GCN Circular 9517
Subject
GRB 090618: OA behavior from KAIT
Event
Date
2009-06-18T11:21:26Z (16 years ago)
From
Weidong Li at UC Berkeley KAIT/LOSS <weidong@astron.berkeley.edu>
W. Li, D. A. Perley, and A. V. Filippenko, University of California at
Berkeley, on behalf of the KAIT GRB team:
We have analyzed the KAIT observations on GRB 090618 (GCN 9512) as
reported in GCN 9514. Our first 2s unfiltered observation started
at 08:29:44 UT, 75 s after the BAT trigger. The OA as reported in
GCN 9512, 9513, 9514, and 9515 is clearly detected. Subsequent
observations show that the OA declined and reached a bottom at t=92 s,
then brightened and reached a peak at t=120 s. After the peak, the
OA declined as a smooth power-law, with an obvous change of decay
index at t ~ 600 s (from alpha = -1.08 +/- 0.05 to -0.70 +/- 0.02).
Selected photometry, all unfiltered calibrated to the R band via USNO B1:
t_mid(seconds) exp(s) mag mag_err
---------------------------------------
76 2.0 13.61 0.03
92 2.0 13.99 0.04
117 2.0 13.50 0.03
237 20.0 14.02 0.02
436 20.0 14.73 0.02
729 20.0 15.26 0.02
2601 20.0 16.22 0.02
7329 120.0 17.02 0.03