Core collapse

Frequently produced by some type of overloading, such as an overload resulting in a collapse of the fiber core in swabbing lines. This may also occur in cable-tool lines as a result of concentrated pulsating or surging forces that may contribute to fiber-core collapse. 

Fig. 5.10. Upper panel chemical profile of a 25 Af0 star immediately before core collapse. (Note change in horizontal scale at 2 Af0.) Lower panel the same, after modification by explosive nucleosynthesis in a supernova outburst. The amount of 56Ni (which later decays to 56Fe) ejected depends on the mass cut, somewhere in the 28Si 56Ni zone, and is uncertain by a factor of 2 or so. Adapted from Woosley and Weaver (1982).

Species are given with their proto-solar abundance by mass fraction, after Lodders (2003). The last column gives the yield calculated by Nomoto et al. for core-collapse supemovae within a Salpeter IMF between mass limits of 0.07 and 50 Mq. 

Burrows, A., Ott, C.D., Meakin, C. (2003), Topics in core-collapse supernova theory , astro-ph/0309684. 

The following stage is core collapse caused by electron capture or photodisintegration of iron. According to the traditional view, collapse leads to formation of a neutron star which cools by neutrino emission and decompression of matter when it reaches nuclear density (10 g cm ). The rebound that follows generates a shock wave which is capable of reigniting a good few nuclear reactions as it moves back out across the stellar envelope. 

Neutrinos are usually evoked as detonators, triggering or driving the explosion of massive stars. The gravitational energy freed by core collapse of a massive star, some 10 erg, is mainly evacuated by neutrinos. These pour out in such inordinate amounts that if just 1% of their energy is communicated to matter in the envelope, the whole thing will be blasted out of existence. 

Once the helium has been used up, the same process is repeated. The star cools, the core collapses further and heats up, and new fusion processes are ignited carbon and oxygen are fused to make sodium, magnesium, silicon, and sulphur. Gradually, the Periodic Table emerges in this juddering, unstable furnace. 

These elements are scattered throughout the universe when massive stars end their lives. When there is no fuel left to burn, the core collapses once again, and there is nothing to stop it. A shock wave from this collapse causes a rebound that fuels an enormous explosion a supernova. The outer layers of the star are blown out into space, and the energy that is released triggers new nucleosynthesis reactions, which make the heavy elements beyond bismuth - up to uranium, and at least a little beyond. 

These parameters define an entirely unremarkable blue supergiant. Conventional wisdom had it that Supemovae of Type n occur either in red supeigiants, or perhaps, in the Wolf-Rayet phase of evolution. The central problem for the evolutionary models is therefore, how can the moment of core collapse be contrived to occur in a blue supergiant star There have already been many attempts made to address this question, and from these it is apparent that the main sequence mass must have been in the range 15-20 M . These models teach us that the end-point of evolution is... 

II. TYPE lb MASSIVE-STAR CORE-COLLAPSE OR WHITE-DWARF DETONATION ... 

After approximately one minute the shock initiated by iron core collapse arrives at the outer edge of the helium core whose radius is typically 5 X 1010 cm. The hydrodynamic interaction with the envelope slows the helium core down, the deceleration propagating into the core as a reverse shock. Meanwhile the outgoing shock continues though the hydrogen. The time when the shock breaks through the surface of the envelope can be estimated (Shigeyama et a1. 1987 Woosley 1987),... 

Models for SN1987a have recently been extensively discussed by Woosley [1 ]. We have used model 10H from that paper for the spectrum calculation. As discussed there in detail, this model is the core of a 20 Mg, star which has lost 4 M 0f mass in a wind. The core collapse and subsequent explosioh produces ejecta with 1.4xl051 ergs and 0.08 M of ssNi. As discussed in an earlier section of this paper, this model is not thin in the continuum until roughly 300 days after explosion. In fact, the situation is worse than this, since... 

Later Quasi-Steady Expansion After the core collapse a weak shock... 

Observing the Nucleosynthesis from Core Collapse Supernovae... 

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