The NANOGrav 12.5-year Data Set: Search for Non-Einsteinian Polarization Modes in the Gravitational-wave Background
The NANOGrav 12.5-year Data Set: Search for Non-Einsteinian Polarization Modes in the Gravitational-wave Background
复制标题
DOI：
10.3847/2041-8213/ac401c
复制
发表时间：
2021-09
期刊：
影响因子：
--
通讯作者：
Z. Arzoumanian;P. Baker;H. Blumer;B. Bécsy;A. Brazier;P. Brook;S. Burke-Spolaor;M. Charisi
中科院分区：
文献类型：
--
作者：
Z. Arzoumanian;P. Baker;H. Blumer;B. Bécsy;A. Brazier;P. Brook;S. Burke-Spolaor;M. Charisi
我们在北美纳赫兹引力波天文台（NANOGrav）12.5年的数据集中，依据广义度量引力理论所允许的所有空间相关性来寻找引力波背景（GWB）的证据。我们在数据中没有发现支持这种相关性存在的实质性证据。我们发现标量 - 横向（ST）相关性产生的信噪比和贝叶斯因子高于四极（张量 - 横向，TT）相关性。具体而言，我们发现信噪比为2.8的ST相关性比TT相关性（赫林斯和唐斯相关性）更受青睐，贝叶斯优势约为20∶1。然而，当我们纳入太阳系星历系统误差的建模和/或完全不考虑脉冲星J0030 + 0451时，ST相关性的显著性大幅降低。即使从表面上看取其标称信噪比，对模拟数据集的分析表明，在引力波背景中仅存在通常的TT模式的情况下，观察到这样的值并非极不可能。在没有探测到任何引力极化模式的情况下，对于谱指数γ = 5和参考频率$f_{yr}=1$年⁻¹，我们对它们的振幅设定了上限。在八大类广义度量引力理论的上限中，对于包含TT和ST模式的度量时空理论族，我们得到$A_{TT}^{95\%}=(9.7\pm0.4)\times10^{-16}$以及$A_{ST}^{95\%}=(1.4\pm0.03)\times10^{-15}$。
We search NANOGrav’s 12.5 yr data set for evidence of a gravitational-wave background (GWB) with all the spatial correlations allowed by general metric theories of gravity. We find no substantial evidence in favor of the existence of such correlations in our data. We find that scalar-transverse (ST) correlations yield signal-to-noise ratios and Bayes factors that are higher than quadrupolar (tensor-transverse, TT) correlations. Specifically, we find ST correlations with a signal-to-noise ratio of 2.8 that are preferred over TT correlations (Hellings and Downs correlations) with Bayesian odds of about 20:1. However, the significance of ST correlations is reduced dramatically when we include modeling of the solar system ephemeris systematics and/or remove pulsar J0030+0451 entirely from consideration. Even taking the nominal signal-to-noise ratios at face value, analyses of simulated data sets show that such values are not extremely unlikely to be observed in cases where only the usual TT modes are present in the GWB. In the absence of a detection of any polarization mode of gravity, we place upper limits on their amplitudes for a spectral index of γ = 5 and a reference frequency of f yr = 1 yr−1. Among the upper limits for eight general families of metric theories of gravity, we find the values of ATT95%=(9.7±0.4)×10−16 and AST95%=(1.4±0.03)×10−15 for the family of metric spacetime theories that contain both TT and ST modes.