[vsnet-grb-info 12454] GRB 120927A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13829
SUBJECT: GRB 120927A: Swift/UVOT Upper Limits 
DATE:    12/09/29 15:02:02 GMT
FROM:    Stefan Immler at NASA/GSFC  <stefan.m.immler at nasa.gov>

S. Immler (NASA/CRESST/GSFC) and A. Maselli (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 120927A
158 s after the BAT trigger (Maselli et al., GCN Circ. 13822).
No optical afterglow consistent with the enhanced XRT position
(Beardmore et al. GCN Circ. 13824) 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) and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           158          308          147         >20.3
u_FC               317          567          246         >19.5
white              158         6331          580         >21.0
v                  648         6625          317         >19.1
b                  572         6127          432         >20.1
u                  317         5921          659         >20.2
w1                 697         5717          413         >19.6
m2                 672         5511          225         >19.6
w2                 623         6537          432         >20.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).