The Evolution toward Electron Capture Supernovae: The Flame Propagation and the Pre-bounce Electron-Neutrino Radiation

• Published in: The Astrophysical journal Vol. 871; no. 2; pp. 153 - 172
• Main Authors: Takahashi, Koh, Sumiyoshi, Kohsuke, Yamada, Shoichi, Umeda, Hideyuki, Yoshida, Takashi
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.02.2019; IOP Publishing
• Subjects: abundances > stars: evolution > supernovae: general; Astrophysics; Beta decay; Collapse; Combustion; Computer simulation; Conduction heating; Conductive heat transfer; Dynamic stability; Electron capture; Electrons; Equations of state; Flame propagation; Flames; Gravitational collapse; Ignition; Iron; Isotopes; Neutrinos; neutrinos > nuclear reactions; Neutron stars; Nuclear capture; nucleosynthesis; Phase transitions; Propagation; Radiation; Star & galaxy formation; Star formation; Stellar evolution; Supernovae
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aaf8a8

A critical-mass ONe core with a high ignition density is considered to end in gravitational collapse leading to neutron star formation. Being distinct from an Fe core collapse, the final evolution involves combustion flame propagation, in which complex phase transition from ONe elements into the nuclear statistical equilibrium (NSE) state takes place. We simulate the core evolution from the O+Ne ignition until the bounce shock penetrates the whole core, using a state-of-the-art 1D Lagrangian neutrino radiation hydrodynamic code, in which important nuclear burning, electron capture, and neutrino reactions are taken into account. Special care is also taken in making a stable initial condition by importing the stellar equation of state, which is used for the progenitor evolution calculation, and by improving the remapping process. We find that the central ignition leads to intense e radiation with erg s−1 powered by fast electron captures onto NSE isotopes. This pre-bounce e radiation heats the surroundings by the neutrino-electron scattering, which acts as a new driving mechanism of the flame propagation together with the adiabatic contraction. The resulting flame velocity of ∼108 cm s−1 will be more than one order of magnitude faster than that of a laminar flame driven by heat conduction. We also find that the duration of the pre-bounce e radiation phase depends on the degree of the core hydrostatic/dynamical stability. Therefore, the future detection of the pre-bounce neutrino is important not only to discriminate the ONe core collapse from the Fe core collapse but also to constrain the progenitor hydrodynamical stability.