We present the first numerical study of gravitational waves (GWs) from collapsar disks, using state-of-the-art 3D general relativistic magnetohydrodynamic simulations of collapsing stars. These simulations incorporate a fixed Kerr metric for the central black hole (BH) and employ simplified prescriptions for disk cooling. We find that cooled disks with an expected scale height ratio of H/R ≳ 0.1 at ∼10 gravitational radii induce Rossby instability in compact, high-density rings. The trapped Rossby vortices generate vigorous coherent emission regardless of disk magnetization and BH spin. For BH mass of ∼10 M _⊙, the GW spectrum peaks at ∼100 Hz, with some breadth due to various nonaxisymmetric modes. The spectrum shifts toward lower frequencies as the disk viscously spreads and the circularization radius of the infalling gas increases. Weaker-cooled disks with H/R ≳ 0.3 form a low-density extended structure of spiral arms, resulting in a broader, lower-amplitude spectrum. Assuming an optimistic detection threshold with a matched-filter signal-to-noise ratio of 20 and a rate similar to Type Ib/c supernovae, LIGO–Virgo–KAGRA (LVK) could detect ≲1 event annually, suggesting that GW events may already be hidden in observed data. Third-generation GW detectors could detect dozens to hundreds of collapsar disks annually, depending on the cooling strength and the disk formation rate. The GW amplitudes from collapsar disks are ≳100 times higher with a substantially greater event rate than those from core-collapse supernovae, making them potentially the most promising burst-type GW class for LVK and Cosmic Explorer. This highlights the importance of further exploration and modeling of disk-powered GWs, promising insights into collapsing star physics.

中文翻译：

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在 LIGO 的视野中？来自冷却的塌缩星盘的强烈相干引力波


我们使用最先进的 3D 广义相对论磁流体动力学模拟坍缩恒星，首次对来自坍缩星盘的引力波 (GW) 进行了数值研究。这些模拟结合了中心黑洞 (BH) 的固定克尔度量，并采用简化的磁盘冷却方案。我们发现，在约 10 个引力半径处，预期尺度高度比为 H/R ≳ 0.1 的冷却圆盘会在致密、高密度环中引起罗斯贝不稳定性。无论圆盘磁化强度和 BH 自旋如何，捕获的罗斯比涡旋都会产生强烈的相干发射。对于 ∼10 M _⊙的 BH 质量，引力波谱在 ∼100 Hz 处达到峰值，由于各种非轴对称模式而具有一定的宽度。随着圆盘粘性扩散和落入气体的圆化半径增加，频谱向较低频率移动。 H/R ≳ 0.3 的弱冷却盘形成低密度延伸的旋臂结构，从而产生更宽、更低振幅的频谱。假设匹配滤波器信噪比为 20 的乐观检测阈值和类似于 Ib/c 型超新星的速率，LIGO–Virgo–KAGRA (LVK) 每年可以检测到 ≲1 个事件，这表明 GW 事件可能已经隐藏在观测数据中。第三代引力波探测器每年可以探测到数十到数百个塌陷盘，具体取决于冷却强度和塌陷盘形成速率。塌陷星盘的引力波振幅比核心塌缩超新星的引力波振幅高 ≳100 倍，事件发生率也高得多，这使它们成为 LVK 和宇宙探索者最有希望的爆发型引力波类别。这凸显了进一步探索和建模磁盘驱动的引力波的重要性，有望为塌缩恒星物理提供深入的见解。