GCN Circular 17635

N. P. M. Kuin (UCL-MSSL) and A. Amaral-Rogers (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150323C
179 s after the BAT trigger (Amaral-Rogers et al., GCN Circ. 17621
Not found
 
 
).
No optical afterglow consistent with the optical position
(Xu et al. GCN Circ. 17625
Not found
 
 
) 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 first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           179          328          147         >21.5
u_FC               337          587          246         >20.7
white              179        11759         1513         >22.4
v                  669        12698          555         >21.0
b                  594         7661          444         >21.1
u                  337         7541          717         >21.0
w1                 718         7337          432         >21.2
m2                5494         7131          393         >20.6
w2                5084        12665         1279         >22.1

The magnitudes in the table 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).