GCN Circular 7808

N. P. M. Kuin (MSSL/UCL), and V. Mangano (INAF-IASFPA), report on behalf
of the Swift UVOT team

The Swift UltraViolet/Optical Telescope (UVOT) began observations
of GRB 080603A, on June 3, 2008, at  19:39:07 UT,  63 seconds after
the initial Swift BAT trigger (Mangano et al., GCN Circ. 7794
Not found
 
 
)..

The refined uvot position is

 RA  = 11:46:07.66 = 176.5316
 DEC =+68:03:39.99 = 68.061105

with an error or 0.3".

The first finding chart in the wh filter has problems due to the
brightness of the image, and needs detailed analysis. We start
our report with the second finding chart.

The magnitudes with 1-sigma errors for GRB080603B are given below
for the initial observation sequence.

Filter Tstart(s) Tstop(s) Exp(s) Magnitude

v       187.8      393.1    202    16.48 +/- 0.06
uvm2   5778.0     5977.8    197    > 19.51 (3-sigma UL)
uvw1   5983.9     6183.7    197    20.02 +/- 0.56
u      6188.8     6388.6    197    18.80 +/- 0.23
b      6395.3    12274.3    643    19.34 +/- 0.14

The absence of a detection in the uvm2 filter is consitent with
the reported redshift of 2.69 (Fynbo et al., GCN Circ. 7797
Not found
 
 
).

Magnitude variation in the b observations shor evidence
of flaring or rebrightening..

The values quoted above are on the UVOT Photometric System
(Poole et al, 2008, MNRAS 383,627). They are not corrected for the
expected galactic reddening of E(B-V) = 0.013 in the direction of
the burst (Schlegel et al. 1998).