TITLE:   GCN CIRCULAR
NUMBER:  18405
SUBJECT: GRB 151006A: Swift/UVOT Upper Limits
DATE:    15/10/06 19:03:04 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151006A 36 
s after the BAT trigger (Kocevski et al., GCN Circ. 18398).
No optical afterglow consistent with the XRT position (Goad et al. GCN 
Circ. 18403) 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            58          208          147         >20.7
u_FC               271          521          246         >19.9
white               58         6351          520         >21.4
v                   36         6754          437         >19.8
b                  527         6146          236         >20.3
u                  271         5941          442         >20.3
w1                5537         5736          197         >19.8
m2                 625         5531          235         >19.7
w2                 577         6557          432         >20.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.24 in the direction of the 
burst (Schlegel et al. 1998).