TITLE: GCN CIRCULAR NUMBER: 22638 SUBJECT: GRB 180411A: Swift/UVOT Upper Limit DATE: 18/04/12 10:53:05 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and Z. Liu (NAOC/U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began observations of the field of GRB 180411A 64 s after the BAT trigger (Liu et al., GCN Circ. 22630) with a settling exposure in the V filter. The UVOT safety circuit tripped 3.4s into the following UV grism exposure, most likely due to the bright star HD223128, 5.08 arcmin from the burst position. No optical afterglow consistent with the enhanced XRT position (Gibson et al. GCN Circ. 22632) is seen in the 9.3s V settling exposure to a preliminary 3-sigma upper limit of 16.8 mag using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373). The magnitude is not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.104 in the direction of the burst (Schlegel et al. 1998).