The High Ratio of 44Ti/56Ni in Cassiopeia A and the Axisymmetric Collapse-driven Supernova Explosion
Abstract
The large abundance ratio of 44Ti/56Ni in Cassiopeia A is puzzling. In fact, the ratio seems to be larger than the theoretical constraint derived by Woosley & Hoffman. However, this constraint is obtained on the assumption that the explosion is spherically symmetric, whereas Cas A is famous for the asymmetric form of the remnant. Recently, Nagataki et al. calculated the explosive nucleosynthesis of axisymmetrically deformed collapse-driven supernova. They reported that the ratio of 44Ti/56Ni was enhanced by the stronger alpha-rich freezeout in the polar region. In this Letter, we apply these results to Cas A and examine whether this effect can explain the large amount of 41Ti and the large ratio of 44Ti/56Ni. We demonstrate that the conventional, spherically symmetric explosion model cannot explain the 44Ti mass produced in Cas A if its lifetime is shorter than ~80 yr and the intervening space is transparent to the gamma-ray line from the decay of 44Ti. On the other hand, we show that the axisymmetric explosion models can solve the problem. We expect the same effect from a three-dimensionally asymmetric explosion, since the stronger alpha-rich freezeout will also occur in that case in the region where the larger energy is deposited.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1998
- DOI:
- 10.1086/311089
- arXiv:
- arXiv:astro-ph/9807015
- Bibcode:
- 1998ApJ...492L..45N
- Keywords:
-
- STARS: SUPERNOVAE: GENERAL;
- STARS: SUPERNOVAE: INDIVIDUAL ALPHANUMERIC: SN 1987A;
- STARS: SUPERNOVAE: INDIVIDUAL NAME: CASSIOPEIA A;
- NUCLEAR REACTIONS;
- NUCLEOSYNTHESIS;
- ABUNDANCES;
- Nuclear Reactions;
- Nucleosynthesis;
- Abundances;
- Stars: Supernovae: General;
- Stars: Supernovae: Individual: Name: Cassiopeia A;
- Stars: Supernovae: Individual: Alphanumeric: SN 1987A;
- Astrophysics
- E-Print:
- 10 pages, LaTeX text and 3 postscript figures