Be stars are B stars that show emissions lines in their spectra. The emission lines are thought to come from a disk of material that surrounds the star and may be associated with B stars that are rapidly rotating.

Be stars with neutron star companions are often transient X-ray sources, and are the so-called Be Xray binaries.

One celebrated Be star is the binary companion of PSR B1259-63, a pulsar that orbits the star in an eccentric orbit every three and a half years. During periastron the pulsar disappears and the source flares in the radio.