TITLE:   GCN CIRCULAR
NUMBER:  18384
SUBJECT: GRB 151001B: Swift/UVOT Upper Limits
DATE:    15/10/02 18:50:46 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and H. A. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151001B 
148 s after the BAT trigger (Krimm et al., GCN Circ. 18374).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 18377) 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           148          298          147         >20.6
white              148         6765          805         >21.8
u_FC               307          557          246         >19.9
v                  636         7175          529         >20.2
b                  563         6561          333         >20.9
u                  307        11107          685         >20.7
w1                 686         7585          510         >20.2
m2                 661         7380          529         >20.2
w2                 613         6970          529         >20.6

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 1.71 in the direction of the 
burst (Schlegel et al. 1998).