[vsnet-grb-info 19232] GRB 170318B: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20919
SUBJECT: GRB 170318B: Swift/UVOT Upper Limits
DATE:    17/03/19 08:56:36 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and A. Cholden-Brown (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170318B
84 s after the BAT trigger (Cholden-Brown et al., GCN Circ. 20908).
No optical afterglow consistent with the XRT position (Goad et al. GCN 
Circ. 20910) 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            84          234          147         >20.4
u_FC               296          546          246         >19.8
white               84         6145          530         >21.0
v                  626         6557          432         >19.4
b                  552         5940          236         >20.0
u                  296         7172          659         >20.2
w1                 675         6967          432         >19.9
m2                5123         5323          197         >19.3
w2                 601         6352          216         >19.6

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 4.51 in the direction of the 
burst (Schlegel et al. 1998).