Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities

Abstract

The disruption of binary stars by the tidal field of the black hole in the Galactic Center can produce the hypervelocity stars observed in the halo. We use numerical models to simulate the full spectrum of observable velocities of stars ejected into the halo by this binary disruption process. Our model includes a range of parameters for binaries with 3-4 M_Solar primaries, consideration of radial orbits of the ejected stars through an approximate mass distribution for the Galaxy, and the impact of stellar lifetimes. We calculate the spectrum of ejection velocities and reproduce previous results for the mean ejection velocity at the Galactic center. The model predicts that the full population of ejected stars includes both the hypervelocity stars with velocities large enough to escape from the Galaxy and a comparable number of ejected, but bound, stars of the same stellar type. The predicted median speeds of the population of ejected stars as a function of distance in the halo are consistent with current observations. Combining the model with the data also shows that interesting constraints on the properties of binaries in the Galactic Center and on the mass distribution in the Galaxy can be obtained even with modest samples of ejected stars.

26 pages, including 6 figures, accepted for publication in the Astrophysical Journal

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Cited by in corpus (16)

• Hypervelocity Stars: From the Galactic Center to the Halo
• An Alternative Origin for Hypervelocity Stars
• Dynamical evolution of the young stars in the Galactic center: N-body simulations of the S-stars
• Hypervelocity Stars III. The Space Density and Ejection History of Main Sequence Stars from the Galactic Center
• Runaway and hypervelocity stars in the Galactic halo: Binary rejuvenation and triple disruption
• Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
• Hypervelocity stars and the environment of Sgr A*
• Production of Hypervelocity Stars through Encounters with Stellar-Mass Black Holes in the Galactic Centre
• Dynamical and evolutionary constraints on the nature and origin of hypervelocity stars
• Hypervelocity Collisions of Binary Stars at the Galactic Centre
• Hyperfast pulsars as the remnants of massive stars ejected from young star clusters
• Hypervelocity Stars from the Andromeda Galaxy
• Hypervelocity A & B Stars should be slow rotators
• The nature of hypervelocity stars as inferred from their galactic trajectories
• Stellar Relaxation Processes Near the Galactic Massive Black Hole
• The HYPERMUCHFUSS Campaign -- an undiscovered high velocity population