TITLE: GCN CIRCULAR NUMBER: 19656 SUBJECT: GRB 160703A: Swift/UVOT Detection DATE: 16/07/05 18:44:25 GMT FROM: Lea Hagen at PSU L. M. Z. Hagen (PSU) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160703A 75 s after the BAT trigger (Cenko et al., GCN Circ. 19645). We detect a fading source consistent with the XRT position (D'Elia et al. GCN Circ. 19655) and optical detections (Tachibana et al., GCN Circ. 19652; Kuroda et al., GCN Circ. 19653). Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 75 225 147 14.09+-0.02 white 567 1014 186 16.64+-0.03 white 4890 5090 196 18.33+-0.05 v 617 1064 58 16.51+-0.10 v 5300 5500 196 18.34+-0.17 b 543 735 38 16.38+-0.06 b 4685 4885 196 18.76+-0.11 u 288 537 245 15.05+-0.03 u 691 710 19 15.88+-0.09 u 4480 4680 196 17.79+-0.08 uvw1 666 1113 58 16.80+-0.12 uvm2 642 1089 58 17.75+-0.25 uvm2 5505 5695 187 19.07+-0.29 uvw2 593 1040 58 18.38+-0.27 uvw2 5096 5295 196 19.45+-0.30 The detection in all UVOT filters is consistent with a redshift of z < ~1.5. The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.15 in the direction of the burst (Schlegel et al. 1998).