Key Information

• Authors: Song Wang, Xinlin Zhao, Fabo Feng, Hongwei Ge, Yong Shao, Yingzhen Cui, Shi-Jie Gao, Lifu Zhang, Pei Wang, Xue Li, Zhongrui Bai, Hailong Yuan, Yang Huang, Haibo Yuan, Zhixiang Zhang, Tuan Yi, Maosheng Xiang, Zhenwei Li, Tanda Li, Junbo Zhang, Meng Zhang, Henggeng Han, Dongwei Fan, Xiang-Dong Li, Xuefei Chen, Zhengwei Liu, Xiangcun Meng, Qingzhong Liu, Haotong Zhang, Wei-Min Gu, Jifeng Liu
• Journal: Nature Astronomy
• Year: 2024
• DOI: 10.1038/s41550-024-02359-9
• NASA ADS: 2024NatAs…8.1583W
• arXiv: 2409.06352

Abstract

The 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 a supernova explosion can more easily disrupt binaries with lower-mass black holes. Although recent Laser Interferometer Gravitational-Wave Observatory 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 non-interacting and without X-ray emission, and can be searched for using radial-velocity and astrometric methods. Here we report on Gaia Data Release 3 (DR3) 3425577610762832384, which is a wide binary system that includes a red giant star and an unseen object, exhibiting an orbital period of approximately 880 days and a near-zero eccentricity. Through the combination of radial-velocity measurements from the Large Aperture Multi-Object Spectroscopic Telescope and astrometric data from Gaia DR2 and DR3 catalogues, we determine a mass of 3 .6_‒0.5^+0.8M_☉ <![CDATA[\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3.{6}_{-0.5}^{+0.8} {M}_{\odot }$$]]> of the unseen component. If the unseen companion is a black hole, its mass would fall within the gap and it would strongly suggest 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.