Some young , massive stars can be found in the Galactic halo .
As star formation does not occur in the halo , they must have been formed in the disk and been ejected shortly afterwards .
One explanation is a supernova in a tight binary system .
The companion is ejected and becomes a runaway star .
HD 271791 is the kinematically most extreme runaway star known ( galacic restframe velocity 725 \pm 195 km s ^ { -1 } even greater than the Galactic escape velocity ) .
Moreover , an analysis of the optical spectrum showed an enhancement of the \alpha -elements .
This indicates an origin in a supernova .
As such high velocities are not reached in classical binary supernova scenarii , a very massive but compact primary , probably of Wolf-Rayet type is required .
The star is a perfect candidate for studying nucleosynthesis in a core-collapse supernova because of the contamination of its surface layers with supernova ejecta of its former very massive primary .
The goal of this project is to determine the abundances of a large number of elements from the \alpha -process , the iron group , and heavier elements by a quantitative spectral analysis from the optical and the UV with detailed stellar atmosphere models that account for deviations from the local thermal equilibrium ( NLTE ) .
We intent to verify whether core-collapse supernova are a site of r-process element production .
Here , we state the current status of the project .