Distribution in the color–magnitude diagram of the periodic variables studied in this paper. Filled colored and black circles represent stars with secured periods, while open circles locate periodic variables whose periods need confirmation. Their colors identify the different groups of variable stars identified in Sect. 5. Black crosses identify eclipsing binaries. Light-gray points locate all other stars with good light curves in V′ and B′. The horizontal dashed line indicates the V′ magnitude above which periodic variables have been searched for. The location of red giant star 349 is also indicated.