TITLE:   GCN CIRCULAR
NUMBER:  8567
SUBJECT: GRB 081127: Swift/UVOT Upper Limits
DATE:    08/11/27 18:03:49 GMT
FROM:    Stephen Holland at USRA/NASA/GSFC/SSC  <sholland@milkyway.gsfc.nasa.gov>

S. T. Holland (CRESST/GSFC/USRA) and J. Mao (INAF-OAB) report on the
behalf of the Swift UVOT team:

       The Swift/UVOT observed the field of GRB 081127 starting 113 s
after the BAT trigger (Mao, et al. 2008, GCN Circ. 8560).  Settled
exposures started at T+131 s.  We do not find any new source, relative
to the DSS or 2MASS, or any variable source inside the UVOT-enhanced
XRT error circle (Beardmore, et al. 2008, GCN Circ. 8565).
Preliminary 3-sigma upper limits for detecting a source in the white
finding chart, and the co-added images, using a 2.5 arcsecond radius
circular aperture, are

Filter   T_start   T_stop   Exp(s)     Mag
------------------------------------------
  white       130      380      147   >21.3

     v        365   18,799     1473   >21.0
     b        466     7263      568   >21.4
     u        440   13,713     1246   >21.4
   uvw1       415   13,011     1276   >21.6
   uvm2       389   19,496     2004   >21.8
   uvw2       341   17,885     1473   >21.8
  white       490     7468      714   >22.2
------------------------------------------

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.09 mag (Schlegel, et al., 1998, ApJS, 500,
525).  All photometry is on the UVOT photometry system described in
Poole et al. (2008, MNRAS, 383, 627).

      The B = 13.15 mag USNO-B1.0 star 0968-0627697 is located
approximately 4 arcsec north of the XRT position.  UVOT photometry at
the location of the X-ray source is contaminated by this star.