The geometry of the eclipsing X-ray binary problem
This diagram illustrates the geometry of the system. The observer, on
Earth, views X-rays from the binary system. Most of the X-rays are emitted
by the smaller star (whose orbital path is shown in black), which orbits
the central star (denoted by a yellow dot in the diagram), but the central
star is also a source of some X-rays. If the plane of the binary system is
the same as that of the binary system and the observer, then the X-ray
emitter can be eclipsed by the central star.
To simplify the problem, we make two assumptions when we use this
- The orbit of the X-ray emitting star is circular and its
velocity is constant.
- The orbit of the observed star is large and the system is
distant, so that light rays from the source are parallel.
- The plane of the binary system is at 90 degrees, edge on to our line of sight. (The actual orbit is at 83 degrees.)