Binary star systems are not rare. Neither are systems where one star is a remnant like a white dwarf or neutron star, and its companion is on the main sequence.

In those systems, the dense remnant can draw material away from the main sequence star. This can create violent Type 1a supernovae in the case of a white dwarf, and the emission of extremely powerful x-rays in the case of a neutron star.

In new research, astronomers observed the cataclysmic variable binary star V Sagittae (V Sge). It's extremely bright for its type, indicating that the accretor star is drawing an enormous amount of material from the donor, which gathers on the surface of the accretor before igniting and flaring brightly.

The research is "V Sge: Supersoft Source or Exotic Hot Binary? I. An X-Shooter campaign in the high state. The lead author is Pasi Hakala from the Finnish Centre for Astronomy with ESO.

V Sge has a main sequence star with about 3.3 solar masses, which is the donor star in the pair. The other star is the accretor, and while astronomers thought it was a white dwarf for a long time, more recent observations suggest that it's a Wolf-Rayet star, which are closely related to white dwarfs. V Sge is unusual and has puzzled astronomers for decades.

"V Sagittae is no ordinary star system – it's the brightest of its kind and has baffled experts since it was first discovered in 1902," said Professor Phil Charles from Southampton University, who was involved with the study. 

Source:Universetoday