GCN Circular 1273
Subject
GRB011121, possible supernova association
Date
2002-03-15T17:16:11Z (23 years ago)
From
Peter Garnavich at U of Notre Dame <pgarnavi@miranda.phys.nd.edu>
P. M. Garnavich, S. T. Holland (Notre Dame), S. Jha, R. P. Kirshner,
D. Bersier, and K. Z. Stanek (CfA)
We have reanalyzed R-band images of GRB 011121 obtained with the
Walter Baade 6.5m Magellan telescope on 2001 Dec. 4.32 in light
of the recently released HST images taken near the same time
(Bloom, GCN 1260). The brightness of the afterglow in the Magellan
data deviated from the steep powerlaw decline seen in the
first three days after the burst and we attributed this to contamination
from the host galaxy (e.g. Phillips et al. GCN 1164). However the Magellan
magnitude of R=23.0+\-0.1, obtained by point-spread-function fitting is
consistent with the WFPC2 magnitude of f702w=23.16+\-0.08 which
has minimal host contamination. Both observations are nearly
2 magnitudes brighter than the early-time extrapolation.
The full light curve is well fit by an initial powerlaw with
index of 1.71+\-0.05 plus the light curve of SN 1998bw stretched
and faded to a redshift of z=0.36 (Infante et al. GCN 1152). The
Dec. 4 data is 10 days after explosion in the rest frame, while
SN 1998bw peaked 17 days after GRB 980425, so later epochs
may show a small rise in the f702w magnitude before final
fading. The light curve can be viewed at
http://www.nd.edu/~pgarnavi/grb011121/grb011121_sn.ps
Assuming a flat cosmology with Omega_m=0.3 and a Hubble
parameter of 65 km/s/Mpc, we derive an absolute magnitude for
the possible supernova on Dec. 4 of Mv=-19.3+\-0.2 (corrected
for a large Galactic extinction but not for host extinction), consistent
with SN 1998bw near maximum. These observations could be strong
evidence for a SN-GRB connection.
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