1. Dynamical Dances of Black Holes
  2. The Final Flight of a Binary Neutron Star

Dynamical Dances of Black Holes

The following simulations show gravitational-wave captures that results from the encounter of four black holes, which can occur at the cores of dense stellar systems such as gloublar clusters. Such encounters can lead to long-lived “resonating” interactions, through which many temporary binary systems are created. When one correctly includes post-Newtonian terms in the equations of motion, the formation of a highly eccentric binary can lead to a rapid inspiral and merge due to gravitational wave emission zapping orbital energy. These mergers can maintain their high eccentricies into the LIGO sensitive frequency range and occur at a rate accessible by advanced LIGO. If detected, such systems will highly constrain their formation scenario and be a clear indicator that dynamics can play a key role in facilitating binary black hole mergers. Examples below are from Zevin et al. 2019a (ApJ 871, 1).

The Final Flight of a Binary Neutron Star

The following animation shows the kinematic evolution of a simulated double neutron star system that may have been the progenitor of GW170817. Using the observed offset of GW170817 from its host galaxy (NGC 4993), we can constrain aspects of the stellar evolutionary process that led to its formation. The pair of stars—a neutron star and a normal star—orbit quietly, until the normal star undergoes a supernova, spawning a second neutron star and “kicking” the system into an elliptical orbit. The two neutron stars eventually merge and generate gravitational waves, a gamma-ray burst, and an explosion called a kilonova. Other potential lives are shown in the thinner, lighter-colored lines. Data for this animation comes from the analysis in Abbott et al. 2017 (ApJ 850L, 40A).

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