TITLE: GCN CIRCULAR NUMBER: 12194 SUBJECT: GRB 110721A: Preliminary Swift/UVOT Upper Limits DATE: 11/07/25 15:13:56 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/USRA/GSFC), and C. A. Swenson (PSU) report on behalf of the Swift/UVOT team: Swift/UVOT began observations of the field of the weak X-ray source that may be associated with GRB 110721A (Greiner et al., 2011, GCNC 12192) 54,869 s after the Fermi/GBM trigger (Tierney & von Kienlin, 2011, GCNC 12187). We do not detect the GROND optical source in the UVOT images. Our preliminary upper limits are consistent with the faint nature of the GROND source. The 3-sigma UVOT upper limits are Filter T_start(s) T_stop(s) Exp(s) Upper Limit ---------------------------------------------------------- v 56,146 56,853 672 >20.8 u 54,867 55,509 632 >21.4 white 55,516 56,158 632 >22.4 ---------------------------------------------------------- These upper limits are on the UVOT photometric system of Poole et al., 2008, MNRAS, 383, 627). The upper limits are not corrected for the Galactic extinction due to the reddening of E_{B-V} = 0.02 mag in the direction of the burst (Schlegel et al., 1998, ApJS, 500, 525).