2008ApJ...685L..47L

We measure the projected rotational velocities of the late B-type hypervelocity stars HVS 7 and HVS 8 from high-resolution spectroscopy to be 60±17 km/s and 260±70 km/s. The ``slow'' rotation of HVS 7 is in principle consistent with having originated in a binary system, assuming a high inclination angle of the stellar rotation axis. However, the fast rotation of HVS 8 is more typical of single B-type stars. HVS 8 could have therefore been ejected by a mechanism other than that proposed by Hills. We also estimate the effective temperatures and surface gravities for HVS 7 and HVS 8 and obtain an additional measurement of their radial velocities. We find evidence in support of a blue horizontal branch nature for HVS 7 and a main-sequence nature for HVS 8.