A Numerical Example of the Collapse of a Rotating Magnetized Star

Abstract

The time history of a star of 7 M0. undergoing gravitational collapse due to iron decomposition is calculated numerically. The angular velocity assumes a vortezlike distribution which halts the collapse at a relatively low density, 1011 g . The large shear in the velocity field gives an enhancement of about 100 in the multiplication of magnetic-field energy over the energy multiplication from simple compression. The combined effect of rotation and magnetic field is to produce an axial jet. At a radius of 4 X 10 cm where the jet material leaves the calculational grid, the jet carries a mass of 2.1 X 1031 g and a total energy of 1.6 X 1050 ergs. The energy is principally kinetic, 1.6 X 10 ergs, but it also has a large magnetic energy equal to 3.5 X 10 ergs, and only 1.1 X 10 ergs of internal energy.