binary system (e.g., Hillier et al. 2006).

It is generally agreed that the orbital plane lies in the equatorial plane of the bipolar structure$-$the Homunculus, such that the inclination angle (the angle between a line perpendicular to the orbital plane and the line of sight) is $i=42$ (Davidson et al. 2001; Smith 2002). However, there is a disagreement about the orientation of the semimajor axis in the orbital plane$-$the periastron longitude. We will use the commonly used periastron longitude angle $\omega$: $\omega=0^\circ$ for a case when the secondary is toward the observer at an orbital angle of $90^\circ$ before periastron, and so on, as summarized in equation (\[eq:omega\]), $$\label{eq:omega}
\omega =
  \begin{cases}
~~0^\circ & \qquad  {\rm secondary~toward~observer~}90^\circ~{\rm before~periastron}
    \\
~90^\circ & \qquad  {\rm secondary~toward~observer~at~periastron}
    \\
180^\circ & \qquad  {\rm secondary~toward~observer~}90^\circ~{\rm after~periastron}
    \\
270^\circ & \qquad  {\rm secondary~toward~observer~at~apastron}.
 \end{cases}$$

While some groups argue that the secondary (less massive) star is away from us during periastron passages, $\omega=270^\circ$ (e.g., Nielsen et al. 2007; Damineli et al. 2008), others argue that the secondary is toward us during periastron passages, $\omega=90^\circ$ (Falceta-Gonçalves et al. 2005; Abraham et al. 2005; Kashi & Soker 2007, who use the angle $\gamma=90^\circ-\omega$). Other semimajor axis orientations have also 