US 708

The star is a high speed rotating, dense helium star which is supposed to be formed by the interaction of a companion star nearby

US 708 is a hyper-velocity sdO/B Ursa major in the halo of the Milky way 

 grouped into those with strong Helium lines, termed He-sdO

C.D.S. - SIMBAD4 rel 1.3 - 2015.09.30CEST14:28:41

Spectral type:

SDO D 2006ApJS..167...40E

https://en.wikipedia.org/wiki/US_708

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