TITLE:   GCN CIRCULAR
NUMBER:  10432
SUBJECT: GRB 100219A: Swift/UVOT Detection of a Source near the XRT Position 
DATE:    10/02/19 17:29:24 GMT
FROM:    Stephen Holland at USRA/NASA/GSFC/SSC  <Stephen.T.Holland@nasa.gov>

S. T. Holland (CRESST/GSFC/USRA),
N. P. M. Kuin (UCL-MSSL), and
A. Rowlinson (U Leicester)
report on the behalf of the Swift/UVOT team:

       The Swift/UVOT observed the field of GRB 100219A (Rowlinson et
al. 2010, GCN Circ. 10430) starting 183 s after the BAT detection.  We
do not detect any source inside the XRT error circle, but we do detect
a source 3.8 arcsec north of the centre of the 2.1 arcsec XRT error
circle.  This source is not present in the SDSS DR7, USNO B1.0, or
2MASS point source catalogues.  It is at the detection limit of the
DSS, so it is unclear if this is a new source.  The preliminary UVOT
position is

     RA (J2000)  10:16:48.54  =  154.20225 (deg)
    Dec (J2000) -12:33:57.9   =  -12.56608 (deg)

with an estimated uncertainty of 1.0 arcsec (radius, 90% confidence,
statistical + systematic).

Preliminary magnitudes for this source are

Filter   TSTART    TSTOP   Exposure      Mag   Err   Sigma
---------------------------------------------------------------
white       183      333        150    20.70  0.34     3.2
white       875     1025        150   >20.9            3-sigma UL
u           341      591        250    21.00  0.56     2.0
---------------------------------------------------------------

It is not clear if this source is fading, or if it is associated with
GRB 100219A.

     The quoted magnitudes have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.08 mag (Schlegel et al., 1998, ApJS, 500,
525).  All photometry is on the UVOT photometry system described in
Poole et al. (2008, MNRAS, 383, 627).