TITLE: GCN CIRCULAR NUMBER: 15166 SUBJECT: GRB 130831A: Optical Observations via Virtual Telescope, follow-up DATE: 13/09/02 11:21:46 GMT FROM: Gianluca Masi at Bellatrix Astronomical Obs G. Masi (Ceccano, Italy) and F. Nocentini (Frosinone, Italy) report: On Sept 1.9197 2013 UT, we imaged the field around GRB 130831A (GCN 15139) remotely using the the 0.43m-f/6.8 robotic unit part of the Virtual Telescope robotic facility in Italy, about 33 hours after the burst. We co-added 12, 300-seconds unfiltered CCD images and detected the afterglow at the same position we gave in GCN 15152. We performed photometry, assuming R-mags from UCAC-4 for the stars in the field, getting an estimate for the magnitude of 20.7 (CR).