GCN Circular 10111
Subject
GRB 091029, SMARTS optical/IR afterglow observations
Date
2009-10-29T23:30:19Z (15 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 091029 (GCN 10097, Grupe et
al.) with a mid-exposure time of 50 minutes post-burst (2009-10-29 04:43
UT). Total summed exposure times amounted to 36 minutes in I and 30
minutes in J. Imaging was done under poor (2.5") seeing conditions.
The afterglow of GRB 091029 (e.g. GCN 10097, Grupe et al.; GCN 10098,
Filgas et al.; GCN 10099, LaCluyze et al.) is detected in our images.
Preliminary comparison to USNO-B1.0 stars in I and 2MASS stars in J
indicates the following afterglow magnitudes:
time post-burst I mag J mag
50 minutes 17.9+/-0.1 17.6+/-0.1
In individual I-band images, the afterglow fades by ~0.4 magnitudes
between 30 and 69 minutes post-burst. During this time, the afterglow
exhibits a shallow decay rate of alpha ~ -0.4+/-0.1 (where afterglow flux
is proportional to t^alpha), which is consistent with the decay rate
measured by LaCluyze et al. (GCN 10099).