Systematic Search for Blue Hypervelocity Stars from LAMOST Survey

• Published in: The Astrophysical journal Vol. 986; no. 1; pp. 22 - 38
• Main Authors: Sun, Yongkang, Huang, Yang, Liu, Jifeng, Fu, Haozhu, Zhang, Huawei, Li, Yinbi, Du, Cuihua, Shi, Jianrong, Kong, Xiao
• Format: Journal Article
• Language: English
• Published: The American Astronomical Society 10.06.2025; IOP Publishing
• Subjects: Early-type stars; Hypervelocity stars; Radial velocity; Sky surveys
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/adcebe

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 multibody 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 10 new unbound B- and A-type HVS candidates (designated LAMOST-HVS 5 through LAMOST-HVS 14), tripling the number of unbound HVSs previously identified by LAMOST. Kinematic analyses suggest that these newly discovered HVS candidates likely originated either from the GC 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.