[论文解读] Recognizing black holes in gravitational-wave observations: Telling apart impostors in mass-gap binaries

Sayak Datta, K. S. Phukon+1 more|arXiv (Cornell University)|Apr 13, 2020

Pulsars and Gravitational Waves Research被引用 9

一句话总结

该论文提出一种贝叶斯方法，通过在双星旋近过程中探测潮汐加热特征，以区分黑洞与黑洞替代物或中子星。该方法识别出仅在存在视界时才非零的波形参数，从而可检测质量间隙双星中质量最小的黑洞或质量最大的中子星。

ABSTRACT

We show how by careful monitoring of the inspiral signal from a compact object binary in ground-based gravitational wave (GW) detectors one can test if its components are black holes or not. Here we limit ourselves to black holes (with and without spin) in General Relativity. Such objects are characterized by horizons, which absorb gravitational radiation from the orbit during their inspiral in a binary, via a phenomenon known as tidal heating. By contrast, a compact object such as a neutron star has minimal tidal heating -- but has tidal deformation -- and affects the phase evolution of binaries containing it in a distinctly different way. Here we identify waveform parameters that characterize the strength of tidal heating, and are zero when there is no horizon absorption. We demonstrate how by using those parameters Bayesian methods can distinguish the presence or absence of horizons in a binary. This is a particularly exciting prospect owing to several claims that these stellar-mass objects, with masses heavier than those of neutron stars, may not have a horizon but may be black hole mimickers or exotic compact objects. Perhaps more significant is the possibility that our method can be used to test the presence or absence of horizons in mass-gap binaries and, thereby, help detect the heaviest neutron star or the lightest black hole. A proper accounting of tidal heating in binary waveform models will also be critical for an unbiased measurement of characteristics of the equation of state of neutron stars in GW observations of binaries containing them -- or even to probe the existence of exotic compact objects.

研究动机与目标

• 开发一种方法，以检验引力波信号中致密天体是否为具有视界的真正黑洞，或为其他奇异替代物。
• 通过引力波形解决在恒星级‘质量间隙’（介于中子星与黑洞之间）中识别天体的模糊性。
• 通过引入潮汐加热效应改进波形模型，以避免对中子星状态方程参数测量产生偏差。
• 通过双星旋近过程中视界吸收特征的信号，实现对质量最小黑洞或质量最大中子星的探测。
• 基于波形参数的贝叶斯推断，提供一种可检验视界存在与否的标准。

提出的方法

• 识别量化潮汐加热的波形参数，其与视界吸收成正比，并在无视界时为零。
• 建立包含潮汐加热效应的双星旋近相位演化模型，将其与中子星的潮汐形变区分开。
• 利用贝叶斯推断，基于观测到的引力波信号，比较包含与不包含视界吸收的波形模型的似然性。
• 构建一个参数空间，其中视界吸收效应仅在黑洞中非零，从而实现与替代物的统计区分。
• 在波形模型中纳入黑洞双星的自旋效应，以在真实条件下保持准确性。
• 校准该方法，使其对质量间隙中中子星与黑洞之间的过渡区域（视界形成尚不明确）保持敏感。

实验结果

研究问题

• RQ1 双星旋近过程中的潮汐加热能否作为致密天体视界形成的决定性特征？
• RQ2 贝叶斯推断如何利用引力波相位演化区分黑洞与黑洞替代物？
• RQ3 哪些波形参数对视界吸收敏感，可用于检验事件视界的有无？
• RQ4 信号中潮汐加热效应在多大程度上影响对中子星状态方程参数的测量？
• RQ5 该方法能否探测质量间隙双星中的质量最小黑洞或质量最大中子星？

主要发现

• 潮汐加热是黑洞中视界吸收的唯一特征，中子星或无视界的致密天体中均不存在。
• 所提出的量化潮汐加热的波形参数在无视界时为零，提供了清晰的判别依据。
• 对这些参数的贝叶斯分析可实现引力波数据中黑洞与替代物的统计区分。
• 该方法对质量间隙中中子星与黑洞边界区域足够敏感。
• 准确建模潮汐加热对避免从双星信号中对中子星状态方程参数测量产生偏差至关重要。
• 该方法为利用地基引力波探测器直接检验致密双星系统中黑洞假说提供了有效途径。