Fr.: phénomène Be
The episodic occurrence of abrupt → mass loss in → Be stars resulting in → Balmer lines in emission and → infrared excess. The Be phenomenon results from a combination of a long-term secular effect and short-term instabilities, such as pulsation. The secular evolution brings the star close enough to the critical → break-up velocity, so that the additional velocity field due to the instability may allow some mass ejection (Maeder 2011).