G. Tagliaferri, D. Malesani, G. Chincarini, S. Covino, D. Fugazza, M.
Della Valle, L.A. Antonelli, S. Campana, A. Cucchiara, P. D'Avanzo, F.
Fiore, G.L. Israel, D. Lazzati, A. Simoncelli, L. Stella, K. Stamatis,
F.M. Zerbi, on behalf of a larger collaboration, report:
Continuous monitoring of the host galaxy of the INTEGRAL GRB 031203
(Gotz et al., GCN 2459; Prochaska et al., GCN 2475) has been performed
with the ESO telescopes at Paranal and La Silla. We acquired several
exposures in the optical and NIR bands during the period December 03 -
March 01 (up to three months after the high-energy event).
We confirm the variability reported by Bersier et al. (GCN 2544). The
variability pattern is fully consistent with the evolution of a
98bw-like SN at z=0.105 (as measured in our spectra and in agreement
with Prochaska et al., GCN 2482), peaking approximately 20 days after
the burst in the R band. The contribution of such emission is roughly
30% of that of the host galaxy, as determined from the late-time photometry.
Spectra with the VLT were taken on Dec 20, Dec 30 and Mar 01 (17, 27,
and 90 days after the GRB respectively) in an attempt to fully
characterise the observed variability. Subtraction of the late-time
spectrum (taken 90 days after the GRB) from the spectra taken close to
the maximum of the rebrightening reveals the emergence of a spectrum
closely resembling that of SN 1998bw. We therefore conclude that the
observed rebrightening is due to a supernova (Malesani et al. in
We thank the staff at the ESO telescopes (both Paranal and La Silla) for
the extensive work in this campaign, and in particular Malvina Billeres,
Olivier Hainaut, Swetlana Hubrig, Chris Lidman, Gianni Marconi, and
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