TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4079
SUBJECT: GRB051008 - Swift UVOT upper limits
DATE:    05/10/09 19:19:43 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aad@mssl.ucl.ac.uk>

A. Breeveld (MSSL-UCL), F. Marshall (GSFC), A. Blustin (MSSL-UCL), M.  
Chester (PSU), L. Angelini (GSFC-JHU)

The UVOT began observing GRB051008 3028 seconds after the BAT trigger  
(GCN 4069, Marshall et al.) at 17:23:49. No afterglow is detected at  
the position of the XRT source (GCN 4073, Perri et al.). The star  
suggested in GCN 4070 (Roming et al.) as a candidate afterglow for GRB  
051008 is now shown not to be associated with the GRB. It is located  
far outside the XRT error box and is not variable in the UVOT  
exposures.
Upper limits for a UVOT detection at the XRT position are given below:

Filter   5sig UL (mags)     T_range(s)         Exp(s)
----------------------------------------------------------------------
  v       18.2            3028     3227         200
  v       18.1            3652     3751         100
  v       20.0            4970    39669        3984
  u       19.1            3442     4056         200
  u       20.4           15631    34555        2461
 w1       19.2            3338     3953         197
 w1       20.6           10753    33885        2865
 m2       19.6            3233     3852         196
 m2       21.3            9847    40339        3361
 w2       19.2            3548     3647         100
 w2       21.4            4064    38762        3277

where T_range is the time range post-trigger over which the summed  
images were accumulated and Exp is the total exposure time of the  
summed image. The magnitude upper limits are not corrected for  
extinction.

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