Magnetorotational Collapse of Population III Stars

We performed a series of two-dimensional magnetorotational core-collapse simulations of Population III stars. Changing the initial distributions of the rotation and magnetic fields prior to collapse in a parametric manner, we computed 19 models. By so doing, we systematically investigated how rotation and magnetic fields affect the collapse dynamics, and explored how the properties of black-hole formations and neutrino emissions could be affected. As for microphysics, we employed a realistic equation of state, and approximated neutrino transfer by a multiflavour leakage scheme. With these computations, we found that jet-like explosions are obtained by magneto-driven shock waves if the initial magnetic field is as large as 10¹²G. We point out that although the black-hole masses at formation decrease with the initial field strength, they increase with the initial rotation rates. As for the neutrino properties, we point out that the degree of differential rotation plays an important role in determining which species of the neutrino luminosity is more dominant than the others. Furthermore, we find that stronger magnetic fields make the peak neutrino luminosities smaller, because the magnetic pressure acts to halt collapse in the central regions, leading to a suppression of the releasable gravitational binding energies.