[vsnet-grb-info 16504] GRB 150428A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17785
SUBJECT: GRB 150428A: Swift/UVOT Upper Limits
DATE:    15/04/29 00:43:45 GMT
FROM:    Margaret Chester at PSU  <chester at swift.psu.edu>

M. M. Chester (PSU) and K. L. Page (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150428A
179 s after the BAT trigger (Page et al., GCN Circ. 17765).  No optical 
afterglow consistent with the enhanced XRT position (Osborne et al. GCN
Circ. 17768) 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 one subsequent exposure are:

Filter         T_start(s)   T_stop(s)      Exp(s)     UL (3-sigma)

white_FC           179         329          147        >20.9
u                 3572        3726          152        >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).