The eccentric-orbit binary model for the transient X-ray sources

Eccentric-orbit binary models for transient X-ray sources are investigated. In these models, a compact star is in an eccentric orbit around a more massive star. As the compact star accretes mass from the stellar wind of the massive star, the accretion rate becomes time-dependent. The accretion rate is determined by Bondi's accretion radius, which depends on both the relative velocity of the stellar wind to the compact star and the sound velocity through the stellar wind. With reasonable sets of the eccentricity, the semi-major axis, the stellar wind velocity and the sound velocity, we obtain the variations of the light curves compatible with observations for the transient X-ray sources. It is likely that many transient X-ray sources are explainable by eccentric-orbit binary models.