Image of light curve of an eclipsing binary with description

This light curve seems really weird to me, I'm used to seeing light curves where the barycenter is a straight line. It either stays at a place, moves at a constant speed or slowly increases its speed. But here it looks like the barycenter periodically changes its speed. Why is this happening? Can someone please explain the details of this graph.

  • 1
    $\begingroup$ Is there a third star in the system that could be causing additional fluctuations, or is it just these two stars? $\endgroup$
    – HDE 226868
    Jul 29, 2018 at 19:39
  • $\begingroup$ As a minor bugbear, I'm used to a light curve being brightness vs time, so I wouldn't call this a light curve. That said, I'm with @HDE226868: it looks like there's a third body. I had thought that it might be something about the Earth's motion around the Sun but the period isn't right. $\endgroup$
    – Warrick
    Jul 30, 2018 at 7:21
  • $\begingroup$ If there's a third body, it could be a supermassive blackhole. Or something really massive compared to the other two. $\endgroup$ Aug 8, 2018 at 16:36
  • $\begingroup$ You question is about a screen shot of some source you haven't cited. Please retype the text as actual text so that the question is more easily searchable and vision-impaired community members can read it with a screen reader, and so that the context of the question can be researched by anyone interested. Thanks! $\endgroup$
    – uhoh
    Apr 21, 2021 at 20:58