Multiwavelength analysis of three supernovae associated with gamma-ray bursts observed by GROND^⋆

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße 1, 85740 Garching, Germany
e-mail: f.olivares.e@gmail.com
² Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, Chile
³ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
⁴ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
⁵ Physics Department, University of Calabria, Arcavacata, 87036 Rende, Italy
⁶ Università degli studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
⁷ American River College, Physics and Astronomy Dpt., 4700 College Oak Drive, Sacramento, CA 95841, USA
⁸ Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22,  12800   Prague 2,  Czech Republic

Received: 21 May 2013
Accepted: 30 January 2015

Abstract

Context. After the discovery of the first connection between γ-ray bursts (GRBs) and supernovae (SNe) almost two decades ago, tens of SN-like rebrightenings have been discovered and about seven solid associations have been spectroscopically confirmed to date.

Aims. We determine the luminosity, evolution, and origin of three SN rebrightenings in GRB afterglow light curves at z ~ 0.5 along with accurate determinations of the host-galaxy extinction. We estimate physical parameters of the SN explosions, such as synthesised ⁵⁶Ni mass, ejecta mass, and kinetic energy.

Methods. We employ GROND optical/NIR data and Swift X-ray/UV data to estimate the host-galaxy extinction by modelling the afterglow spectral energy distribution, to determine the SN luminosity and evolution, and to construct quasi-bolometric light curves. The latter are corrected for the contribution of the NIR-bands using data available in the literature and black-body fits. We employ Arnett’s analytic approach to obtain the physical parameters of the explosion.

Results. The SNe 2008hw, 2009nz, and 2010ma observed by GROND exhibit 0.80, 1.15, and 1.78 times the optical (r′-band) luminosity of SN 1998bw, respectively. While SN 2009nz exhibits an evolution similar to SN 1998bw, SNe 2008hw and 2010ma show earlier peak times. The quasi-bolometric light curves (340–2200 nm) confirm the large luminosity of SN 2010ma (1.4 × 10⁴³ erg s^-1), while SNe 2008hw and 2009nz reached a peak luminosity closer to that of SN 1998bw. The modelling indicates in ⁵⁶Ni masses of around 0.4−0.5 M_⊙.

Conclusions. By means of a very comprehensive data set, we found that the luminosity and the ⁵⁶Ni mass of SNe 2008hw, 2009nz, and 2010ma resembles those of other known GRB-associated SNe. These findings strengthens previous claims of GRB-SNe being brighter than stripped-envelope SNe unaccompanied by GRBs.