High ratio of Ti-44/Ni-56 in Cas A and axisymmetric collapse-driven supernova explosion

Abstract

Calculation of the explosive nucleosynthesis of an axisymmetrically deformed collapse-driven supernova was reported recently. It was reported that the ratio of Ti-44/Ni-56 was enhanced by the stronger alpha-rich freezeout in the polar region. It is examined whether this effect can explain the large amount of Ti-44 and the large ratio of Ti-44/Ni-56 applying these results to Cassiopeia A (Cas A). It is demonstrated that the conventional spherically symmetric explosion model cannot explain the Ti-44 mass-produced in Cas A if its lifetime is shorter than approximately 80 years. On the other hand, it is shown that the axisymmetric explosion models can solve the problem. The same effect will be expected from a three-dimensionally asymmetric explosion.

軸対称に変形した崩壊駆動型超新星の爆発的核種合成についての計算が最近報告された。それによると、極地域でα富化凍結がより強いのでTi-44/Ni-56の比は増大する。この結果をカシオペヤA(Cas A)に適用して、Ti-44の量が多いこととTi-44/Ni-56の比が大きいことをこの効果で説明できるか否かを検討した。Ti-44の寿命が約80年よりも短い場合には、Cas A中で生成されるTi-44の質量を従来の球対称の爆発模型では説明できないことを示した。一方、軸対称爆発模型はこの問題を解決出来ることを示した。3次元的に非対称な爆発からも同様の効果が期待できる。