TITLE: GCN CIRCULAR NUMBER: 11612 SUBJECT: GRB 110128A: Swift/UVOT observations DATE: 11/01/28 15:44:03 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) & D. Grupe (PSU) report on behalf of the Swift- UVOT team The Swift/UVOT began settled observations of the field of GRB 110128A 144 s after the BAT trigger (Grupe et al., GCN Circ. 11603). The optical afterglow is detected in the first white and u exposures at a refined UVOT position RA(J2000)= 193.89625 deg, DEC(J2000) = 28.06503, which is: RA (J2000) 12:55:35.10 Dec (J2000) 28:03:54.1 with an estimated uncertainty of 1.3 arcsec (radius, 90% confidence). This position is consistent with the optical afterglow detection by NOT (de Ugarte Postigo., GCN Circ 11605) and the enhanced XRT position (Osborne et al., GCN Circ. 11606). Preliminary magnitudes using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for single and summed exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag/3sigUL ##################################################### wh (FC) 144 294 147 20.98 +/- 0.29 u (FC) 302 552 246 20.32 +/- 0.35 wh 582 6352 580 > 21.89 v 632 6763 432 > 20.09 u 707 5943 412 > 20.95 b 558 6148 432 > 21.32 uvw1 682 5738 221 > 20.34 uvm2 658 6874 340 > 20.43 uvw2 608 6558 393 > 20.88 ##################################################### The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).