Research On The Symmetry Energy Of Supernova Explosion

A brief review of general theory of the iron core collapse supernova by one dimensional spherically symmetric model is presented in this paper, including the evolution of stars and progenitor stars of supernova, the iron core collapses, shock formation and propagation as well as the neutrino effect. Meanwhile, the numerical simulation named SNⅡ-WLYW89 that developed by Chinese researchers Wang et al has been discussed. A detailed overview of the related problems of numerical simulation especially several changes in process of material experience in the equation of state:four particle uniform statistical equilibrium state, state of uniform nuclear matter, the three particle equilibrium state. In addition, the related theory of the symmetry energy has been introduced, the effect of symmetry energy on the equation of state and the supernova explosion process are also discussed.The equation of state plays an important role on the iron core supernova explosion, which dominates the processes such as gravitational collapse, shock formation and propa-gation. Based on the research of the symmetry energy in the equation of state, we found it can influence the free energy of the material, and then affect the supernova explosion. We take the density dependence of nuclear symmetry energy researched in nuclear physics by Li Baoan et al, which is characterized as 31.6(ρ/ρ0)γ. And we had improved the sym-metry energy term in SNⅡ-WLYW89. Specifically, we use the density dependence of nu-clear symmetry energy in the uniform nuclear matter phase, and in the four particle uni-form statistical equilibrium state we still uses the symmetry energy coefficient of nuclear matter at saturation density which takes 29.3 MeV. Supernova explosions are simulated for progenitor stars model WH08 developed by Woosley and Heger of mass 12M0,13Mo, 14M☉,15M☉,16M☉,17M☉,18M☉,19M☉,21M☉,26M☉,27M☉,28M☉,29M☉,30M☉,31M☉,50M☉,55M☉ The relevant results are used to compare with the old numerical simulation by Wang yiren. In summary, we found that the highest density calculated by using the density dependence of nuclear symmetry energy at the end of the iron core collapse phase can reach 4 times of the nuclear density, as with the Wang Yiren’s results. For the sonic point position, the cal-culation results by using 31.6(ρ/ρ0)γ is larger than Wang Yiren’s. Note that the larger the sonic point position is, the shorter distance it will take for shock wave to reach the boundary of the iron core. For the point that the highest value of the shock wave energy can reach, after using the form of 31.6(ρ/ρ0)γ, the energy value is 1.0foe, and Wang’s is only 0.5foe. Another important result is that the energy took away by neutrino and photodisintegration in the outer core calculated by the density dependence of nuclear symmetry energy is much smaller than Wang Yiren’s original calculation results, which is good for shock wave prop-agating out. All of the above discussions about the progress of four aspects, is conducive to the shock wave spread outward and ultimately achieve supernova explosion success.