Three Dimensional Magneto Hydrodynamical Simulations of Gravitational Collapse of a 15Msun Star

TL;DR

This paper presents two advanced 3D magneto-hydrodynamical simulation codes, one Newtonian and one general relativistic, to study the gravitational collapse of a 15 solar mass star, revealing key features like bipolar outflows and spiral instabilities.

Contribution

Introduction of two new 3D MHD simulation codes, including a fully general relativistic version, for modeling massive star collapse with detailed validation and comparison.

Findings

High velocity bipolar outflows along the rotational axis.

Emergence of a one-armed spiral structure from low-|T/W| instability.

GRMHD models show ~30% higher maximum density than NMHD models.

Abstract

We introduce our newly developed two different, three dimensional magneto hydrodynamical codes in detail. One of our codes is written in the Newtonian limit (NMHD) and the other is in the 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 did several test problems and as for the first practical test, we calculated gravitational collapse of a $15M_\odot$ star. Main features found from our calculations are; (1) High velocity bipolar outflow is driven from the proto-neutronstar and moves through along the rotational axis in strongly magnetized models; (2) A one-armed spiral structure appears which is originated from the low-$|T/W|$ instability; (3) By comparing GRMHD and NMHD models, the maximum density increases about $\sim30%$ in GRMHD models due to the stronger gravitational effect. These features agree very well with previous studies and our codes are thus reliable to numerical simulation of gravitational collapse of massive stars.