Astronomers at the University of Leeds have shown that the disk-enclosed Be stars are probably formed in triple star systems, rather than binary systems as previously thought. These “vampire” stars absorb matter from their neighbors and rotate, giving them their unique properties.
Be stars are a subtype of massive and bright stars of spectral class B. One of its features is the strong hydrogen emission line in the spectrum. The source of this radiation is thought to be a disk of ionized gas that surrounds and “flows” from the Be star.
For astronomers, these objects serve as a kind of laboratory bed for developing and testing theories about star formation. Therefore, although the mechanics of those disks are well studied, their formation remains a mystery. Most scientists cling to the theory that the reason is the rapid rotation that astronomers have seen in almost all objects in this group. But why do these stars rotate so fast? He has three possible mechanisms. First, the molecular cloud in which the star formed may have rotated. Second, the rotation can be caused by compression of the star’s core. Eventually, the star may begin to rotate through interaction with her second object in the binary system. If the third option is correct, this should somehow be reflected in the statistics of the occurrence of B and Be stars in binary systems, the authors of the new study suggested.
By observing how a particular star moves over time, we can determine whether it has a companion star. If the orbit is straight, then the star is “solitary”, but if it oscillates slightly or at most spirals, then the star has at least one “neighbor”. “When we applied this estimation method to two groups of stars, B stars and Be stars, we found that at first glance, Be stars have fewer companion stars than B stars.” “This is interesting because we expected to see a companion,” explained Jonathan Dodd, a PhD student at the University of Leeds, UK, and one of the authors of the new paper. The study was published in Monthly Notices, a monthly journal of the Royal Astronomical Society.
source: https://academic.oup.com/mnras/article/527/2/3076/7310873?login=false