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

Area of Science:

• Astrophysics
• Cosmic Explosions
• Nuclear Astrophysics

Background:

• Type Ia supernovae result from thermonuclear explosions of white dwarfs.
• These explosions synthesize radioactive nickel-56 (56Ni), which decays to produce gamma-ray photons.
• Gamma-ray emission from supernovae provides insights into their explosion mechanisms and synthesized elements.

Purpose of the Study:

• To detect and analyze gamma-ray emission from the Type Ia supernova 2014J.
• To determine the amount of synthesized radioactive nickel-56 (56Ni) and the ejecta expansion velocity.
• To test theoretical models of white dwarf explosions.

Main Methods:

• Detection of gamma-ray lines from cobalt-56 (56Co) at 847 and 1,238 kiloelectronvolts.
• Measurement of the gamma-ray continuum in the 200-400 kiloelectronvolt band.
• Analysis of line broadening to infer ejecta expansion velocity.

Main Results:

• Detection of characteristic 56Co gamma-ray lines and continuum emission from supernova 2014J.
• Estimated synthesis of approximately 0.6 ± 0.1 solar masses of 56Ni.
• Determined a mass-weighted ejecta expansion velocity of 10,000 ± 3,000 kilometers per second.

Conclusions:

• The observed gamma-ray properties of supernova 2014J align with models of white dwarf explosions.
• The results support scenarios involving a single white dwarf near the Chandrasekhar mass limit.
• Merger scenarios producing similar amounts of 56Ni are not excluded by the data.