GCN Circular 21087
A. Cucchiara, D. Morris (U. of Virgin Islands), C. Guidorzi (U. Ferrara), B. Gendre (U. of Virgin Islands), reports on behalf of a larger collaboration: "On May 10 at 16:46 UT (T_0 +11.4h) we began observing the center of the field of LAT GRB 170510A (Bissaldi et al. GCN #21080) using the Las Cumbres Observatory 1m Sutherland facility. We covered 50% of the LAT error region and we obtained a series of 5x120s observations in R band, for a total of 10 minutes on sky. We identified a possible optical counterpart of GRB170510A located at the same position of candidate #1 from the Swift-XRT tiled observations (Evans et al. GCN #21082, Melandri et al. GCN #21086). Our preliminary photometry for this source is: R = 19.6 +/- 0.2 mag At the moment we cannot establish the temporal variability of this source. This magnitude is calibrated against nearby USNO-B1 sources, and is not corrected for Galactic Extinction."