Be stars


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Be stars

(bee-ee ) Irregular variables of spectral type B in which bright emission lines of hydrogen are superimposed on the normal absorption spectrum. They are now known to be identical to shell stars. Some Be stars are young stars, rather more massive than Ae stars: together they are sometimes classed as Herbig Ae-Be stars, and are heavier versions of the T Tauri stars. These Be stars are rotating very rapidly and are slowly losing mass to an expanding shell that surrounds the star and is drawn into a disk around the equator due to the rotation. Other Be stars are in close binary systems, with shells that consist of gas being accreted from an evolved companion star (see mass transfer).
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