GCN Circular 8452
Subject
GRB 081029, SMARTS optical/IR afterglow observations
Date
2008-10-29T23:19:48Z (16 years ago)
From
Bethany Cobb at UC Berkeley <bcobb@astro.berkeley.edu>
B. E. Cobb (UC Berkeley) reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained
optical/IR imaging of the error region of GRB 081029 (GCN 8435, Sakamoto
et al.) at three epochs with mid-exposure times of 2008-10-29 04:18 UT
(2.57 hrs post-burst), 04:50 UT (3.10 hrs post-burst) and 05:21 UT (3.62
post-burst). At each epoch, several dithered images were obtained in each
filter, with total summed exposure times of 180s in each of BRIJK and 120s
in each of H and V.
The GRB afterglow (e.g. GCN 8436, Rykoff et al. and GCN 8437, Clemens et
al.) is detected in all our filters:
filter 2.57 hrs 3.10 hrs 3.62 hrs
B 19.69+/-0.04 19.85+/-0.04 20.00+/-0.05
V 18.26+/-0.03 18.38+/-0.03 18.57+/-0.04
R 17.32+/-0.02 17.50+/-0.02 17.66+/-0.02
I 16.79+/-0.03 16.94+/-0.03 17.15+/-0.03
J 15.83+/-0.08 16.02+/-0.08 16.03+/-0.08
H 15.00+/-0.08 15.13+/-0.08 15.32+/-0.08
K 14.25+/-0.08 14.35+/-0.08 14.60+/-0.08
These preliminary magnitudes are calibrated using Landolt standard stars
in the optical and 2MASS stars in the IR.
Between 2.57 hrs and 3.62 hours post-burst, the afterglow decays with an
approximate optical decay rate of alpha~-0.9 (where afterglow flux
is proportional to t^alpha).