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Order-Disorder Phase Transition in Black-Hole Star Clusters
Jihad Touma1, Scott Tremaine2, Mher Kazandjian3
1Department of Physics, American University of Beirut, PO Box 11-0236, Riad El-Solh, Beirut 11097 2020, Lebanon.
Physical Review Letters
|August 7, 2019
Summary
Galactic centers with massive black holes can transition from spherical to lopsided star clusters. This phase transition significantly increases observable transient events, like stellar flares and gravitational waves.
Area of Science:
- Astrophysics
- Computational simulations
- Galaxy evolution
Background:
- Galactic centers host massive black holes surrounded by dense star clusters.
- Cluster structure influences observable transient events, including stellar flares and gravitational waves.
- Current rate estimates often assume spherical symmetry for star clusters.
Purpose of the Study:
- To investigate the evolutionary processes of star clusters around massive black holes.
- To determine if star clusters can transition from spherical to non-spherical configurations.
- To assess the impact of cluster structure on the rate of transient astrophysical events.
Main Methods:
- Simulated generic evolutionary processes of star clusters.
- Analyzed phase transitions from thermal equilibrium to alternative states.
- Modeled the resulting orbital dynamics and orientations of stars within the cluster.
Main Results:
- Demonstrated that star clusters can undergo a robust phase transition to a lopsided equilibrium.
- Identified this lopsided state characterized by high-eccentricity, aligned stellar orbits.
- Predicted a significantly higher rate of transient events in this ordered, lopsided phase.
Conclusions:
- Star cluster evolution can lead to non-spherical, ordered structures around massive black holes.
- The transition to a lopsided equilibrium dramatically enhances the expected rate of observable transient events.
- Further research on cluster formation and evolution is crucial to determine the prevalence of ordered versus disordered cluster states.
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