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A wide star-black-hole binary system from radial-velocity measurements
Jifeng Liu1,2,3, Haotong Zhang4, Andrew W Howard5
1Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China. jfliu@nao.cas.cn.
Nature
|November 29, 2019
Summary
Astronomers discovered a massive black hole using radial-velocity measurements of a companion star. This finding challenges current stellar evolution theories for black hole formation in high-metallicity environments.
Area of Science:
- Astrophysics
- Stellar Evolution
- Black Hole Physics
Background:
- Stellar-mass black holes are typically identified via X-ray emissions from accreting gas in binary systems.
- Existing X-ray identified systems represent a minority of the total star-black hole binary population.
- Non-accreting black holes can be detected by observing the motion of their companion stars.
Purpose of the Study:
- To detect and characterize stellar-mass black holes not identified through X-ray emissions.
- To investigate the population of star-black hole binaries beyond X-ray observations.
- To test theories of stellar evolution and black hole formation.
Main Methods:
- Conducted radial-velocity measurements of the Galactic B-type star LB-1 over two years.
- Analyzed the orbital motion of the B star and its accompanying Hα emission line.
- Calculated the mass of the dark companion based on the observed stellar motion.
Main Results:
- Identified a dark companion with a mass of approximately 70 solar masses, consistent with a black hole.
- Determined the system to be a wide binary with a long orbital period of 78.9 days.
- The detected black hole mass is similar to those found in gravitational-wave experiments.
Conclusions:
- The discovery of a massive black hole via radial-velocity measurements expands the methods for detecting these objects.
- The formation of such a massive black hole in a high-metallicity environment presents a significant challenge to current stellar evolution models.
- This finding suggests that massive black holes may be more common than previously thought, particularly in wide binary systems.
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