Speaker
Description
The orbital decay of binary systems is a key process in the formation of close binaries. We perform high-resolution three-dimensional magnetohydrodynamic (MHD) simulations of a binary system accreting gas from the surrounding environment. Our simulations reveal the presence of outflows and jets launched from both the circumstellar disks (CSDs) and the circumbinary disk (CBD). Magnetorotational instability (MRI) is also excited within the CBD. These magnetic processes efficiently extract orbital angular momentum from the binary, leading to orbital decay, whereas a purely hydrodynamical model shows orbital expansion. The decay rate reaches up to ~1% per orbital period, depending on the accretion rate onto each binary component. In the later stages, orbital decay slows down because the accumulation of magnetic flux suppresses accretion onto the stars; since both mass and angular momentum accretion drive the orbital evolution, the decay ceases as accretion halts. We discuss the possibility that magnetic fields can induce orbital decay and contribute to the formation of close binary systems.
