Short Period Binary Star Formation: Stimulating the Fission Model with the Addition of Large Circumstellar Disks

Abstract

The purpose of this research is to determine the validity of the fission model of short orbital period binary star formation. The fission model describes the process in which a protostar with a rapid rotation splits into two bodies which then orbit around a common center of mass. The fission model is one of the three major models currently under investigation by the wider astrophysical community as possible sources for the formation of short orbital period binary star systems. While fission has not received much attention in the last two decades due to results found in large scale numerical simulations, the advances in computational power now available allow much more complex simulations that show promise in solving this problem. Rather than looking at single stars, we are simulating the evolution of a rotating protostar with a large circumstellar disk that is approaching a reverse Roche limit, where the mass of the disk starts to pull the protostar apart. By including this large disk in our calculations, we find that the prospects for fission are greatly enhanced. We use the computer code Chymera in ACISS and Talapas, the University of Oregon high-performance computing clusters in our study to simulate the fluid dynamics of this system. Unsurprisingly, our nonlinear simulations of solitary stars show no fission occurring, but out linear simulations with large circumstellar disks show greatly decreased growth rates, allowing for the possibility for fission as these instabilities build. Our nonlinear simulations of these systems are inconclusive, but promising.