# In LIGO's Sight? Vigorous Coherent Gravitational Waves from Cooled Collapsar Disks

**Authors:** Ore Gottlieb, Amir Levinson, Yuri Levin  
**arXiv:** [2406.19452](https://arxiv.org/abs/2406.19452)  
**Date:** 2024-06-27  
**Summary page:** https://www.summarizepaper.com/en/paper/2406.19452v1/

## Key points

- Groundbreaking study on gravitational waves (GWs) emitted from collapsar disks using 3D general-relativistic magnetohydrodynamic simulations
- Cooled disks with $H/R\gtrsim0.1$ trigger Rossby instability, leading to formation of trapped Rossby vortices emitting coherent GWs
- GW spectrum peaks at around $100\,{\rm Hz}$ for BH masses around $10\,M_\odot`, shifting towards lower frequencies as disk viscously spreads
- Weaker-cooled disks with $H/R\gtrsim0.3$ exhibit low-density extended structure and broader but lower-amplitude GW spectrum
- Results suggest potential detection by advanced detectors like LIGO-Virgo-KAGRA (LVK), with third-generation detectors capable of detecting dozens to hundreds of collapsar disks annually
- Collapsar disk GW amplitudes over 100 times higher than those from core-collapse supernovae, making them promising for future observatories like Cosmic Explorer

## Summary

In this groundbreaking study, the authors present the first numerical investigation of gravitational waves (GWs) emitted from collapsar disks using cutting-edge 3D general-relativistic magnetohydrodynamic simulations of collapsing stars. By incorporating a fixed Kerr metric for the central black hole (BH) and employing simplified cooling prescriptions for the disk, the researchers uncover fascinating insights into the dynamics of these systems. The simulations reveal that cooled disks with a scale height ratio of $H/R\gtrsim0.1$ at approximately 10 gravitational radii trigger Rossby instability in compact, high-density rings within the disk. This instability leads to the formation of trapped Rossby vortices that generate vigorous coherent emission, irrespective of the disk's magnetization and BH spin. For BH masses around $10\,M_\odot$, the GW spectrum peaks at around $100\,{\rm Hz}$ with some variability due to different non-axisymmetric modes. As the disk viscously spreads and the circularization radius of infalling gas expands, the spectrum shifts towards lower frequencies. Furthermore, weaker-cooled disks with $H/R\gtrsim0.3$ exhibit a low-density extended structure characterized by spiral arms, resulting in a broader but lower-amplitude GW spectrum. are generated by massive objects moving through space-time and have been predicted by Einstein's theory of general relativity. In this study, , which are formed from collapsing stars and surrounded by intense magnetic fields and hot plasma jets, are investigated through advanced numerical simulations using . The results show that cooled disks with a specific scale height ratio trigger , leading to the formation of trapped vortices that emit strong and coherent GWs. The researchers estimate that these events could potentially be detected by advanced detectors such as LIGO-Virgo-KAGRA (LVK), suggesting that they may already be present in observed data. Looking ahead, third-generation GW detectors have the potential to detect dozens to hundreds of collapsar disks each year, depending on factors such as cooling strength and disk formation rate. Importantly, GW amplitudes from collapsar disks are over 100 times higher with a significantly greater event rate compared to those from core-collapse supernovae, making them a promising burst-type class for LVK and future observatories like Cosmic Explorer. This study underscores the importance of further exploration and modeling of disk-powered GWs as it offers valuable insights into collapsing star physics. The findings presented here pave the way for enhanced understanding and detection capabilities in studying these intriguing astrophysical phenomena.