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peaked emission lines via the doppler effect. Line structure frequently evolves on timescales of  weeks-to-years, reflecting changes in the density distribution of the disk.  There are 3 leading theories for Be-star equatorial disk formation. Firstly, \cite{porter1996} Firstly,\cite{Porter1996}  showed that all Be stars are (and normal B stars are not) rotating at or close to their break-up velocities, thus matter could more easily flow from the stellar envelope into the equatorial plane. Secondly, quasi-periodic oscillations have frequently been observed in Be stars, and these have been  suggested as a mechanism for coupling the stars' spin (angular momentum) to the outflow REF  Thirdly, binary companions have been suggested to stimulate disk-formation by lowering the effective gravity at