An X-Ray View of Hypervelocity Star HVS5

Hypervelocity stars (HVSs) are a new class of objects traveling in the Galactic halo at velocities �400-750 km s−1 (unbound to the Milky Way), most of which are main sequence B-type stars. We identified an interesting hypervelocity star (HVS 5; minimum velocity of 663 km s−1 in the Galactic rest frame) that shows cometary optical morphology (Figure 1), suggesting a tail behind a fast moving object. We propose a 60 ks Chandra ACIS-S observation of HVS 5 to search for X-ray emission from gas swept by the star and shock heated to high temperature. Our goal is to learn about the shock speed and the ambient medium in which HVSs are traveling. In the case of non-detection, we can still place constraint on the mass loss rate.