TITLE:   GCN CIRCULAR
NUMBER:  16772
SUBJECT: GRB 140903A: Swift/UVOT Upper Limits
DATE:    14/09/04 10:35:34 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and J. R. Cummings (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 140903A 76 
s after the BAT trigger (Cummings et al., GCN Circ. 16763).
No optical afterglow consistent with the XRT position (De Pasquale et 
al. GCN Circ. 16767) or optical position given by Cenko et al. (GCN 
Circ. 16770), is detected in the initial UVOT exposures. The analysis is 
complicated by the wings of the bright star mentioned by Capone et al. 
(GCN Circ. 16767), and thus the upper limits should be treated with caution.
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            77          227          147         >20.01
u_FC               289          539          246         >17.4
white               77        17449          944         >21.0
v                  618        29425         1322         >18.9
b                  544        17228         1376         >20.0
u                  289        23404         1138         >18.2
w1                1097        22967         1121         >18.4
m2                 643         6613          255         >18.8
w2                5562        28728         1918         >18.6

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.03 in the direction of the 
burst (Schlegel et al. 1998).