[vsnet-grb-info 8451] GRB 090929B: RAPTOR Discovery of Optical Counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9967
SUBJECT: GRB 090929B: RAPTOR Discovery of Optical Counterpart
DATE:    09/09/29 16:46:34 GMT
FROM:    James Wren at LANL  <jwren at nis.lanl.gov>

J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis, B. Norman
of Los Alamos National Laboratory report:

The RAPTOR telescope system responded to Swift trigger
371050 (Pagani et al., GCN 9963) under good observing conditions.
Our narrow-field instruments began observing the location at
10:20:53.37 UTC, 11.77 minutes after the initial BAT trigger.
Our initial images show an R~16.8 optical counterpart at the enhanced
XRT location (Page et al., GCN 9965).  The object fades steadily
reaching R~18.0 at 10:50 UTC.  Our unfiltered images were calibrated
against the USNO-B1 R-band. Unfortunately, an 11th magnitude star is
only 19 arcseconds away, limiting our photometric accuracy.  Further
analysis is ongoing.