[vsnet-grb-info 4067] GRB 061121, SMARTS optical/IR observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5878
SUBJECT: GRB 061121, SMARTS optical/IR observations
DATE:    06/11/29 20:27:41 GMT
FROM:    Bethany Cobb at Yale U  <cobb at 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.