TITLE:   GCN CIRCULAR
NUMBER:  25257
SUBJECT: GRB 190731A: Swift/UVOT Upper Limits
DATE:    19/08/02 13:47:54 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

S. R. Oates (U.Warwick) and S. Dichiara (UMCP/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190731A
33372 s after the LAT trigger (Ohno et al., GCN Circ. 25244).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ. 25251) 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

v                39548        40152          590         >20.0
b                45350        45715          355         >20.7
w2               33372        33977          596         >20.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.13 in the direction of the burst
(Schlegel et al. 1998).