Light curves of the best candidates as function of phase. (a) Algol (closed circles), (b) λ Tau (open diamonds), (c) ζ Gem (closed triangles), (d) l Car (closed squares), (e) β Lyr (open circles), (f) η Aql (open squares), and (g) δ Cep (open triangles). (h) All curves in the same scale: Algol is more than one magnitude brighter than the other six variables and has the largest amplitude.