[vsnet-grb-info 10227] GRB 110206A: SMARTS optical/IR afterglow decay

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11675
SUBJECT: GRB 110206A: SMARTS optical/IR afterglow decay
DATE:    11/02/08 22:24:32 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 110206A (GCN 11654,
Mereghetti et al.) with a mid-exposure time of 34.2 hours post-burst
(2011-02-08 04:22 UT).  Total summed exposure times amounted to
36 minutes in I and 30 minutes in J.

In agreement with Elliott et al. (GCN 11669), we observe that the
candidate optical afterglow of GRB 110206A (GCN 11662, Hoversten et al.
and GCN 11665, Elliott et al.) has decayed significantly from our
previous observations (GCN 11668), indicating that this is the optical
afterglow of GRB 110206A.  Preliminary comparison to Landolt standard
stars indicates the following magnitude for the optical afterglow:

time post-burst       I mag
 6.8 hours              20.6+/-0.1
34.2 hours             21.6+/-0.2

This indicates that the decay rate of the burst between ~7 and 34 hours
post burst is alpha ~ 0.6 (where afterglow flux is proportional
to t^-alpha).