TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3115
SUBJECT: GRB 050318: Swift/UVOT detection of afterglow emission
DATE:    05/03/19 02:05:06 GMT
FROM:    Martin Still at NASA/GSFC Swift SSC  <Martin.Still@gsfc.nasa.gov>

K. McGowan, M. De Pasquale (MSSL), P. Boyd (GSFC/UMBC),
S. T.  Holland, M. Still (GSFC/USRA), W. Landsman (GSFC),
S. Hunsberger (PSU), A.  Breeveld (MSSL), P. Roming (PSU), K. Mason,
P. Schady (MSSL), M.  Ivanushkina (PSU), T. Poole (MSSL), C. Gronwall
(PSU), A. Blustin (MSSL), P. Brown, S. Rosen, S. Koch (PSU), M. Carter,
H. Huckle (MSSL), P. Broos (PSU), T.  Kennedy, P. Smith, B. Hancock
(MSSL), H. Krimm (GSFC/USRA), J. Nousek (PSU), N. Gehrels (GSFC), on
behalf of the Swift UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began
settled observations of the field of GRB 050318 (Krimm
et al; GCN 3111) at 16:39:16 UT, 3,279s after the BAT
trigger.  The delay in acquiring the target was caused
by an earth limb constraint. The first data taken after
spacecraft settling was a 100s V image, sent directly to
the ground through the TDRSS system, with pixel binning
of 8x8 to reduce telemetry. Binned pixel sizes are 4x4
arcsec and the field of view is 5.3x5.3 arcmin.
Mid-exposure time was 3,329s after the trigger. A
comparison against the Digitized Sky Survey reveals a
new source inside the BAT and XRT (Nousek et al; GCN
3113) error circles at:

RA = 03 18 51.2(1) Dec = -46 23 43(2) J2000

and consistent with the R-band detection of Mulchaey &
Berger (GCN 3114) The V band magnitude is V = 18.4(3).
The magnitude is based on ground data and will require
confirmation by flight calibration.

The full-resolution version of this image will be
transmitted to the ground during the next Malindi pass
providing an improved position.