TITLE:   GCN CIRCULAR
NUMBER:  9432
SUBJECT: GRB 090529: Preliminary Swift/UVOT Upper Limit
DATE:    09/05/29 17:12:13 GMT
FROM:    Stephen Holland at USRA/NASA/GSFC/SSC  <sholland@milkyway.gsfc.nasa.gov>

S. T. Holland (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC),
P. Schady (MSSL-UCL), and T. Sakamoto (NASA/UMBC) report on the behalf
of the Swift UVOT team:

      The Swift/UVOT took a 150 s exposure of the field of GRB 090529
with its white filter starting 204 s after the BAT trigger (Sakamoto,
et al., 2009, GCN Circ. 9430).  The preliminary 3-sigma upper limit at
the XRT position is white > 20.3.  This upper limit has not been
corrected for the expected Galactic extinction along the line of sight
corresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel, et al.,
1998, ApJS, 500, 525).  The photometry is on the UVOT photometric
system described in Poole et al. (2008, MNRAS, 383, 627).

      The non-detection in the white filter at 204 s, combined with the
observation at 28 minutes of R ~ 19.4 (Xin, et al., 2009, GCN Circ.
9431) implies either that this afterglow is unusually red, or that it
has brightened during the first half hour after the BAT trigger.  Such
a long brightening would be highly unusual (Oates, et al., 2009,
MNRAS, 395, 450).