Cobalt-56 gamma-ray emission lines from the type Ia supernova 2014J

TL;DR

This paper reports the detection of gamma-ray emission lines from supernova 2014J, providing insights into the radioactive nickel produced and the explosion dynamics, supporting the white dwarf explosion model.

Contribution

First detection of 56Co gamma-ray lines from supernova 2014J, offering direct evidence of radioactive nickel synthesis and ejecta velocity in a type Ia supernova.

Findings

Detected 56Co gamma-ray lines at 847 and 1238 keV

Estimated 0.6 solar masses of 56Ni synthesized

Ejecta expansion velocity approximately 10,000 km/s

Abstract

A type Ia supernova is thought to be a thermonuclear explosion of either a single carbon-oxygen white dwarf or of a pair of merging white dwarfs. The explosion fuses a large amount of radioactive 56Ni. After the explosion, the decay chain from 56Ni to 56Co to 56Fe generates gamma-ray photons, which are reprocessed in the expanding ejecta and give rise to powerful optical emission. Here we report the detection of 56Co lines at energies of 847 and 1238 keV and a gamma-ray continuum in the 200-400 keV 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 56Ni were synthesized during the explosion. The line broadening gives a characteristic mass-weighted ejecta expansion velocity of 10000 +/- 3000 km/s. The observed gamma-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 immediately exclude more complicated merger scenarios, which fuse comparable amount of 56Ni.