Beta Lyrae variable

The two component stars of Beta Lyrae systems are quite heavy (several solar masses (M☉) each) and extended (giants or supergiants).

In close binary systems such as beta Lyrae systems, a second effect reinforces this mass loss: when a giant star swells, it may reach its Roche limit, that is, a mathematical surface surrounding the two components of a binary star where matter may freely flow from one component to the other.

Calculations show that its mass loss then will become so large that in a comparatively very short time (less than half a million years) this star, that was once the heaviest, now becomes the lighter of the two components.

The light curves of beta Lyrae variables are quite smooth: eclipses start and end so gradually that the exact moments are impossible to define.

In beta Lyrae systems with periods longer than 100 days one of the components is generally a supergiant.