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arXiv · 2409.06352

A potential mass-gap black hole in a wide binary with a circular orbit

Wang Song·Zhao Xinlin·Feng Fabo·Ge Hongwei·Shao Yong·Cui Yingzhen·Gao Shijie·Zhang Lifu·Wang Pei·Li Xue·Bai Zhongrui·Yuan Hailong·Huang Yang·Yuan Haibo·Zhang Zhixiang·Yi Tuan·Xiang Maosheng·Li Zhenwei·Li Tanda·Zhang Junbo·Zhang Meng·Han Henggeng·Fan Dongwei·Li Xiangdong·Chen Xuefei·Liu Zhengwei·Meng Xiangcun·Liu Qingzhong·Zhang Haotong·Gu Wei-Min·Liu Jifeng
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Abstract

Mass distribution of black holes identified through X-ray emission suggests a paucity of black holes in the mass range of 3 to 5 solar masses. Modified theories have been devised to explain this mass gap, and it is suggested that natal kicks during supernova explosion can more easily disrupt binaries with lower mass black holes. Although recent LIGO observations reveal the existence of compact remnants within this mass gap, the question of whether low-mass black holes can exist in binaries remains a matter of debate. Such a system is expected to be noninteracting without X-ray emission, and can be searched for using radial velocity and astrometric methods. Here we report Gaia DR3 3425577610762832384, a wide binary system including a red giant star and an unseen object, exhibiting an orbital period of approximately 880 days and near-zero eccentricity. Through the combination of radial velocity measurements from LAMOST and astrometric data from Gaia DR2 and DR3 catalogs, we determine a mass of $3.6^{+0.8}_{-0.5}$ $M_{\odot}$ of the unseen component. This places the unseen companion within the mass gap, strongly suggesting the existence of binary systems containing low-mass black holes. More notably, the formation of its surprisingly wide circular orbit challenges current binary evolution and supernova explosion theories.

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Wang Song, Zhao Xinlin, Feng Fabo, Ge Hongwei, Shao Yong, Cui Yingzhen, Gao Shijie, Zhang Lifu, Wang Pei, Li Xue, Bai Zhongrui, Yuan Hailong, Huang Yang, Yuan Haibo, Zhang Zhixiang, Yi Tuan, Xiang Maosheng, Li Zhenwei, Li Tanda, Zhang Junbo, Zhang Meng, Han Henggeng, Fan Dongwei, Li Xiangdong, Chen Xuefei, Liu Zhengwei, Meng Xiangcun, Liu Qingzhong, Zhang Haotong, Gu Wei-Min, Liu Jifeng. 2024-09-10. A potential mass-gap black hole in a wide binary with a circular orbit. https://doi.org/10.1038/s41550-024-02359-9

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