TITLE: GCN CIRCULAR NUMBER: 6919 SUBJECT: GRB 071010B: Keck/LRIS Photometry DATE: 07/10/16 00:12:18 GMT FROM: Daniel Kocevski at UC Berkeley D. Kocevski, D. A. Perley, J. S. Bloom, M. Modjaz, and D. Poznanski (UC Berkeley) report: "In addition to the spectroscopic followup reported by Prochaska et al. (GCN 6890), we acquired a 90s exposure in R band and a 30s exposure in g and V bands of the field containing GRB 071010B with the Keck I 10m telescope (+LRIS), beginning at 15:01:21 UT on 2007-10-11. The optical afterglow at 10:02:9.26, +45:43:50.3 reported by Oksanen et al. (GCN 6871) and confirmed by Kann et al. (GCN 6884 ) was clearly detected. Using aperture photometry, we estimate the multi-color magnitudes of the afterglow to be: R = 19.62 V = 19.71 g = 19.10 when calibrated to Landolt standard star observations. We note that the afterglow had not faded considerably from the magnitude reported by Im et al. (GCN 6897) whose observations began approximately 4 hours earlier.