[vsnet-grb-info 17168] GRB 151027B: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18517
SUBJECT: GRB 151027B: Swift/UVOT Upper Limits
DATE:    15/10/28 15:45:21 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and T. N. Ukwatta (LANL) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151027B 
210 s after the BAT trigger (Ukwatta et al., GCN Circ. 18499).
No optical afterglow consistent with the XRT position (Osborne et al. 
GCN Circ. 18504) 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           210          359          147         >20.0
white              210         4545          344         >20.5
v                  366         4956          216         >18.8
b                 4141         5737          354         >20.6
u                 3935         5571          393         >20.4
w1                 415         5366          397         >20.4
m2                4961         5161          197         >19.1
w2                4551         4751          197         >19.9

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.25 in the direction of the 
burst (Schlegel et al. 1998).