• DOI:10.1086/379546
• Corpus ID: 315189

Ejection of Hypervelocity Stars by the (Binary) Black Hole in the Galactic Center

@article{Yu2003EjectionOH,
  title={Ejection of Hypervelocity Stars by the (Binary) Black Hole in the Galactic Center},
  author={Qingjuan Yu and Scott Tremaine},
  journal={The Astrophysical Journal},
  year={2003},
  volume={599},
  pages={1129 - 1138}
}

• Qingjuan Yu, S. Tremaine
• Published 3 September 2003
• Physics, Geology
• The Astrophysical Journal

We study three processes that eject hypervelocity (>103 km s-1) stars from the Galactic center: (1) close encounters of two single stars, (2) tidal breakup of binary stars by the central black hole, as originally proposed by Hills, and (3) three-body interactions between a star and a binary black hole (BBH). Mechanism 1 expels hypervelocity stars to the solar radius, R0 = 8 kpc, at a negligible rate, ~10-11 yr-1. Mechanism 2 expels hypervelocity stars at a rate ~10-5(η/0.1) yr-1, where η is the fraction of stars in binaries with semimajor axis ab ≲ 0.3 AU. For solar mass stars, the corresponding number of hypervelocity stars within the solar radius is ~60(η/0.1)(ab/0.1 AU)1/2. For mechanism 3, Sgr A* is assumed to be one component of a BBH. We constrain the allowed parameter space (semimajor axis, mass ratio) of the BBH. In the allowed region (for example, a semimajor axis of 0.5 × 10-3 pc and a mass ratio of 0.01), the rate of ejection of hypervelocity stars can be as large as ~10-4 yr-1, and the expected number of hypervelocity stars within the solar radius can be as large as ~103. Hypervelocity stars may be detectable by the next generation of large-scale optical surveys.