[vsnet-grb-info 14809] GRB140419A: UVOT detects fading afterglow in white but not in u filter

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16123
SUBJECT: GRB140419A: UVOT detects fading afterglow in white but not in u filter
DATE:    14/04/19 07:56:22 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

NPM Kuin (MSSL-UCL), and F. E. Marshall (NASA/GSFC) report on behalf of
the Swift Team:

UVOT started observing GRB 140419A starting 96 seconds after the BAT
trigger.
The initial finding chart exposures with the White and U filter show a
fading source in the white filter which we identify with the afterglow:

The estimated magnitudes are as follows:

filter starttime endtime magnitude error
wh      96         246    16.01    0.06
u      308         558    >19.6
wh     862        1012    17.96    0.09.

The source is not seen in the u filter, which suggests a redshift larger
then
2.8.

No correction has been made for the expected extinction corresponding to
E(B-V) of 0.03.