LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
TAPIR, Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA.
Phys Rev Lett. 2019 Sep 13;123(11):111102. doi: 10.1103/PhysRevLett.123.111102.
We analyze gravitational-wave data from the first LIGO detection of a binary black-hole merger (GW150914) in search of the ringdown of the remnant black hole. Using observations beginning at the peak of the signal, we find evidence of the fundamental quasinormal mode and at least one overtone, both associated with the dominant angular mode (ℓ=m=2), with 3.6σ confidence. A ringdown model including overtones allows us to measure the final mass and spin magnitude of the remnant exclusively from postinspiral data, obtaining an estimate in agreement with the values inferred from the full signal. The mass and spin values we measure from the ringdown agree with those obtained using solely the fundamental mode at a later time, but have smaller uncertainties. Agreement between the postinspiral measurements of mass and spin and those using the full waveform supports the hypothesis that the GW150914 merger produced a Kerr black hole, as predicted by general relativity, and provides a test of the no-hair theorem at the ∼10% level. An independent measurement of the frequency of the first overtone yields agreement with the no-hair hypothesis at the ∼20% level. As the detector sensitivity improves and the detected population of black-hole mergers grows, we can expect that using overtones will provide even stronger tests.
我们分析了首次 LIGO 探测到的二进制黑洞合并（GW150914）的引力波数据，以寻找残余黑洞的衰减。利用信号峰值开始时的观测结果，我们发现了基本准正常模式和至少一个泛音的证据，两者都与主导角模式（ℓ=m=2）相关联，置信度为 3.6σ。包括泛音的衰减模型使我们能够仅从后激发现象数据测量残余物的最终质量和自旋大小，从而获得与从完整信号推断出的值一致的估计。我们从衰减中测量到的质量和自旋值与稍后仅使用基本模式获得的值一致，但具有较小的不确定性。后激发现象中质量和自旋的测量值与使用完整波形的测量值之间的一致性支持了 GW150914 合并产生了一个 Kerr 黑洞的假设，这与广义相对论的预测一致，并以约 10%的水平检验了无毛定理。第一泛音频率的独立测量结果与无毛假设在约 20%的水平上一致。随着探测器灵敏度的提高和检测到的黑洞合并数量的增加，我们可以预期使用泛音将提供更强的测试。
