GCN Circular 19333

F. E. Marshall (NASA/GSFC) 
reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160422A
32624 s after the LAT trigger (Yassine et al. GCN Circ. 19329
Not found
 
 
).
A candidate optical afterglow
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  02:48:22.79 =  42.09497 (deg.)
    Dec (J2000) = -57:52:30.4  = -57.87511 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

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

white            33427        34064          627         19.71 +/- 0.07
u                32624        33420          783         19.05 +/- 0.11

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).

[GCN OPS NOTE(25apr16), Per author's request, the LAT reference was corrected.]