title: Cobalt-56 γ-ray emission lines from the type Ia supernova 2014J.
abstract: A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or a pair of merging white dwarfs. The explosion fuses a large amount of radioactive (56)Ni (refs 1-3). After the explosion, the decay chain from (56)Ni to (56)Co to (56)Fe generates γ-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of (56)Co lines at energies of 847 and 1,238 kiloelectronvolts and a γ-ray continuum in the 200-400 kiloelectronvolt band from the type Ia supernova 2014J in the nearby galaxy M82. The line fluxes suggest that about 0.6 ± 0.1 solar masses of radioactive (56)Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10,000 ± 3,000 kilometres per second. The observed γ-ray properties are in broad agreement with the canonical model of an explosion of a white dwarf just massive enough to be unstable to gravitational collapse, but do not exclude merger scenarios that fuse comparable amounts of (56)Ni.
authors.affiliation: 1] Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia [2] Max Planck Institute for Astrophysics, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Churazov
authors.affiliation: 1] Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia [2] Max Planck Institute for Astrophysics, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany.
authors.forename: R
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authors.affiliation: Institute for Space Sciences (ICE-CSIC/IEEC), 08193 Bellaterra, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Isern
authors.affiliation: 1] Université de Toulouse, UPS-OMP, IRAP, Toulouse, France [2] CNRS, IRAP, 9 Avenue colonel Roche, BP 44346, F-31028 Toulouse Cedex 4, France.
authors.forename: J
authors.initials: J
authors.lastname: Knödlseder
authors.affiliation: 1] Université de Toulouse, UPS-OMP, IRAP, Toulouse, France [2] CNRS, IRAP, 9 Avenue colonel Roche, BP 44346, F-31028 Toulouse Cedex 4, France.
authors.forename: P
authors.initials: P
authors.lastname: Jean
authors.affiliation: APC, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 75205 Paris Cedex 13, France.
authors.forename: F
authors.initials: F
authors.lastname: Lebrun
authors.affiliation: Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya Street, 119017 Moscow, Russia.
authors.forename: N
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authors.lastname: Chugai
authors.affiliation: Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia.
authors.forename: S
authors.initials: S
authors.lastname: Grebenev
authors.affiliation: ETSAV, Universitat Politecnica de Catalunya, Carrer Pere Serra 1-15, 08173 Sant Cugat del Valles, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Bravo
authors.affiliation: 1] Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997, Russia [2] Moscow Institute of Physics and Technology, Institutsky pereulok 9, 141700 Dolgoprudny, Russia.
authors.forename: S
authors.initials: S
authors.lastname: Sazonov
authors.affiliation: LUPM, Université Montpellier 2, CNRS/IN2P3, CC 72, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France.
authors.forename: M
authors.initials: M
authors.lastname: Renaud