We report the discovery of a 16 ^ { th } magnitude star , ( catalog HE 0437 $ - $ 5439 ) , with a heliocentric radial velocity of +723 \pm 3 { km s ^ { -1 } } .
A quantitative spectral analysis of high-resolution optical spectra obtained with the VLT and the UVES spectrograph shows that HE 0437 - 5439 is a main sequence B-type star with T _ { eff } =20 350 K , \log ( g ) = 3.77 , solar within a factor of a few helium abundance and metal content , rotating at v \sin ( i ) = 54 { km s ^ { -1 } } .
Using appropriate evolutionary tracks we derive a mass of 8 ~ { } M _ { \sun } and a corresponding distance of 61 kpc .
Its galactic rest frame velocity is at least 563 { km s ^ { -1 } } , almost twice the local Galactic escape velocity , indicating that the star is unbound to the Galaxy .
Numerical kinematical experiments are carried out to constrain its place of birth .
It has been suggested that such hyper-velocity stars can be formed by the tidal disruption of a binary through interaction with the super-massive black hole at the Galactic center ( GC ) .
HE 0437 - 5439 needs about 100 Myrs to travel from the GC to its present position , much longer than its main sequence lifetime of 25 Myrs .
This can only be reconciled if HE 0437 - 5439 is a blue straggler star .
In this case , the predicted proper motion is so small that it can only be measured by future space missions .
Since the star is much closer to the Large Magellanic Cloud ( LMC , 18 kpc ) than to the GC , it can reach its position from the center of the LMC .
The proper motion predicted in this case is about 2 { mas yr ^ { -1 } } ( relative to the LMC ) , large enough to be measurable with conventional techniques from the ground .
The LMC origin could also be tested by a high-precision abundance analysis .