Bin Liu
Room 552, Building 8, Hainayuan, West District, Zijingang Campus, Zhejiang University
Contact: liusaky@gmail.com
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I am broadly interested in the theoretical topics of merging black hole binary formation and exoplanet formation. My main research expertise lies in the dynamics of few-body systems, and for most of my research, I utilize analytical and numerical approaches to study the secular dynamics of multiple systems.
Before moving to ZJU, I was a Marie-Curie Fellow at the Niels Bohr Institute (2020-2023), Research Associate at Cornell University (2017-2020), and a postdoc fellow at Shanghai Astronomical Observatory (2016-2018). I completed my Ph.D. in Astronomy from the University of Science and Technology of China in 2016.
Research
Research
Formation of Hot Jupiters
Formation of Hot Jupiters
via Kozai migration
via Kozai migration
We systematically studied how the short-range force, such as General Relativity, tidal and rotational distortions of planets affect the extreme orbital behavior during Kozai cycles.
We found that the maximum eccentricity of the inner binary can be calculated analytically.
We present an analytical method for calculating the formation efficiency of close-in planets (e.g., Hot Jupiters) in the Kozai migration scenario.
Binary mergers in triples:
Binary mergers in triples:
unique signatures for LIGO
unique signatures for LIGO
We found important/distinct signatures produced by the tertiary-induced channal:
The spins of two black holes preferentially lie in the orbital plane when they enter the LIGO band.
Large residual eccentricity.
Small mass ratio.
Binary dynamics near a rotating supermassive black hole
Binary dynamics near a rotating supermassive black hole
We studied the general relativistic (GR) effects induced by the tertiary rotating supermassive black hole (SMBH). Such GR effects are largely ignored in most of the previous studies.
We found that the GR effects significant modify the standard Kozai-Induced merger scenario.
We showed that it is possible to probe the spins of SMBHs with gravitational waves from surrounding compact binaries.
Binary-Binary Interactions
Binary-Binary Interactions
A secular resonance between the Kozai oscillation of the inner binary and the nodal precession of the outer orbit driven by the tertiary binary may occur in the quadruple systems.
In the presence of tertiary binary, the merger fraction of the inner binary is increased to 10–30% compared to the similar triple systems.
Other applications: Formation of
WD 1856+534 b and TIC 470710327.
Secular effect in coplanar triples:
Secular effect in coplanar triples:
Apsidal Precession Resonance
Apsidal Precession Resonance
We found a novel secular resonance in a coplanar triple: apsidal precession resonance, where the apsidal precession rate of the inner binary matches that of the outer binary.
Such resonance allows efficient angular momentum exchange between the inner and outer binaries, thereby changing the orbital eccentricities.
One application: Uncovering a hidden black hole binary from secular eccentricity variations of a tertiary star.
Hierarchical mergers
Hierarchical mergers
in multiple systems
in multiple systems
We explored hierarchical mergers in multiple stellar systems, taking into account the natal kick and mass loss due to the supernova explosion on each component, as well as the merger kick received by the merger remnant.
We suggest that GW190412, GW190814, and GW190521 could be produced via hierarchical mergers in multiples, likely in a nuclear star cluster, with the final merger induced by a massive black hole.
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