GCN Circular 17673

N. P. M. 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 150403A
85 s after the BAT trigger (Lien et al., GCN Circ. 17665
Not found
 
 
).    A source
consistent with the XRT position (Beardmore et al. GCN Circ. 17666
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  20:46:01.15 = 311.50479 (deg.)
    Dec (J2000) = -62:42:41.0  = -62.71139 (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               85          235          147         14.89 +/- 0.02
v                  627          647           20         16.49 +/- 0.13
b                  553          573           20         16.65 +/- 0.08
u                  298          547          246         16.14 +/- 0.03
w1                 676         5286          294         19.68 +/- 0.21
m2                6317        23414         1178        >22.2
w2                5907         7536          387        >20.6

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).