"We report the first ever detection of 56Co lines at 847 and 1237 keV and a continuum in the 200-400 keV band from the Type Ia supernova SN2014J in M82 with INTEGRAL observatory. The data were taken between 50th and 100th day since the SN2014J outburst. The line fluxes suggest that 0.62±0.13 M⊙ of radioactive 56Ni were synthesized during the explosion. Line broadening gives a characteristic ejecta expansion velocity Ve∼2100±500 km s−1. The flux at lower energies (200-400 keV) flux is consistent with the three-photon positronium annihilation, Compton downscattering and absorption in the ∼ 1.4 M⊙ ejecta composed from equal fractions of iron-group and intermediate-mass elements and a kinetic energy Ek∼1.4 1051 erg. All these parameters are in broad agreement with a "canonical" model of an explosion of a Chandrasekhar-mass White Dwarf (WD), providing an unambiguous proof of the nature of Type Ia supernovae as a thermonuclear explosion of a solar mass compact object."
The results described in the previous section can be summarized as follows: (i) INTEGRAL detects significant emission from two brightest gamma-ray lines associated with 56 Co decay, (ii) the lines are significantly broadened, (iii) low energy (<400 keV) emission is present. We now discuss the most basic implications of these results.
The detection of key gamma-ray lines of radioactive cobalt 56 Co provides solid proof of the interpretation of Type Ia supernova as a thermonuclear explosion of near-Chandrasekhar-mass WD. There is broad agreement between the observed fluxes and line broadening with the canonical model of the SNIa at the stage when the decay of 56 Co dominates. More thorough comparison of the INTEGRAL data with the detailed models of emerging gamma-ray flux and optical data to differentiate between different explosion scenarios will be presented in subsequent publications.
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