TITLE: GCN CIRCULAR NUMBER: 12803 SUBJECT: GRB111225A: RAPTOR Early Detection of the Optical Counterpart DATE: 12/01/04 01:15:03 GMT FROM: James Wren at LANL J. Wren, W. T. Vestrand, P. Wozniak, and H. Davis of Los Alamos National Laboratory report: The RAPTOR network of robotic optical telescopes responded to Swift trigger 510341 (GRB 111225A, Siegel et al., GCN 12720). Unfiltered observations of the source location began at 03:51:27.2 UTC, 49.4 seconds after the BAT trigger time. The initial short exposures during the first two mintues of our response sequence do not clearly show the counterpart. However, stacking those images, 8 5-second exposures taken between 03:51:37.6 UTC and 03:52.46.0 UTC, gives a 5-sigma detection at counterpart location (Klotz et al., GCN 12722, and Updike et al., GCN 12723). Based on comparison to the USNO-B1 R-band, the measured brightness is R~18.7 +\- 0.3 at a t-mid of 03:52:12 UTC, 94 seconds after the Swift BAT trigger.