TITLE:   GCN CIRCULAR
NUMBER:  6006
SUBJECT: GRB070107 Swift/UVOT Observations of a Fading Optical Afterglow
DATE:    07/01/10 17:04:52 GMT
FROM:    Padi Boyd at GSFC  <padi@milkyway.gsfc.nasa.gov>

GRB 070107: UVOT Observations of a Fading Optical Afterglow

P. T. Boyd and F. E. Marshall (NASA/GSFC) report on behalf of the Swift team:

UVOT observed the field of GRB 070107 (Stamatikos et al. GCN Circ. 5999).
The complete data set through T=117,471s now available clearly shows a
fading source at the position reported by Boyd et al. (GCN Circ 6002).
This afterglow candidate is visible at early times in the White and
V filters, and probably also in the U filter.

The table below gives the measured magnitudes after correcting for
flux in the source aperture due to the bright (V=15.9 mag) nearby
star. Reported significance levels were calculated based on rates
in the source region, while magnitude errors include the contribution
from aperture correction.

Filter  TSTART  Exposure        Mag     Error   Significance

White   181     98              19.5    0.3        5.6
White   5355    197             20.5    0.3        3.5
V       286     393             19.2    0.3        3.9
V       971     393             19.8    0.4        2.0
U       29220   590             20.6    0.4        2.8
B       5151	197             20.7  	(3sigma UL)
W1      6174	197             20.0    (3sigma UL)
M2      16718	886             20.5    (3sigma UL)
W2      22501	886             20.8 	(3sigma UL)

These magnitudes have not been corrected for the large and unreliable
Galactic extinction at this position.