[vsnet-grb-info 12564] GRB 121024A: SMARTS optical/IR afterglow observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13928
SUBJECT: GRB 121024A: SMARTS optical/IR afterglow observations
DATE:    12/10/29 21:00:20 GMT
FROM:    Bethany Cobb at GWU  <bcobb at gwu.edu>

B. E. Cobb (GWU), reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained
optical/IR imaging of the error region of GRB 121024A (GCN 13886,
Pagani et al.)  over several epochs (with mid-exposure times of
2012-10-24 03:51 UT, 06:10 UT, 08:12 UT and 2012-10-25 06:53 UT).
For each epoch, several dithered images were obtained with
total summed exposure times of 15 min in V and I and 12 min in
J and K.  For the final epoch, total exposure times were
36 min in I and 30 min in J.

The fading afterglow of GRB 121024A (e.g. GCN 13887, Klotz et al.; GCN
13888, Jelinek et al.; GCN 13891, Knust et al.) was detected with the
following magnitudes (or 3-sigma limits):

mid-exposure
time
(hours)         I mag            J mag            K mag
0.90722       18.0 +/- 0.1   16.7 +/- 0.1   15.2 +/- 0.2
3.23611       19.4 +/- 0.1   17.9 +/- 0.1   16.3 +/- 0.2
5.27333       19.8 +/- 0.1   > 18.0           > 16.4
27.95278      > 21.9          > 19.3           ...

(Optical photometry is calibrated against USNO-B1.0 stars
and IR photometry is calibrated against 2MASS stars in the field.)