Rukbat

Rukbat (Alpha Sgr, α Sagittarii, α Sgr, Alrami) is a blue, class B dwarf star. Based on an excess emission of infrared radiation, it may have a debris disk, much like Vega.

This is a single-lined spectroscopic binary system. Alpha Sagittarii is emitting an excess flux of X-rays, which is not expected to originate from a star of this spectral class. The most likely explanation is that the companion is an active pre-main sequence star or else a star that has just reached the main sequence.