TITLE:   GCN CIRCULAR
NUMBER:  8069
SUBJECT: GRB 080804: Swift/UVOT Refined Analysis
DATE:    08/08/05 18:29:58 GMT
FROM:    Paul Kuin at MSSL  <npkuin@googlemail.com>

N. P. M. Kuin (MSSL/UCL), and J. L. Racusin (PSU), report
on behalf of the Swift UVOT team

The Swift UltraViolet/Optical Telescope (UVOT) began observations
of GRB 080804, on August 4, 2008, at  23:21:45 UT, 91 seconds after
the initial Swift BAT trigger (Racusin et al., GCN Circ. 8057), and
started the finding chart exposure in the white filter at 111
seconds after the trigger.

The refined uvot position of GRB080804 is RA=0328.66750 Dec=-53.18461
deg.(= 21:54:40.2 -53:11:04.6), with an accuracy of 0.4", consistent
with the positions reported in GCN Circ. 8056 (Rujokaparn et al.),
8057 (Racusin et al.) and 8066 (Beardmore et al.).

The magnitudes with 1-sigma errors for GRB080804 are given below
for the initial observation sequence.

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

wh      111        210     98.2    16.83 +/- 0.03
wh      711        720      9.6    18.3  +/- 0.16
v       217        616    393.5    17.17 +/- 0.05
v       752        771     19.4    17.85 +/- 0.30
uvm2    623        642     19.5   >17.6  (3 sigma UL)
uvw1    648        667     19.4   >18.2  (3 sigma UL)
b       697        706      9.6    18.1  +/- 0.27
u       672        691     19.4    17.4  +/- 0.17
uvw2    727        746     19.5   >18.2  (3 sigma UL)

uvw1    648       7442    529.3    20.9  +/- 0.4
uvm2    623       7237    529.4   >20.8  (3 sigma UL)
uvw2    727       6827   1179.5   >21.8  (3 sigma UL)

The upper limits in uvw2, uvm2, and weak detection in uvw1 are
consistent with the reported redshift of z=2.2045 by Thoene
et al. (GCN Circ. 8058).

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) = 0.016 in the direction of
the burst (Schlegel et al. 1998).