Helium-variable star HD 184927

The spectrum of HD 184927 is found to vary from that of a normal B2 star to that of a pronounced helium-rich star, with a period of 9.48 days. Low-amplitude light variation is also present, most noticeably in the ultraviolet below the Balmer discontinuity. The helium-variable stars are shown to be intermediate in surface temperature between the hotter helium-rich stars and the cooler helium-weak stars. Within the class of helium variables, the hottest stars are helium-rich throughout their cycles; and intermediate objects vary between helium-rich and normal or helium-weak and the coolest stars are always helium-weak