TITLE: GCN CIRCULAR NUMBER: 10591 SUBJECT: GRB 100413A: Swift/UVOT Upper Limits DATE: 10/04/14 17:07:25 GMT FROM: Frank Marshall at GSFC F.E. Marshall (NASA/GSFC) and S.T. Holland (CRESST/USRA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100413A 150 s after the BAT trigger (Holland et al., GCN Circ. 10581). No optical afterglow consistent with the enhanced XRT position (Goad et al., GCN Circ. 10584) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 150 300 147 >20.5 u_FC 308 558 246 >20.5 white 150 6231 589 >21.8 v 639 6641 490 >20.4 b 564 7321 353 >20.7 u 308 7256 717 >20.7 w1 688 7051 471 >20.5 m2 663 6846 490 >20.4 w2 614 6436 491 >20.8 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.11 in the direction of the burst (Schlegel et al. 1998).