GCN Circular 8639
Subject
GRB 081128: afterglow observations
Date
2008-12-08T08:35:39Z (15 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@astro.ku.dk>
D. Malesani, J.P.U. Fynbo, G. Leloudas (DARK/NBI), H. Pedersen (NBI), P.
Jakobsson (Univ. Iceland), S.-M. Niemi, H. Uthas, and C. Villforth
(NOT), report on behalf of a larger collaboration:
We observed the field of GRB 081128 (Margutti et al., GCN 8571) with the
Nordic Optical Telescope equipped with ALFOSC. Observations were carried
out on two epochs, first on 2008 Nov 28.962 (0.24 days after the GRB) in
the V, R and i bands and then on Dec 7.827 (9.10 days after the GRB) in
the R band. In the first epoch we detect the afterglow candidate
reported by Wang et al. (GCN 8572) in all filters. We estimate R=22.3 +-
0.1 assuming R=17.91 for the USNO star at RA = 01:23:11.73, Dec =
+38:07:43.58 (consistent with the calibration of Guidorzi et al., GCN
8577; C. Guidorzi, priv. comm.). In the second epoch, the afterglow
candidate remains undetected to a limit R > 23.5, and we hence confirm
that this source is the GRB afterglow. We note that the V-band detection
sets a limit on the GRB redshift, z <~ 5.
We also detect in both epochs a second object at the border of the XRT
error circle (RA = 01:23:12.98, Dec = +38:07:38.4), which is likely the
one reported by Guidorzi et al. (GCN 8577), with a magnitude R = 22.7.
The angular separation from the afterglow is 1.2".