GCN Circular 4300
GRB 051117A: Swift/UVOT Detection of an Afterglow S. T. Holland (GSFC/USRA), D. Band (GSFC), K. Mason (PPARC), F. Marshall (GSFC), & N. Gehrels (GSFC) on behalf of the Swift/UVOT team report: The Swift/UVOT began observing the field of GRB 051117A (BAT Trigger 163268; Band et al. 2005, GCN Circular 4280) at 2005-11-17T10:53:10, 111 seconds after the burst. We detect a fading source corresponding to the UVOT source in Band et al. (2005, GCN Circular 4280). The refined coordinates of this source are: RA(J2000) = 15:13:39.09 Dec(J2000) = +30:52:12.7 with a positional uncertainty of +/-0.5 arcsec (1-sigma). The transient has V = 20.01 +/- 0.46 (1-sigma, statistical) in a 200 s exposure starting at 110 seconds after the BAT trigger. This value supersedes the approximate magnitude given in Band, et al. (2005, GCN Circular 4280). This magnitude has not been corrected for Galactic extinction. The magnitude in the UVOT White filter is 19.19 +/- 0.16 (1-sigma, statistical) in a 50 s, exposure starting 531 s after the BAT trigger. The source has faded to a White magnitude of approximately 21.5 by 3.5 days after the burst. There is weak evidence that the source is extended, so this may represent the luminosity of the host galaxy of GRB 051117A.