TITLE:   GCN CIRCULAR
NUMBER:  22627
SUBJECT: GRB 180410A: Swift/UVOT Upper Limits
DATE:    18/04/10 18:18:04 GMT
FROM:    Frank Marshall at Swift/UVOT  <marshall@milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180410A
179 s after the BAT trigger (Gropp et al., GCN Circ. 22620).
No optical afterglow consistent with the enhanced XRT position
(Evans et al. GCN Circ. 22622)
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          329          147         >20.6
u_FC               338          587          246         >20.0
white              179         2068          450         >20.9
v                  669         1943          156         >19.2
b                  594         2043          156         >20.1
u                  338         2017          382         >20.4
w1                 718         1993          136         >20.1
m2                 693         1968          136         >20.3
w2                 644         2093          175         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.92 in the direction of the burst
(Schlegel et al. 1998).