GCN Circular 8662
Subject
GRB 081007: Detection of a Supernova
Date
2008-12-12T16:46:46Z (15 years ago)
From
Edo Berger at Harvard <eberger@cfa.harvard.edu>
Alicia Soderberg, Edo Berger (Harvard CfA), and Derek Fox (PSU) report on
behalf of a larger collaboration:
"We imaged the optical counterpart of GRB 081007 (Baumgartner et al., GCN
8330) with Gemini-S/GMOS in the griz filters on three separate epochs: Oct
24.02, Nov 2.01, and Dec 5.04 UT corresponding to 16.80, 25.79, and 58.82
days after the burst, respectively.
Using the ISIS image subtraction package and adopting our third epoch as a
template image, we find a residual source in the first and second epochs
at a position coincident with that of the early afterglow. A comparison
of the residual flux indicates that the transient increased by roughly 0.4
mag in i-band between the first and second epochs and then subsequently
faded. We attribute this photometric evolution to a supernova component,
in line with the recent report of spectroscopic evidence for an underlying
Type Ibc supernova (Della Valle et al., CBET 1602).
Accounting for a redshift of z=0.53 (Berger et al., GCN 8335), the
k-corrected absolute magnitude of the object in our second epoch i-band
image is fainter than that SN 1998bw at the same (rest-frame) time.
Further analysis is on-going."