[vsnet-grb-info 2913] GRB 060206: SOAR Detections

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4750
SUBJECT: GRB 060206: SOAR Detections
DATE:    06/02/12 03:18:22 GMT
FROM:    Aaron LaCluyze at U.North Carolina  <lacluyze at physics.unc.edu>

A. LaCluyze, M. Nysewander, J. Haislip, A. de Oliveira, D. Reichart, J.
Santos, A. Alvarez, S. Heathcote, J. C. Clemens, and A. Trotter report on
behalf of the UNC team of the FUN GRB collaboration:

We observed the localization of GRB 060206 (Morris et al., GCN 4682) with
4.1m SOAR at CTIO in VRI beginning 50.8 hours after the burst.

We detect the afterglow (Fynbo et al., GCN 4683) at I = 20.70 +/- 0.04 mag
at an effective time of 51.3 hours after the burst (calibrated to six SDSS
stars; Cool et al., GCN 4695; using the transformation equations of Smith
et al. 2002.)

A more careful analysis of PROMPT's I-band detection from the night before
(Kirschbrown et al., GCN 4712) yeilds I = 19.17 +/- 0.18 mag at an
effective time of 27.0 hours after the burst.  This implies a temporal
index of -2.20 +/- 0.26 between 27.0 and 51.3 hours after the burst, which
is significantly steeper than the temporal index that we measured with
PROMPT on the first night (-1.0; Haislip et al., GCN 4709)

This suggests that the jet is breaking, and at a significantly earlier time
than estimated by Palmer et al. (GCN 4697).

Continued monitoring is encouraged.