The theory of binary star evolution suggests that many massive stars should lose their outer layers when they interact with a comapion star in their orbit.  This interaction should reveal hot helium-rich stars with masses ranging from about 2 to 8 times that of our Sun.  These stars are known as ‘stripped stars.’ 

My collaborators and I have discovered the first population of stripped stars, using the excess ultraviolet light they contribute to their binary system as a clue. By performing spectroscopic follow-up of stars that appeared bluewards of the main sequence we found stars that matched well with theoretical predicitions. We’ve observed radial velocity variations, indicating they are in binary systems, as well as very high temperatures, strong surface gravities, and low amounts of surface hydrogen.

These newly identified stars fill a gap in our understanding of helium-rich stars, bridging the space between subdwarfs and Wolf-Rayet stars. They are also of great importance in astrophysics because they serve as sources of ionizing radiation, may become stripped-envelope supernovae, and could be involved in the formation of merging double neutron star systems.

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