GCN Circular 5878
Subject
GRB 061121, SMARTS optical/IR observations
Event
Date
2006-11-29T20:27:41Z (19 years ago)
From
Bethany Cobb at Yale U <cobb@astro.yale.edu>
B. E. Cobb (Yale), part of the larger SMARTS consortium, reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 061121
(GCN 5823, Page et al.) at several epochs. At a mid-exposure
time of 2006-11-22 07:34 UT (16.2 hours post-burst), the afterglow
is detected in a 36 minute I-band image with a magnitude of I=20.1+/-0.1.
No afterglow is detected in a 30 minute J-band image (with the same
mid-exposure time) to a limiting magnitude of J>19.0+/-0.1.
In two subsequent epochs (mid-exposure times: 64.7 and 87.8 hours
post-burst), 15 minute I and V exposures and 12 minute J and K exposures
were obtained. At the position of the optical afterglow, a possibly
extended source is detected in both V-band images. The source does not
appear to vary significantly between epochs and, therefore, may be the
host galaxy of GRB 061121 (also noted by Malesani et al., GCN 5877),
with a magnitude of V=22.4+/-0.2. This source is detected, with low
significance, in each I-band image. In a combined image of the 2
I-band epochs, the source has a magnitude of I=21.9+/-0.2. The source is
also detected just slightly above the background in a combined J-band
image, which has a 3 sigma limiting magnitude of J>19.3+/-0.1.
The source is not detected in the K-band, to a limiting magnitude
of K>17.8+/-0.1. All magnitudes are calibrated using 2MASS stars in IR
and Landolt standard stars in the optical.