GW190521 formation via three-body encounters in young massive star clusters
Abstract
GW190521 is the most massive binary black hole (BBH) merger observed to date, and its primary component lies in the pair-instability (PI) mass gap. Here, we investigate the formation of GW190521-like systems via three-body encounters in young massive star clusters. We performed 2 × 105 simulations of binary-single interactions between a BBH and a massive $\ge {60}\,$M⊙ black hole (BH), including post-Newtonian terms up to the 2.5 order and a prescription for relativistic kicks. In our initial conditions, we take into account the possibility of forming BHs in the PI mass gap via stellar collisions. If we assume that first-generation BHs have low spins, $\sim {0.17}{{\ \rm per\ cent}}$ of all the simulated BBH mergers have component masses, effective and precessing spin, and remnant mass and spin inside the $90{{\ \rm per\ cent}}$ credible intervals of GW190521. Seven of these systems are first-generation exchanged binaries, while five are second-generation BBHs. We estimate a merger rate density $\mathcal {R}_{\rm GW190521}\sim {0.03}\,$Gpc$^{-3}\,$yr-1 for GW190521-like binaries formed via binary-single interactions in young star clusters. This rate is extremely sensitive to the spin distribution of first-generation BBHs. Stellar collisions, second-generation mergers and dynamical exchanges are the key ingredients to produce GW190521-like systems in young star clusters.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2021
- DOI:
- 10.1093/mnras/stab2783
- arXiv:
- arXiv:2105.12757
- Bibcode:
- 2021MNRAS.508.3045D
- Keywords:
-
- gravitational waves;
- black hole physics;
- methods: numerical;
- stars: black holes;
- stars: kinematics and dynamics;
- galaxies: star clusters: general;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics;
- General Relativity and Quantum Cosmology
- E-Print:
- 11 pages, 4 figures, MNRAS