[vsnet-grb-info 22234] GRB 190427A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24333
SUBJECT: GRB 190427A: Swift/UVOT Upper Limits
DATE:    19/04/28 20:09:21 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

N. P. M. Kuin (UCL-MSSL) and A. Tohuvavohu (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 190427A
3737 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 24261).
No optical afterglow consistent with the BAT position (Ukwatta et al.,
GCN Circ. 24330) 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 initial exposures are:

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

u                 3737         3936          197         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.06 in the direction of the burst
(Schlegel et al. 1998).