title: A very luminous magnetar-powered supernova associated with an ultra-long γ-ray burst.
abstract: A new class of ultra-long-duration (more than 10,000 seconds) γ-ray bursts has recently been suggested. They may originate in the explosion of stars with much larger radii than those producing normal long-duration γ-ray bursts or in the tidal disruption of a star. No clear supernova has yet been associated with an ultra-long-duration γ-ray burst. Here we report that a supernova (SN 2011kl) was associated with the ultra-long-duration γ-ray burst GRB 111209A, at a redshift z of 0.677. This supernova is more than three times more luminous than type Ic supernovae associated with long-duration γ-ray bursts, and its spectrum is distinctly different. The slope of the continuum resembles those of super-luminous supernovae, but extends further down into the rest-frame ultraviolet implying a low metal content. The light curve evolves much more rapidly than those of super-luminous supernovae. This combination of high luminosity and low metal-line opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae.
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Excellence Cluster Universe, Technische Universität München, Boltzmannstrasse 2, 85748 Garching, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Greiner
authors.affiliation: 1] Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Browlow Hill, Liverpool L3 5RF, UK [2] Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85748 Garching, Germany.
authors.forename: Paolo A
authors.initials: PA
authors.lastname: Mazzali
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Excellence Cluster Universe, Technische Universität München, Boltzmannstrasse 2, 85748 Garching, Germany [3] Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany.
authors.forename: D Alexander
authors.initials: DA
authors.lastname: Kann
authors.affiliation: European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile.
authors.forename: Thomas
authors.initials: T
authors.lastname: Krühler
authors.affiliation: 1] INAF, Institute of Space Astrophysics and Cosmic Physics, via P. Gobetti 101, 40129 Bologna, Italy [2] Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Pian
authors.affiliation: Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Browlow Hill, Liverpool L3 5RF, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: Prentice
authors.affiliation: Departamento de Ciencias Fisicas, Universidad Andres Bello, Avenida Republica 252, Santiago, Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Olivares E
authors.affiliation: 1] Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany [2] INAF, Institute of Space Astrophysics and Cosmic Physics, via P. Gobetti 101, 40129 Bologna, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Rossi
authors.affiliation: Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany.
authors.forename: Sylvio
authors.initials: S
authors.lastname: Klose
authors.affiliation: 1] Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85748 Garching, Germany [2] European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Taubenberger
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Knust
authors.affiliation: American River College, Physics and Astronomy Department, 4700 College Oak Drive, Sacramento, California 95841, USA.
authors.forename: Paulo M J
authors.initials: PM
authors.lastname: Afonso
authors.affiliation: Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Browlow Hill, Liverpool L3 5RF, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Ashall
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Technische Universität München, Physik Department, James-Franck-Strasse, 85748 Garching, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Bolmer
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Corentin
authors.initials: C
authors.lastname: Delvaux
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Diehl
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Astrophysics Data System, Harvard-Smithonian Center for Astrophysics, Garden Street 60, Cambridge, Massachusetts 02138, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Elliott
authors.affiliation: Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 128 00 Prague 2, Czech Republic.
authors.forename: Robert
authors.initials: R
authors.lastname: Filgas
authors.affiliation: DARK Cosmology Center, Niels-Bohr-Institut, University of Copenhagen, Juliane Maries Vej 30, 2100 København, Denmark.
authors.forename: Johan P U
authors.initials: JP
authors.lastname: Fynbo
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: John F
authors.initials: JF
authors.lastname: Graham
authors.affiliation: Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany.
authors.forename: Ana Nicuesa
authors.initials: AN
authors.lastname: Guelbenzu
authors.affiliation: Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Browlow Hill, Liverpool L3 5RF, UK.
authors.forename: Shiho
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: 1] DARK Cosmology Center, Niels-Bohr-Institut, University of Copenhagen, Juliane Maries Vej 30, 2100 København, Denmark [2] Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Giorgos
authors.initials: G
authors.lastname: Leloudas
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Universita della Calabria, 87036 Arcavacata di Rende, via P. Bucci, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Savaglio
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Patricia
authors.initials: P
authors.lastname: Schady
authors.affiliation: Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schmidl
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Technische Universität München, Physik Department, James-Franck-Strasse, 85748 Garching, Germany.
authors.forename: Tassilo
authors.initials: T
authors.lastname: Schweyer
authors.affiliation: 1] Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany [2] Astrophysics Data System, Harvard-Smithonian Center for Astrophysics, Garden Street 60, Cambridge, Massachusetts 02138, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Sudilovsky
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Mohit
authors.initials: M
authors.lastname: Tanga
authors.affiliation: Roger Williams University, 1 Old Ferry Road, Bristol, Rhode Island 02809, USA.
authors.forename: Adria C
authors.initials: AC
authors.lastname: Updike
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: van Eerten
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany.
authors.forename: Karla
authors.initials: K
authors.lastname: Varela