Hypervelocity Stars. II. The Bound Population
Abstract
Hypervelocity stars (HVSs) are stars ejected completely out of the Milky Way by three-body interactions with the massive black hole in the Galactic center. We describe 643 new spectroscopic observations from our targeted survey for HVSs. We find a significant (3.5 σ) excess of B-type stars with large velocities +275 km s-1 < vrf < 450 km s-1 and distances d>10 kpc that are most plausibly explained as a new class of HVSs: stars ejected from the Galactic center on bound orbits. If a Galactic center ejection origin is correct, the distribution of HVSs on the sky should be anisotropic for a survey complete to a fixed limiting apparent magnitude. The unbound HVSs in our survey have a marginally anisotropic distribution on the sky, consistent with the Galactic center ejection picture.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2007
- DOI:
- 10.1086/513595
- arXiv:
- arXiv:astro-ph/0701600
- Bibcode:
- 2007ApJ...660..311B
- Keywords:
-
- Galaxy: Center;
- Galaxy: Halo;
- Galaxy: Kinematics and Dynamics;
- Galaxy: Stellar Content;
- Stars: Early-Type;
- Astrophysics
- E-Print:
- 8 pages, accepted to ApJ