[vsnet-grb-info 12156] GRB 120729A: Early RAPTOR Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13545
SUBJECT: GRB 120729A: Early RAPTOR Observations
DATE:    12/07/30 21:15:47 GMT
FROM:    James Wren at LANL  <jwren at nis.lanl.gov>

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

The RAPTOR network of robotic optical telescopes responded to Swift trigger
529095 (Ukwatta et al., GCN 13530).  Observations began at 10:56:42.0 UT,
27.9 s after the initial Swift trigger and before the end of the gamma-ray
emitting interval.  Our observations were performed under clear skies with
morning twilight just beginning.  We clearly detect the optical counterpart
(Ukwatta et al., GCN 13530, and Virgili et al., GCN 13531).  We initially
detect the counterpart at a magnitude of 13.2, and at about T+50 s
it begins to fade steadily at a power law index of about 0.9 for the next
1000 seconds.  Our unfiltered magnitudes are calibrated against the USNO-B1
R-band.  The following table gives a sample of some of our observations.
The image mid-points are given relative to the initial BAT trigger time.

t-mid(s)  exp(s)  mag     error
--------------------------------------
30.4      5       13.21   0.01
39.8      5       13.28   0.01
49.2      5       13.35   0.01
118.4     10      14.18   0.01
248.8     10      14.97   0.02
391.8     30      15.36   0.02
817.0     30      16.11   0.06
1071.4    30      16.46   0.11