1 The shallower of the two minima in the light-curve of an eclipsing binary. It occurs when the secondary (the star of lower surface brightness) is eclipsed by the brighter primary. Depending on the relative brightness of the components, the secondary minimum of an Algol star may be either barely detectable or nearly as deep as primary minimum. In a Beta Lyrae star it is shallower, and in a W Ursae Majoris star it may be nearly as deep as the primary eclipse.
2 The dip between the double maxima of an RV Tauri star.