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arXiv · 2406.00923

A high-velocity star recently ejected by an intermediate-mass black hole in M15

Yang Huang·Qingzheng Li·Jifeng Liu·Xiaobo Dong·Huawei Zhang·Youjun Lu·Cuihua Du
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Abstract

The existence of intermediate-mass black holes (IMBHs) is crucial for understanding various astrophysical phenomena, yet their existence remains elusive, except for the LIGO-Virgo detection. We report the discovery of a high-velocity star J0731+3717, whose backward trajectory about 21 Myr ago intersects that of globular cluster M15 within the cluster tidal radius. Both its metallicity [Fe/H] and its alpha-to-iron abundance ratio [$\alpha$/Fe] are consistent with those of M15. Furthermore, its location falls right on the fiducial sequence of the cluster M15 on the color-absolute magnitude diagram, suggesting similar ages. These support that J0731+3717 is originally associated with M15 at a confidence level of "seven nines". We find that such a high-velocity star ($V_{\rm ej} = 548^{+6}_{-5}$ km s$^{-1}$) was most likely tidally ejected from as close as one astronomical unit to the center of M15, confirming an IMBH ($\ge 100 M_{\odot}$ with a credibility of 98%) as the exclusive nature of the central unseen mass proposed previously.

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Yang Huang, Qingzheng Li, Jifeng Liu, Xiaobo Dong, Huawei Zhang, Youjun Lu, Cuihua Du. 2024-06-03. A high-velocity star recently ejected by an intermediate-mass black hole in M15. https://arxiv.org/abs/2406.00923

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