GCN Circular 18531

S. R. Oates (IAA-CSIC/UCL-MSSL) and T. N. Ukwatta (LANL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151029A
92 s after the BAT trigger (Ukwatta et al., GCN Circ. 18522
Not found
 
 
).
A source consistent with the XRT position (Beardmore et al., GCN Circ. 18526
Not found
 
 
)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
  RA  (J2000) =  02:34:06.72 =  38.52799 (deg.)
  Dec (J2000) = -35:23:08.6  = -35.38573 (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               92          242          147         16.98 +/- 0.03
v                  634          653           19         17.66 +/- 0.32
b                  560          752           39         19.24 +/- 0.33
u                  304          554          246         17.35 +/- 0.06
w1                 683          703           19        >17.98
m2                 658          850           39        >18.17
w2                 609          802           39        >18.64

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).