TITLE:   GCN CIRCULAR
NUMBER:  4167
SUBJECT: GRB051021B: Swift/UVOT Upper limits
DATE:    05/10/26 20:33:52 GMT
FROM:    Peter Brown at PSU  <pbrown@astro.psu.edu>

P. J. Brown (PSU), A. Retter (PSU), F. Marshall (GSFC),
A. Smale (NASA HQ), N. Gehrels (GSFC)
on behalf of the Swift/UVOT team report:

Swift-UVOT observed the field of GRB 051021B
(BAT Trigger=160672; Retter et al. GCN 4126)
starting at 2005-10-21 23:33:11, 78 seconds after the burst.

No source was detected within the XRT error circle
(Racusin et al GCN 4128) during the first 200 second image
(Tmid=178 seconds after the burst) down to a 3 sigma
limiting magnitude of V=19.  Using summed images,
we also did not detect a source in any of our 6 filters
down to the following 3-sigma magnitude upper limits:

Filter  T_range(sec)   Exp(sec)  3sigUL
V       78-19380       1779      19.9
B       444-17793      1634      21.1
U       390-13591      961       19.9
W1      336-12417      1199      19.5
M2      282-12005      1199      19.6
W2      553-18702      1940      20.0
White   498-926        100       19.5

Where T_range is time post-trigger.

We note that this position is near the galactic
plane, so the extinction and background in this line of sight are high.