UC San Diego

The existence of super-massive (> 10^4M⊙) Pop III stars has been theorized, but never observed. If such stars were to have existed during early galaxy formation, it has long been thought that in absence of heavy metals (A > 4), they would have collapsed due to instabilities caused by general relativity. Such a collapse would have resulted in the creation of a super- massive black hole, possibly emitting gravitational waves if accompanied by an anisotropic neutrino burst. Super-massive black holes have been detected very early on in galaxy formation (red shift: z ≈ 7), and their origin remains unknown. Gravitational waves created by such a collapse may be detectable by next generation gravitational wave detectors.

Recent simulations have suggested that a narrow range of super-massive stars with masses around 5 × 10^4M⊙ may have exploded due to simultaneously reaching the general relativistic instability and the ignition of triple-α fusion. If such explosions were to have occurred, depending on their frequency of occurrence, they may have left behind a measurable elemental signature of heavy elements in an otherwise primordial elemental composition during early galaxy formation.

This dissertation details the investigation of post-instability energetics, both from a theoretical stand point as well as via simulations using the KEPLER stellar evolution code. Previous research has found that for a small range of stars with masses around 5 × 10^4M⊙, due to the extreme temperature sensitivity of the triple-α process at its ignition point (~2 × 10^8 K), there is a theoretical basis for accelerated nuclear energy production to possibly reverse the collapse before too much energy is lost in electron-positron pair annihilation neutrinos combined with in-falling kinetic energy. However, complimentary findings via simulations were not found to be satisfactory. Future three dimensional simulations with high precision accounting of nuclear energy production as well as energy losses and kinematics would be necessary to definitively conclude whether such explosions are energetically possible.