on Aug 18, 20:15 UT (i.e. 1.5 hours post burst). An optical source at the edge of the Swift/XRT error box is detected at coordinates (J2000) RA: 18 04 32.47, Dec: -01 23 09.8 (+/- 1"), which is not present in the corresponding DSS-2 image. A preliminary photometry against the USNO B1.0 catalog yields an I-band magnitude of 19.7 (Vega). At the moment we cannot determine if the source if fading in brightness. Further observations are encouraged.