TITLE: GCN CIRCULAR NUMBER: 16830 SUBJECT: GRB 140916B: LOT and iPTF follow-up of optical afterglow candidates DATE: 14/09/18 02:13:09 GMT FROM: Kuiyun Huang at ASIAA GRB 140916B: LOT and iPTF follow-up of optical afterglow candidates L. P. Singer (Caltech), K.Y. Huang (NCU/NTNU/ASIAA), Y. Urata (NCU), V. Bhalerao (IUCAA), M. M. Kasliwal (Carnegie Observatories/Princeton), and S. B. Cenko (NASA/GSFC) report on behalf of a larger collaboration: We have continued to observe the optical afterglow candidates reported by iPTF (Singer et al., GCN 16822) in connection with GRB 140916B, which was detected by Fermi. We obtained images of iPTF14fok with the Lulin One-meter Telescope (LOT), the Palomar 48-inch Oschin telescope (P48), and the robotic Palomar 60-inch telescope (P60). We report the following observations, relative to the time of the burst: LOT, +13.16 hours: r = 19.87 +/- 0.18 P60, +29.67 hours: r = 19.02 +/- 0.22 The source has not faded significantly from the initial P48 detection 4.17 hours after the burst of R = 19.57 +/- 0.07 mag. We therefore conclude that it is unrelated to the GRB, possibly an old foreground supernova. This message can be cited.