Three-dimensional magnetohydrodynamical simulations of gravitational collapse of a 15 m⊙ star

Abstract

We introduce our two different newly developed, three-dimensional magnetohydrodynamical codes in detail. One of them is written in the Newtonian limit (NMHD) and the other is a fully general relativistic code (GRMHD). Both codes employ adaptive mesh refinement and, in GRMHD, the metric is evolved with the "Baumgarte-Shapiro-Shibata-Nakamura" formalism known as the most stable method at present. We conducted several test problems and as for the first practical test, we calculated the gravitational collapse of a 15M⊙ star. The main features found from our calculations are: (1) high-velocity bipolar outflow is driven from the proto-neutron star and moves along the rotational axis in strongly magnetized models, (2) a one-armed spiral structure appears, which originates from the low-|T/W| instability, and (3) by comparing the GRMHD and NMHD models, the maximum density increases about ̃30% in GRMHD models due to the stronger gravitational effect. These features agree very well with previous studies and our codes are thus reliable for numerical simulation of gravitational collapse of massive stars. © 2010. The American Astronomical Society.