GCN Circular 17411
A. Breeveld (MSSL-UCL), D. Malesani (DARK/NBI) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 150204A during follow-up observations, 51182 s after the BAT trigger (Cummings et al. GCN Circ. 17404). No optical afterglow consistent with the possible XRT counterpart (A. Melandri et al. GCN Circ. 17409) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag v 57368 58276 885 >19.5 u 52088 52670 568 >19.5 w1 51182 63642 1495 >20.3 m2 58281 63016 1027 >20.1 w2 56461 57361 886 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.824 in the direction of the burst (Schlegel et al. 1998).