TITLE:   GCN CIRCULAR
NUMBER:  10721
SUBJECT: GRB 100504A: Swift/UVOT Observations
DATE:    10/05/05 21:46:28 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <siegel@astro.psu.edu>

M. H. Siegel (PSU) and J. Mao (INAF-OAB) report on behalf
of the Swift/UVOT team.

The Swift/UVOT began settled observations of the field of
GRB 100504A 72s after the BAT trigger (Mao et al.,
GCN Circ. 10712).  Data summed from the first and second orbits
do not reveal a source at the enhanced position of the X-ray
afterglow (Mao et al., GCN Circ. 10713).

The 3-sigma upper limits for the finding chart (fc) and
summed exposures are reported below:

FILTER     T_start(s)  T_stop    Exposure     Mag/3UL
========================================================
white fc      72        222        147        >20.39
white         73       1705        391        >20.91
v            614       1755        136        >18.54
b            713       1680         97        >19.35
u           1463       1816         45        >18.43
uvw1         836       1804         97        >18.92
uvw2         762       1037         38        >18.43
=======================================================

The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E_{B-V} = 0.87 (Schlegel et al.,
1998, ApJS, 500, 525). The photometry is on the UVOT photometric
system described in Poole et al. (2008, MNRAS, 383, 627).