TITLE:   GCN CIRCULAR
NUMBER:  23834
SUBJECT: GRB 190202A: Swift/UVOT Detection
DATE:    19/02/02 13:00:54 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (UCL/MSSL) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190202A
173 s after the BAT trigger (Lien et al., GCN Circ. 23830). The source
was also observed in R (Novichonok et al., GCN Circ. 23831). A source
consistent with the XRT position  (Evans et al. GCN Circ. 23832)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  11:06:00.63 = 166.50261 (deg.)
    Dec (J2000) = +09:22:36.7  =   9.37687 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits 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              173          299          124         16.02 +/- 0.03
v                 1613         2153           78         17.94 +/- 0.18
b                 1711         1903           39         18.38 +/- 0.16
u                 1686         2054           58         18.20 +/- 0.17
w1                1662         2376           97        >18.5

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).