TITLE: GCN CIRCULAR NUMBER: 35069 SUBJECT: GRB 231111A: Swift/UVOT Detection DATE: 23/11/17 00:10:52 GMT FROM: Sam LaPorte at PSU GRB 231111A: Swift/UVOT Detection S. J. LaPorte (PSU) and A. Melandri (INAF-OAR) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 231111A 165 s after the BAT trigger (Melandri et al., GCN Circ. 34981). A source consistent with the XRT position (Evans et al., GCN Circ. 34991) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 19:20:45.25 = 290.18856 (deg.) Dec (J2000) = +52:26:10.5 = 52.43624 (deg.) with an estimated uncertainty of 0.43 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 b 26598 27505 885 >20.41 uvm2 34150 34575 418 >20.05 u 180 418 234 16.52 v 33541 34144 590 >19.85 uvw1 38947 39736 776 >20.24 uvw2 27512 85141 1176 >20.65 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.117 in the direction of the burst (Schlegel et al. 1998).