GCN Circular 15894
M. H. Siegel (PSU), F. E. Marshall (NASA/GSFC) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: Swift/UVOT started observations of GRB140226A/iPTF14yb (Cenko et al., GCN Circ. 15833) 25718 s after the IPN trigger (Hurley et al., GCN Circ. 15888). No optical counterpart is detected at the position of the iPTF or XRT positions (Beardmore et al., GCN Circ 15884) in summed exposures. Preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al al. 2011, AIP Conf. Proc. 1358, 373) is: Filter T_start (s) T_stop (s) Exp(s) Mag uvm2 25718 43672 2180 >21.24 v 124093 136265 4877 >20.96 v 147705 154552 1822 >20.54 No correction has been made for the expected Galactic extinction corresponding to E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).