TITLE: GCN CIRCULAR NUMBER: 10343 SUBJECT: GRB 100117A: Optical object inside the revised XRT error circle DATE: 10/01/18 16:23:10 GMT FROM: Alexander Kann at TLS Tautenburg D. Alexander Kann (TLS Tautenburg), D. Malesani (DARK/NBI), D. Xu (WIS, DARK/NBI) report on behalf of a larger collaboration: Using the improved XRT position (B. Sbarufatti et al. GCN 10342) for the Swift short/hard GRB 100117A (M. de Pasquale et al., GCN 10336), we find that the afterglow candidate reported from NOT observations (D. Xu et al., GCN 10337), which is probably identical to source "S1" from S. B. Cenko et al. (GCN 10339), lies outside the error circle. We therefore consider it unlikely that this object is related to the GRB, also considering the lack of pronounced variability (S. B. Cenko et al. GCN 10339). Of the four sources reported by S. B. Cenko et al. (GCN 10339) and confirmed by R. Chornock et al. (GCN 10340) and A. Cucchiara et al. (GCN 10341), only source "S3" still lies within the new XRT error circle. Source S3, which is extended according to the above reports, may be the host galaxy of GRB 100117A, although lack of variability does not allow a conclusive statement. An additional image epoch to perform image subtraction is encouraged. This message may be cited.