GCN Circular 21245
W. Fong, 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 Wide Field Camera (WFCAM) mounted on the 3.8-m United Kingdom Infrared Telescope (UKIRT) on Mauna Kea beginning on 2017 Jun 9.238 UT (1.15 days post-trigger; LSC/Virgo et al. GCN 21221). We obtained a total of 360-sec of J-band imaging in 1.4" seeing at a mean airmass of 1.8. The observations cover the entire Fermi/LAT localization region (90% confidence; Omodei et al., GCN 21227), as well as the positions of all Swift/XRT sources reported in Evans et al. (GCN 21233). To assess variability, we obtained a second set of observations beginning on 2017 Jun 10.240 UT (2.16 days post-trigger and 24.0 hr after the initial UKIRT observations). These observations cover only 75% of the Fermi/LAT localization area, as well as the positions of XRT Sources 2-7. We perform photometry of all known near-IR sources in or around the positions of the XRT sources, and find no evidence for variability relative to archival 2MASS values. Digital image subtraction of the two UKIRT epochs using the ISIS software package reveals no residuals, indicating no variability from 1.15 to 2.16 days post-trigger for 75% of the LAT localization region, to a 3-sigma limit of J>18.9 AB mag. We note that this preliminary analysis is based on reductions produced by the quick-look pipeline ORAC-DR, and a final reduction of the images are expected to be at least ~1.5 mag deeper. We thank Sam Benigni and Watson Varricatt for their assistance in planning and executing these observations."