arXiv 2203.035362022-03-07gr-qcastro-ph.GA

随机引力波背景搜索和对中子星椭圆率的约束

Stochastic gravitational-wave background searches and constraints on neutron-star ellipticity

Federico De Lillo, Jishnu Suresh, Andrew L. Miller

备注：: 10 pages, 6 figures, 2 tables
DOI：: 10.1093/mnras/stac984

摘要：

在地基探测器的频段内，旋转中子星是很有希望的引力波源。由于它们偏离球面对称，预计它们将发射准单色、长持续时间的GW信号，称为连续波（CW）。这种变形的程度，以及因此关于NS的内部结构的信息，被编码在称为椭圆度的无量纲参数$\varepsilon$中。对来自孤立星系NS的CW信号的探测已经显示出对低至$\varepsilon \sim \mathcal{O}(10^{-9})$的椭圆度敏感。这些搜索对于检测和表征来自单个NS的GW是最佳的，但是它们不是被设计来测量作为总体的NS的属性，例如平均椭圆率$\varepsilon_{\mathrm{av}}$。这些集合属性可以通过测量由来自单独不可检测的NS的GW信号的叠加产生的随机引力波背景（SGWB）来确定。在这项工作中，我们使用先进的LIGO和处女座的前三个观测运行的数据进行互相关搜索这样的SGWB。没有发现SGWB信号的证据，我们对无量纲能量密度参数$Ω_{\mathrm{gw}}(f)$设置上限。使用这些结果，我们还限制银河系NS和5个NS "热点“的平均椭圆率，作为搜索$N_{\mathrm{band}}$的频带内的NS发射GW的数量的函数。我们发现银河系NS的$\varepsilon_{\mathrm{av}} \lesssim 1.8 \times 10^{-8}$和$N_{\mathrm{band}}=1.6 \times 10^7$，以及NS热点的$\varepsilon_{\mathrm{av}} \lesssim [3.5-11.8]\times 10^{-7}$和$N_{\mathrm{band}}=1.6 \times 10^{10}$。

英文摘要：

Rotating neutron stars (NSs) are promising sources of gravitational waves (GWs) in the frequency band of ground-based detectors. They are expected to emit quasi-monochromatic, long-duration GW signals, called continuous waves (CWs), due to their deviations from spherical symmetry. The degree of such deformations, and hence the information about the internal structure of a NS, is encoded in a dimensionless parameter $\varepsilon$ called ellipticity. Searches for CW signals from isolated Galactic NSs have shown to be sensitive to ellipticities as low as $\varepsilon \sim \mathcal{O}(10^{-9})$. These searches are optimal for detecting and characterising GWs from individual NSs, but they are not designed to measure the properties of NSs as population, such as the average ellipticity $\varepsilon_{\mathrm{av}}$. These ensemble properties can be determined by the measurement of the stochastic gravitational-wave background (SGWB) arising from the superposition of GW signals from individually-undetectable NSs. In this work, we perform a cross-correlation search for such a SGWB using the data from the first three observation runs of Advanced LIGO and Virgo. Finding no evidence for a SGWB signal, we set upper limits on the dimensionless energy density parameter $Ω_{\mathrm{gw}}(f)$. Using these results, we also constrain the average ellipticity of Galactic NSs and five NS ``hotspots'', as a function of the number of NSs emitting GWs within the frequency band of the search $N_{\mathrm{band}}$. We find $\varepsilon_{\mathrm{av}} \lesssim 1.8 \times 10^{-8}$, with $N_{\mathrm{band}}=1.6 \times 10^7$, for Galactic NSs, and $\varepsilon_{\mathrm{av}} \lesssim [3.5-11.8]\times 10^{-7}$, with $N_{\mathrm{band}}=1.6 \times 10^{10}$, for NS hotspots.

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