[vsnet-grb-info 20542] GRB 180411A: Swift/UVOT Upper Limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22638
SUBJECT: GRB 180411A: Swift/UVOT Upper Limit
DATE:    18/04/12 10:53:05 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and Z. Liu (NAOC/U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began observations of the field of GRB 180411A 64 s after 
the BAT trigger (Liu et al., GCN Circ. 22630) with a settling exposure 
in the V filter. The UVOT safety circuit tripped 3.4s into the following 
UV grism exposure, most likely due to the bright star HD223128, 5.08 
arcmin from the burst position.

No optical afterglow consistent with the enhanced XRT position (Gibson 
et al. GCN Circ. 22632) is seen in the 9.3s V settling exposure to a 
preliminary 3-sigma upper limit of 16.8 mag using the UVOT photometric 
system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373).

The magnitude is not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.104 in the direction of the burst
(Schlegel et al. 1998).