Oral Presentation

Magnetic-Field-Induced Inspiral of Protostellar Binaries Accreting from a Circumbinary Disk

Author(s): Tomoaki Matsumoto (Hosei University), Kenta Hotokezaka (University of Tokyo), Kohei Inayoshi (Peking University)

Presenter: Tomoaki Matsumoto (Hosei University)

The orbital evolution of protostellar binaries is a key process in shaping multiple-star systems. We study the role of magnetic fields using high-resolution three-dimensional magnetohydrodynamic simulations of a binary accreting gas from an infalling envelope, analogous to the collapse of magnetized molecular cloud cores.

The simulations reveal outflows from both circumstellar disks and the circumbinary disk, together with magnetorotational instability in the circumbinary disk. These magnetic processes efficiently transport angular momentum and drive binary orbital decay, while a purely hydrodynamical model shows orbital expansion. The decay rate reaches approximately 0.3–0.7% per orbital period, depending on the initial magnetic field strength.

Our results suggest that magnetic angular momentum transport offers an efficient pathway for forming close protostellar binaries, including close twin systems whose mass ratios approach unity through circumbinary accretion.