A Consistent Modeling of Neutrino-driven Wind with Accretion Flow onto a Protoneutron Star and Its Implications for 56 Ni Production

Details of the explosion mechanism of core-collapse supernovae (CCSNe) are not yet fully understood. There is now an increasing number of successful examples of reproducing explosions in the first-principles simulations, which have shown a slow increase of explosion energy. However, it was recently pointed out that the growth rates of the explosion energy of these simulations are insufficient to produce enough 56 Ni mass to account for observations. We refer to this issue as the “nickel mass problem” (Ni problem, hereafter) in this paper. The neutrino-driven wind is suggested as one of the most promising candidates for the solution to the Ni problem in previous literature, but a multidimensional simulation for this is computationally too expensive to allow long-term investigations. In this paper, we first built a consistent model of the neutrino-driven wind with an accretion flow onto a protoneutron star, by connecting a steady-state solution of the neutrino-driven wind and a phenomenological mass accretion model. Comparing the results of our model with the results of first-principles simulations, we find that the total ejectable amount of the neutrino-driven wind is roughly determined within ∼1 s from the onset of the explosion and the supplementable amount at a late phase ( t e ≳ 1 s) remains M ej ≲ 0.01 M ⊙ at most. Our conclusion is that it is difficult to solve the Ni problem by continuous injection of 56 Ni by the neutrino-driven wind. We suggest that the total amount of synthesized 56 Ni can be estimated robustly if simulations are followed up to ∼2 s.