Constraints on the origins of hypervelocity stars: velocity distribution, mergers and star-formation history

Abstract

In recent years surveys have identified several dozen B stars in the Milky Way halo moving faster than the local escape speed. The origin of most of these hypervelocity stars (HVSs) is still poorly constrained. Here we show that the velocity distribution, and in particular the deficiency in >700 km/s HVSs is inconsistent with binary disruptions by the massive black hole (MBH) in the Galactic Centre. This conclusion holds in the full and empty loss cone regime, and for secular instabilities in eccentric disks. Accounting for multiple close encounters between binaries and the MBH, does not qualitatively change the results. Moreover, there is no observed counterpart population in the Galactic Centre that is consistent with the HVSs. The star-formation history could be tuned explain the HVS velocity distribution, but this tuning would produce a mismatch with the observed HVS flight times. Frequent stellar collisions of the binary components due to interactions with the MBH do not significantly impact the velocity distribution in the Galactic halo. Such collisions, however, can leave observable remnants in the Galactic Centre, and potentially explain the origins of G2-like dust clouds.

11 pages, 10 figures, accepted to MNRAS. This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review. The version of record [MNRAS, 513, 4257] is available online at DOI:10.1093/mnras/stac1108

References in corpus (25)

• galpy: A Python Library for Galactic Dynamics
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• An Update on Monitoring Stellar Orbits in the Galactic Center
• Starbursts near supermassive black holes: young stars in the Galactic Center, and gravitational waves in LISA band
• Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities
• Twelve years of spectroscopic monitoring in the Galactic Center: the closest look at S-stars near the black hole
• Detection of Galactic Center source G2 at 3.8 $\mu$m during periapse passage
• An Alternative Origin for Hypervelocity Stars
• Secular Evolution Of Binaries Near Massive Black Holes: Formation of compact binaries, merger/collision products and G2-like objects
• A population of dust-enshrouded objects orbiting the Galactic black hole
• Hypervelocity stars and the environment of Sgr A*
• Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
• 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
• The Anisotropic Spatial Distribution of Hypervelocity Stars
• The Nature of the Hyper-Runaway Candidate HIP 60350
• The Hills Mechanism and the Galactic Center S-stars
• Hypervelocity stars from young stellar clusters in the Galactic Centre
• Gaia EDR3 in 6D: Searching for unbound stars in the Galaxy
• The Nearest High-Velocity Stars Revealed by LAMOST Data Release 1
• Hypervelocity Stars in the Gaia era. Revisiting the most extreme stars from the MMT survey
• Mapping the Galactic centre's dark cluster via Resonant Relaxation
• Forming Young and Hypervelocity Stars in the Galactic Centre via Tidal Disruption of a Molecular Cloud
• A stream of hypervelocity stars from the Galactic Center
• Ejection of Hyper-Velocity Stars from the Galactic Centre by Intermediate-Mass Black Holes

Cited by in corpus (7)

• Quasi-periodic eruptions from mildly eccentric unstable mass transfer in galactic nuclei
• Hyper-runaway and hypervelocity white dwarf candidates in \textit{Gaia} Data Release 3: possible remnants from Ia/Iax supernova explosions or dynamical encounters
• On the origins of extreme velocity stars as revealed by large-scale Galactic surveys
• Runaway and Hypervelocity Stars from Compact Object Encounters in Globular Clusters
• Searching for a Hypervelocity White Dwarf Companion: A Proper Motion Survey of SN 1006
• A Recent Supermassive Black Hole Binary in the Galactic Center Unveiled by the Hypervelocity Stars
• Black Hole Survival Guide: Searching for Stars in the Galactic Center That Endure Partial Tidal Disruption