[vsnet-grb-info 8804] Swift Trigger 381591: Uncatalogued UVOT Source

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10303
SUBJECT: Swift Trigger 381591: Uncatalogued UVOT Source
DATE:    09/12/31 19:18:15 GMT
FROM:    Stephen Holland at USRA/NASA/GSFC/SSC  <Stephen.T.Holland at nasa.gov>

S. T. Holland (CRESST/GSFC/USRA), M. H. Siegel (PSU), and
C. B. Markwardt (CRESST/GSFC/UMD) report on the behalf of the
Swift/UVOT team:

    The Swift/UVOT observed the field of BAT trigger 381591
(Markwardt et al. 2009, GCN Circ. 10301) starting approximately 132 s
after the BAT detection.  We find an uncatalogued source, relative to
the USNO B1.0 and 2MASS point source catalogues, at

    RA =  15:40:18.21 = 235.07592 deg
   Dec = -08:43:31.9  =  -8.72553 deg

with a preliminary error estimate of 1.0 arcsec (radius, 90%
containment).  This is 48 arcsec NW of the centre of the BAT error
circle.  The preliminary u-band magnitude is

Filter     TSTART     TSTOP     EXPOSURE        Mag  Err
--------------------------------------------------------
u             290       472          181       16.2  0.1
--------------------------------------------------------

At present there are insufficient data to tell if this source is
fading.  This source is 6.3 arcsec north of the bright (B = 14 mag)
USNO B1.0 source 0812-0291183.  Due to the lack of an X-ray detection
and the lack of information about the source's variability we can not
make any claim about this source being related to the BAT trigger.

    The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.14 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).