[vsnet-grb-info 11391] GRB111225A: RAPTOR Early Detection of the Optical Counterpart

[GCN Circulars]

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  <jwren at nis.lanl.gov>

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.