The dynamics of circumbinary disk with high eccentricity binary

We investigate the tidal interaction between the circumbinary disk and the binary system with high eccentricity. Our investigation is focused on the final phase of the binary formation, when the gap between the binary star and the inner edge of the circumbinary disk is so large that the mass accretion from the circumbinary disk to the binary star is effectively terminated. From the numerical calculation with our modified SPH method specifically designed for modeling the shear flows, we have found that the m = 1 density enhancement is generated in the circumbinary disk if the eccentricity is sufficiently high. The density peak is always located at nearly 270° from the apastron of the secondary star. A simple analytical consideration shows that this standing structure is generated by the static component (l = 0 mode) of the m = 1 harmonic potential of the binary system. The interaction with (m = 1, l = 0) harmonic potential may play an important role in further mass accretion from the disk to the binary, since it enhances the eccentricity of the gas motion in the disk and provides a chance for more effective tidal interactions.