GCN Circular 10113
Subject
GRB 090926a, SMARTS optical/IR afterglow observations
Date
2009-10-30T07:27:25Z (15 years ago)
From
Bethany Cobb at UC Berkeley <bcobb@astro.berkeley.edu>
B. E. Cobb (UC Berkeley) reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 090926a
(GCN 9933, Bissaldi et al.) over several epochs. For each epoch,
total summed exposure times amounted to 36 minutes in I and
30 minutes in J.
The afterglow of GRB 090926a (e.g. GCN 9937, Haislip et al.;
GCN 9938, Gronwall et al.) is detected in our images with
the following magnitudes (calibrated using Landolt standard stars
in the optical and 2MASS stars in the IR):
time
post-burst I mag J mag
20.60 hrs 18.17+/-0.06 17.28+/-0.07
71.74 hrs 19.53+/-0.07 18.35+/-0.09
119.18 hrs 20.33+/-0.10 19.16+/-0.13
Between ~21 and 119 hours post-burst, the afterglow fades
with a rate of alpha ~ -1.1+/-0.1 (where afterglow flux is
proportional to t^alpha).