TITLE:   GCN CIRCULAR
NUMBER:  7000
SUBJECT: Swift UVOT upper limits
DATE:    07/10/25 19:00:39 GMT
FROM:    Paul Kuin at MSSL  <npkuin@googlemail.com>

N.P.M. Kuin (MSSL/UCL) and C. Pagani (PSU) report on behalf of the
Swift UVOT team:

The Swift/UVOT observed the field of GRB 071025 (found with Swift
BAT, as reported in GCN 6986 of Pagani et al.) beginning 2007-10-25
04:11:11 UT, 137 seconds after the burst trigger time. After a 10 s
settling image in V, a 98 s finding chart exposure in the white filter
was taken, followed by observations in all filters.

No new source was found in any of the UVOT observations inside
the reported position of the Swift XRT error circle (Pagani et al,
GCN 6990, 6998) or the position of the detection of a transient
source in the red bands of which the most accurate was the PARITEL
observation in the J band (J. Bloom, GCN 6989), consistent with
the refined XRT position. We report upper limits at position
RA=23:40:17.078, DEC=+31:46:42.87 (J2000).

The 3-sigma upper limits for detecting a source at the reported position
in the co-added frames as determined are:

Filter   Tstart   Tstop    Exp     Magnitude
            (s)     (s)     (s)    (3-sigma UL)
White       155   16016    1377     22.82
v           137   17760    1319     21.22
b          3968   11968    1194     22.14
u          3760   23536    2085     22.13
uvw1       3552   22704    2164     22.05
uvm2       4784   21808    1082     21.43
uvw2       4368   16928    1279     21.89

The values quoted above are not corrected for the expected Galactic
extinction corresponding to a reddening of E_{B-V} = 0.074 mag in the
direction of the burst (Schlegel et al. 1998).