TITLE: GCN CIRCULAR NUMBER: 15045 SUBJECT: GRB 130725B: Swift/UVOT Observations DATE: 13/07/26 17:50:43 GMT FROM: Frank Marshall at GSFC S. R. Oates (UCL-MSSL) and C. A. Swenson (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130725B 72 s after the BAT trigger (Swenson et al. GCN Circ. 15029; Swenson GCN Circ. 15044). A source consistent with the enhanced XRT position (Sbarufatti and Swenson GCN Circ. 15040) is detected in the initial UVOT exposures in all filters except for uvm2 and uvw2. The non-detection in these filters suggests a redshift ~<2. The preliminary UVOT position is: RA (J2000) = 14:16:57.76 = 214.24068 (deg.) Dec (J2000) = -11:07:41.8 = -11.12827 (deg.) with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits 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 72 221 147 16.67 +/- 0.03 v 614 6315 252 19.16 +/- 0.27 b 540 559 19 18.20 +/- 0.28 u 284 534 246 17.35 +/- 0.06 w1 663 6725 236 20.01 +/- 0.36 m2 6320 16621 1003 >21.1 w2 4265 4465 197 >20.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.061 in the direction of the burst (Schlegel et al. 1998).