TITLE:   GCN CIRCULAR
NUMBER:  19390
SUBJECT: GRB 160504A: Swift/UVOT Upper Limits
DATE:    16/05/05 18:34:55 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and D. Malesani (DARK/NBI)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160504A
99 s after the BAT trigger (Malesani et al., GCN Circ. 19382).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 19386)
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)             99          249          147         >20.8
white               99        11822         1316         >21.7
v                  587        16542         1317         >20.2
b                  513        10910         1145         >21.5
u (fc)                257          507          246         >20.4
u                  257         6616          678         >21.2
w1                 636         6411          432         >20.4
m2                4571        17443         1275         >21.0
w2                 735        12387          963         >21.7

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).