TITLE:   GCN CIRCULAR
NUMBER:  23215
SUBJECT: GRB 180905A: Swift/UVOT Upper Limits 
DATE:    18/09/09 19:37:38 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@swift.psu.edu>

M. H. Siegel (PSU) and V. D'Elia (SSDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180905A
154 s after the BAT trigger (D'Elia et al., GCN Circ. 23201).
No optical afterglow consistent with the XRT position
(D'Elia et al. GCN Circ. 23201) is detected in the initial UVOT exposures,
as confirmed by Bootes (Hu et al., GCN Circ. 23208), MITSUME (Niwano
et al., GCN Circ. 23211) and RATIR (Watson et al., GCN Circ. 23212).
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           154          289          133         >20.4
white              154         6385          373         >21.1
v                 5316         5515          197         >19.1
b                 4700         6335          393         >20.5
u                 4495         6130          393         >20.3
w1                5726         5925          197         >19.6
m2                5520         5720          197         >19.8
w2                5111         5311          197         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.60 in the direction of the burst
(Schlegel et al. 1998).