TITLE: GCN CIRCULAR NUMBER: 10340 SUBJECT: GRB 100117A: Magellan IMACS imaging DATE: 10/01/18 06:12:30 GMT FROM: Ryan Chornock at UC Berkeley R. Chornock, E. Berger (Harvard), R. Williams, and D. Kelson (OCIW) report: "We observed the location of the short GRB 100117A (GCN 10336) with IMACS on the Magellan/Baade 6.5-m telescope starting on 2010 Jan 18.042 UT (3.9 hours after the burst). In a 1200 sec stacked R-band image with a seeing of about 1" we detect the same four objects within the XRT error circle (GCN 10336) found in archival CFHT images by Cenko et al. and listed in GCN 10339. All four objects appear to be extended in our image, indicating that one of them may represent the GRB host galaxy. No new sources appear to be present within the XRT error circle, with a 3-sigma limiting magnitude of approximately R=24.7."