Year: 2003
Type: article
Abstract: We study three processes that eject hypervelocity (>10 3 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, R 0 = 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 a b ≲ 0.3 AU. For solar mass stars, the corresponding number of hypervelocity stars within the solar radius is ~60(η/0.1)( a b /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 ~10 3 . Hypervelocity stars may be detectable by the next generation of large-scale optical surveys.
Source: The Astrophysical Journal
DOI: 10.1086/379546
Authors: Qingjuan Yu, Scott Tremaine
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2153555990