Introduction

Recently, my research interest has been mainly on Be/X-ray binaries and colliding wind binaries. Included in the following pages are the results from SPH simulations of these objects.

Be/X-ray binaries

For the past ~10 years, I've been working on Be/X-ray binaries. In the first several years, with Ignacio Negueruela, I've made semi-analytical studies on the disk radius around the Be star in Be/X-ray binaries, taking into account the tidal/resonant torque by the neutron star companion. We have shown that, by the tidal/resonant interaction with the neutron star, the Be-star disk is truncated at a radius depending on the orbital parameters, and proposed that it is the structure and evolution of the truncated Be disk that controls the X-ray activity of Be/X-ray binaries. For overview of the Be/X-ray binaries, click on the "Be/X-Ray Binaries: Overview" button in the left frame.

Since October 2000, I've been working on the numerical study of the interaction between the Be-star disk and the neutron star in Be/X-ray binaries, using a Smoothed Particle Hydrodynamics (or SPH) code developed by Matthew Bate and his colleagues. The first of a series of papers with Matthew Bate, Gordon Ogilvie and Jim Pringle was publied in MNRAS and is available at:

This paper confirmed the tidal truncation scenario of Be disks proposed by Ignacio and myself. It also showed how the Be disk evolves under the influence of the neutron star in an eccentric orbit.

Recently, with Kimitake Hayasaki, I have also studied the accretion process onto the neutron star in Be/X-ray binaries. Some results have been/will be published in MNRAS, and are also available at :

Besides these papers, we have published our results in several proceedings papers.

To see simulation results including movies, click on "Be/X simulations" button in the left frame.

Colliding wind binaries

In late January 2007, I participated in a stimulating mini-workshope on eta Carinae, held at Bartol Research Institute, University of Delaware, USA. At the end of the workshop, Stan Owocki suggested me to run SPH simulations of colliding winds in eta Car. At the time, I was not sure that it was a good idea. But it soon turned out that the simulation results greatly helped us understand the 3-D structure of the coliding winds in this system. I have presented the first result from these simulations at the IAU Symp. 250 on Massive Stars as Cosmic Engines (astro-ph/0803.3977). More detailed results were recently submitted to MNRAS Letters.

I have also carried out several simulations for other objects such as WR 140 and LS I +61 303. Take a look at the "Colliding wind simulations" pages that include movies from simulations of eta Car and other interacting binaries.

[ Be/X-ray binaries | Colliding wind binaries ]