GCN Circular 30356
N. P. M. Kuin (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210702A 104 s after the BAT trigger (Lien et al., GCN Circ. 30351). A source consistent with the XRT position (Lien et al. GCN Circ. 30351) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 11:14:18.70 = 168.57793 (deg.) Dec (J2000) = -36:44:50.0 = -36.74723 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). 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 104 254 147 15.70 +/- 0.02 b 3516 3716 197 15.46 +/- 0.03 u 316 361 44 11.37 +/- 0.05 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.121 in the direction of the burst (Schlegel et al. 1998).