Nucleosynthesis and neutrino signals of compact star weak explosionsHYBRID

In this talk, I will briefly discuss two hypothetical weak explosion mechanisms of compact star: subminimal neutron star explosions and accretion-induced collapse (AIC) of white dwarfs. Although these events are not verified through electromagnetic observations yet, they may be identified by the new generation of neutrino observatories. Also, the nucleosynthesis products of these events are also indirect evidence of their existence.

If a stable mass transfer could be established for a highly asymmetric close neutron star binary, the system’s asymmetry would be further enhanced until the lighter neutron star reaches the minimum mass allowed by the equation of state. We perform reactive hydrodynamic simulations of a minimum-mass neutron star, and we show that it undergoes delayed explosion after mass removal from its surface, resulting in an electron antineutrino burst with a peak luminosity of ∼10$^{50}$erg s$^{−1}$ and a robust r-process nucleosynthesis in the ejecta. Lanthanides and heavy elements near the 2nd and 3rd r-process peaks are synthesized, suggesting that subminimal neutron star explosions could be an important source of solar chemical elements. 

A typical white dwarf with a carbon-oxygen core may undergo a thermonuclear explosion when reaching the Chandrasekhar limit. However, it may go through the AIC due to electron capture if it has an oxygen-neon-magnesium core. We present neutrino radiation hydrodynamic simulations of AIC. A proto-neutron star is formed after the AIC, and a neutrino burst is emitted, comparable to that of a core-collapse supernova. The ejecta mass of AIC could be up to ∼10$^{-2}$ M☉, and the 1st neutron-capture peak elements (Sr, Y, Zr) could be abundantly synthesized in the low electron fraction component of the ejecta.