Kavli Affiliate: Huawei Zhang
| First 5 Authors: Yongkang Sun, Yang Huang, Jifeng Liu, Haozhu Fu, Huawei Zhang
| Summary:
Hypervelocity stars (HVSs) represent a unique class of objects capable of
escaping the gravitational pull of the Milky Way due to extreme acceleration
events, such as close encounters with the supermassive black hole at the
Galactic center (GC), supernova explosions in binary systems, or multi-body
dynamical interactions. Finding and studying HVSs are crucial to exploring
these ejection mechanisms, characterizing central black holes, probing the GC
environment, and revealing the distribution of dark matter in our galaxy. The
Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)
spectroscopic surveys have so far identified four B-type unbound HVSs. To
expand this sample with the second-phase LAMOST survey that started in 2018, we
conducted a systematic search for early-type HVSs using the LAMOST Data Release
10. We identified 125 early-type high-velocity candidates with total velocities
exceeding 300 km,s$^{-1}$. Among them, we report ten new unbound B- and A-type
hypervelocity star (HVS) candidates (designated LAMOST-HVS5 through
LAMOST-HVS14), tripling the number of unbound HVSs previously identified by
LAMOST. Kinematic analyses suggest that these newly discovered HVS candidates
likely originated either from the Galactic Center or via dynamical
interactions. Future high-resolution follow-up observations promise to refine
the stellar parameters, distances, and elemental abundances of these
candidates, thereby providing deeper insights into their origins and broadening
their potential applications across astrophysics.
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