TITLE:   GCN CIRCULAR
NUMBER:  22893
SUBJECT: GRB 180704A: Swift/UVOT Upper Limits
DATE:    18/07/04 13:31:43 GMT
FROM:    Sam Emery at MSSL-UCL  <samuel.emery.15@ucl.ac.uk>

S.W.K. Emery (UCL-MSSL) and E. Sonbas (Adiyaman Univ.) and
A. A. Breeveld (UCL-MSSL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180704A
3255 s after the BAT trigger (Sonbas et al., GCN Circ. 22885).
No optical afterglow consistent with the XRT position
(Evans et al. GCN Circ. 22890)
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
exposures are:

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

white             3255         5455          537         >20.8
v                 4233        10567         1082         >19.8
b                 3618         5253          393         >19.9
u                 3413         5048          393         >19.6
uvw1                4643         4843          197         >19.2
uvm2                4438        11190          804         >20.3
uvw2                4028         9654         1082         >20.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.87 in the direction of the burst
(Schlegel et al. 1998).