title: Early ⁵⁶Ni decay gamma rays from SN2014J suggest an unusual explosion.
abstract: Type Ia supernovae result from binary systems that include a carbon-oxygen white dwarf, and these thermonuclear explosions typically produce 0.5 solar mass of radioactive (56)Ni. The (56)Ni is commonly believed to be buried deeply in the expanding supernova cloud. In SN2014J, we detected the lines at 158 and 812 kiloelectron volts from (56)Ni decay (time ~8.8 days) earlier than the expected several-week time scale, only ~20 days after the explosion and with flux levels corresponding to roughly 10% of the total expected amount of (56)Ni. Some mechanism must break the spherical symmetry of the supernova and at the same time create a major amount of (56)Ni at the outskirts. A plausible explanation is that a belt of helium from the companion star is accreted by the white dwarf, where this material explodes and then triggers the supernova event.
authors: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85741 Garching, Germany rod@mpe.mpg.de.
authors: Roland
authors: R
authors: Diehl
authors: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85741 Garching, Germany.
authors: Thomas
authors: T
authors: Siegert
authors: Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany.
authors: Wolfgang
authors: W
authors: Hillebrandt
authors: Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia.
authors: Sergei A
authors: SA
authors: Grebenev
authors: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85741 Garching, Germany.
authors: Jochen
authors: J
authors: Greiner
authors: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85741 Garching, Germany.
authors: Martin
authors: M
authors: Krause
authors: The Oskar Klein Centre and Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden.
authors: Markus
authors: M
authors: Kromer
authors: Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, and Kavli Institute (WPI), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan.
authors: Keiichi
authors: K
authors: Maeda
authors: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Emil-Fischer-Strasse 31, 97074 Würzburg, Germany.
authors: Friedrich
authors: F
authors: Röpke
authors: Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany.
authors: Stefan
authors: S
authors: Taubenberger