[vsnet-grb-info 7935] GRB 090530: Early RAPTOR Optical Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9478
SUBJECT: GRB 090530: Early RAPTOR Optical Observations
DATE:    09/06/02 00:37:08 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
353567 (Cannizzo et al., GCN 9438) under fair observing conditions.
Our narrow-field instruments began observing the location at
03:18:37.96 UTC, 19.6 s after the Swift trigger.  We detect the
optical counterpart initially reported by Cannizzo et al. (GCN 9438)
and Flewelling et al. (GCN 9439).  Our first image at T+22.1 seconds
shows the counterpart at R~17.1.  It appears to brighten over the
next minute reaching a peak near R~16.3 and then begins fading in
the manner described by Schady et al. (GCN 9450) and Rossi et al.
(GCN 9458).  Our unfiltered images were calibrated against the
USNO-B1 R-band.  The following table gives selected observations,
not corrected for extinction, from this event.

t-mid(s)    exp(s)     mag     mag-err
--------------------------------------------
22.08        5.0      17.13    0.25
57.90        5.0      16.30    0.10
84.50        5.0      16.60    0.13
133.21      10.0      16.87    0.11
414.65      30.0      17.31    0.09