TITLE:   GCN CIRCULAR
NUMBER:  24703
SUBJECT: GRB 190530A: Swift/UVOT Detection
DATE:    19/06/01 03:10:41 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190530A
33.8 ks after the LAT trigger (GCN Circ. 24676). A fading source consistent
with the optical counterpart first reported by Lipunov et al. (GCN Circ.
24680) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
   RA  (J2000) =  08:02:07.70 = 120.53209 (deg.)
   Dec (J2000) = +35:28:46.8  =  35.47968 (deg.)
with an estimated uncertainty of 0.49 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

v                56532        56734          199         18.49 +/- 0.23
b                38334        38490          153         18.06 +/- 0.09
u                38132        38329          194         17.09 +/- 0.06
w1               37734        38128          388         16.89 +/- 0.06
w2               44276        44610          329         17.39 +/- 0.08

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).