GCN Circular 5734

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 061019
(GCN 5728
Not found
 
 
, Guidorzi et al.) with a mid-exposure time of
2006-10-19 07:29 UT, which is ~3.2 hours post-burst.
Total summed exposure times amounted to 15 minutes in I and V and
12 minutes in J and K.

Within the error region of the X-ray afterglow detection
(GCN 5729
Not found
 
 
, Guidorzi et al.), we detect the source reported
by Covino et al. (GCN 5730
Not found
 
 
), in the I, J and K bands.
The source is not detected in V, to a limiting magnitude
of ~22.  The preliminary magnitudes of this source
(calibrated against several 2MASS stars in IR and USNO-B1.0
stars in the optical) are:

time post-
burst (hrs)     I               J               K
------------------------------------------------------------
3.2             20.2 +/- 0.3    17.6 +/- 0.1    15.4 +/- 0.1

(not corrected for the expected high Galactic extinction)

This indicates that the source has faded by ~1 magnitude
since the Covino et al. K-band observations, taken
~1.1 hours post-burst.  This source is therefore confirmed to
be the afterglow of GRB 061019, wth a decay rate of alpha ~ -0.8.

[GCN OPS NOTE(19oct06): Per author's request, the J-band value
was corrected from 17.9 to 17.6.]