Baumann Daniel, Bertone Gianfranco, Stout John, Tomaselli Giovanni Maria
Gravitation Astroparticle Physics Amsterdam (GRAPPA), University of Amsterdam, Amsterdam 1098 XH, Netherlands.
Center for Theoretical Physics, National Taiwan University, Taipei 10617, Taiwan.
Phys Rev Lett. 2022 Jun 3;128(22):221102. doi: 10.1103/PhysRevLett.128.221102.
Gravitational waves (GWs) are an exciting new probe of physics beyond the standard models of gravity and particle physics. One interesting possibility is provided by the so-called "gravitational atom," wherein a superradiant instability spontaneously forms a cloud of ultralight bosons around a rotating black hole. The presence of these boson clouds affects the dynamics of black hole binary inspirals and their associated GW signals. In this Letter, we show that the binary companion can induce transitions between bound and unbound states of the cloud, effectively "ionizing" it, analogous to the photoelectric effect in atomic physics. The orbital energy lost in this process can overwhelm the losses due to GW emission, so that ionization drives the inspiral rather than merely perturbing it. We show that the ionization power contains sharp features that lead to distinctive "kinks" in the evolution of the emitted GW frequency. These discontinuities are a unique signature of the boson cloud, and observing them would not only constitute a detection of the ultralight boson itself, but also provide direct information about its mass and the state of the cloud.
引力波（GWs）是超越引力和粒子物理标准模型的令人兴奋的新物理探测手段。一种有趣的可能性由所谓的“引力原子”提供，其中超辐射不稳定性会在旋转黑洞周围自发形成超轻玻色子云。这些玻色子云的存在会影响黑洞双星合并的动力学及其相关的引力波信号。在本信函中，我们表明双星伴星可诱导云的束缚态和非束缚态之间的跃迁，有效地将其“电离”，这类似于原子物理中的光电效应。在此过程中损失的轨道能量可能超过引力波发射造成的损失，从而使电离驱动合并过程而非仅仅对其产生扰动。我们表明电离功率包含尖锐特征，这些特征会导致所发射引力波频率演化中出现独特的“扭折”。这些不连续性是玻色子云的独特标志，观测到它们不仅将构成对超轻玻色子本身的探测，还将提供有关其质量和云状态的直接信息。
