GCN Circular 21244
W. Fong, B. Rothberg, J. Hill, P. Milne, N. Smith and D. Zaritsky (University of Arizona) report on behalf of the AZTEC (Arizona Transient Exploration and Characterization) team: "We observed the field of the Fermi/LAT candidate (Omodei et al., GCN 21227) with the Large Binocular Camera (LBC) mounted on the 2x8.4-meter Large Binocular Telescope (LBT) on Mount Graham, Arizona beginning on 2017 Jun 10.156 UT (2.07 days post-trigger; LSC/Virgo et al. GCN 21221). We obtained 26x30-sec of i-band imaging in 1.7" seeing at a mean airmass of 2.2. The observations cover 88% of the Fermi/LAT localization region (90% confidence; Omodei et al., GCN 21227), as well as the positions of Swift/XRT Sources 1-4 (Evans et al.; GCN 21233). Inspection of the LBT observations relative to Pan-STARRS1 archival imaging reveals no new sources in or around the positions of XRT Sources 1-4. Moreover, photometry of the known optical sources are consistent with the archival PS1 and SDSS values within the 1-sigma uncertainties, corroborating the conclusions from shallower imaging with NOWT (Xu et al., GCN 21236) and Swift/UVOT (Emery et al., GCN 21235). Calibrated to SDSS stars in the field, we estimate a 3-sigma limiting magnitude of i_AB>22.4 mag for the observations. We thank LBT Director Christian Veillet for awarding this observing time."