24 research outputs found
The Fate of Former Companions to Hypervelocity Stars Originating at the Galactic Center
The hypervelocity star SDSS J090745.0+024507 in the halo of the Milky Way
galaxy (Brown et al. 2005) most likely originated from the breakup of a binary
star system by the central black hole, SgrA* (Hills 1988). We examine the fate
of former binary companions to similar hypervelocity stars (HVSs) by simulating
600 different binary orbits around SgrA* with a direct N-body integration code.
For some orbital parameters, the binary breakup process leads to HVSs with
ejection velocities that are almost an order of magnitude larger than the
velocity observed for SDSS J090745.0+024507. The former companion stars
populate highly eccentric orbits which resemble the observed orbits for some of
the stars nearest to SgrA*.Comment: Accepted for publication in MNRA
Triple Disruptions in The Galactic Centre: Captured and Ejected Binaries, Rejuvenated Stars, and Correlated Orbits
The disruption of a binary star by a massive black hole (MBH) typically leads
to the capture of one component around the MBH and the ejection of its
companion at a high velocity, possibly producing a hypervelocity star. The high
fraction of observed triples (% for F/G/K stars and % for OB
stars) give rise to the possibility of the disruption of triples by a MBH. Here
we study this scenario, and use direct -body integrations to follow the
orbits of thousands of triples, during and following their disruption by a MBH
(of M, similar to the MBH existing in the Galactic
Centre; SgrA). We find that triple disruption can lead to several outcomes
and we discuss their relative frequency. Beside the ejection/capture of single
stars, similar to the binary disruption case, the outcomes of triple disruption
include the ejection of hypervelocity binaries; capture of binaries around the
MBH; collisions between two or all of the triple components (with low enough
velocities that could lead to their merger); and the capture of two or even
three stars at close orbits around the MBH. The orbits of single stars captured
in a single disruption event are found to be correlated. The eccentricity of
the mutual orbits of captured/ejected binaries is typically excited to higher
values. Stellar evolution of captured/ejected binaries may later result in
their coalescence/strong interaction and the formation of hypervelocity blue
stragglers or merger remnants in orbits around SgrA*. Finally, the capture of
binaries close to the MBH can replenish and increase the binary frequency near
the MBH, which is otherwise very low.Comment: 8 pages, 2 figures, 3 tables, submitted to MNRA