[vsnet-grb-info 3345] GRB 060526: SMARTS optical/IR afterglow observations

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5180
SUBJECT: GRB 060526: SMARTS optical/IR afterglow observations
DATE:    06/05/28 19:11:24 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 060526
(GCN 5162, Campana et al.) with a mid-exposure time of
2006-05-27 01:13 UT (~8.7 hours post-burst) and
again at 2006-05-27 04:07 UT (~11.6 hours post-burst).
Total summed exposure times for each observation amounted
to 36 minutes in I and 30 minutes in J.

The afterglow of GRB 060526 is visible in each combine image.
The preliminary magnitudes reported below were calibrated using
several USNO-B1.0 stars in the I-band and two 2MASS standards in J.
[The errors on the photometric calibration are ~0.2 in I and ~0.02
in J; these errors are in addition to the statistical errors listed
below.]

time
post-burst      I magnitude             J magnitude
------------------------------------------------------
 8.7 hours      18.99 +/- 0.02          18.16 +/- 0.06
11.6 hours      19.31 +/- 0.02          18.58 +/- 0.07


The afterglow decay index is constrained by our observations to be
alpha = 1.2 +/- 0.2 from 8.7 to 11.6 hours post-burst.  This
value is in agreement with the decay value from 5 to 16 hours
post-burst reported by Khamitov et al. (GCN 5173)
and Halpern et al. (GCN 5176).