GCN Circular 6238

N.P.M. Kuin (MSSL-UCL), D. Grupe (PSU), P. Brown (PSU) report
on behalf of the Swift/UVOT team:

The Swift/UVOT began taking data in the field of GRB070330 54s after the BAT 
trigger (Grupe et al., GCN 6232
Not found
 
 
). The afterglow is only detected in the first 
UVOT V exposure, with a magnitude of V=18.69+/-0.24, after which the afterglow 
had decayed below the UVOT detection threshold, suggesting a decay rate of 
alpha_V > 0.8. The refined UVOT afterglow position is
RA (J2000)  = 17:58:09.98 (269.5426)
Dec (J2000) = -63:47:34.80 (-63.7930)
We note that the refined position is 0.5" away from the preliminary UVOT 
position reported in GCN 6232
Not found
 
 
. The photometry results are given below for the 5 
UVOT filters in which observations were made. Due to the presence of a bright 
star no observations could be obtained in the UVW2 and white filters.

Filter  Mid_T(s)   Exp(s)  Mag
V       266        393     18.69+/-0.24
V       33978      1632    > 21.45 (3-sigma upper limit)
M2      25521      2814    > 18.35 (3-sigma upper limit)    `
W1      20282      1998    > 18.36 (3-sigma upper limit)
U       25521      2814    > 21.60 (3-sigma upper limit)
B       30318      3305    > 18.15 (3-sigma upper limit)

Mid_T is the weighted mid time of the exposure since the BAT trigger. These 
magnitudes are not corrected for the expected reddening of E(B-V)=0.063.

For the time being it is not possible to provide a redshift given the low 
signal-to-noise ratio of the data. Further analysis is ongoing. A high (~4) 
redshift is possible and we encourage further ground follow-up.

[GCN OPS NOte(25aug07): Per UVOT Team request, the Mid_T value
for the first V exposure ws changed from 462 to 266. Acknowledgements
to F. Marshall.]