The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background
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DOI：
10.3847/2041-8213/acdac6
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发表时间：
2023-06
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通讯作者：
G. Agazie;A. Anumarlapudi;A. Archibald;Z. Arzoumanian;P. Baker;B. Bécsy;L. Blecha;A. Brazier;P. Brook;S. Burke-Spolaor;R. Burnette;R. Case;M. Charisi;S. Chatterjee;K. Chatziioannou;B. Cheeseboro;Siyuan Chen;T. Cohen;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;C. Cutler;M. DeCesar;D. DeGan;P. Demorest;Heling Deng;T. Dolch;B. Drachler;J. Ellis;E. Ferrara;W. Fiore;E. Fonseca;G. Freedman;N. Garver-Daniels;P. Gentile;K. A. Gersbach;J. Glaser;D. Good;K. Gultekin;J. Hazboun;S. Hourihane;K. Islo;R. Jennings;A. Johnson;Megan L. Jones;A. Kaiser;D. Kaplan;L. Kelley;M. Kerr;J. Key;T. C. Klein;N. Laal;M. Lam;W. Lamb;T. Lazio;N. Lewandowska;T. Littenberg;Tianyu Liu;A. Lommen;D. Lorimer;Jing Luo;R. Lynch;Chung-Pei Ma;D. Madison;M. A. Mattson;A. McEwen;J. McKee;M. Mclaughlin;N. McMann;B. W. Meyers;P. Meyers;C. Mingarelli;A. Mitridate;P. Natarajan;C. Ng;D. Nice;S. Ocker;K. Olum;T. Pennucci;B. Perera;P. Petrov;N. Pol;H. Radovan;S. Ransom;P. Ray;J. Romano;S. C. Sardesai;A. Schmiedekamp;C. Schmiedekamp;K. Schmitz;L. Schult;B. Shapiro-Albert;X. Siemens;J. Simon;M. Siwek;I. Stairs;D. Stinebring;K. Stovall;Jerry P. Sun;A. Susobhanan;J. Swiggum;Jacob M. Taylor;S. Taylor;J. E. Turner;C. Unal;M. Vallisneri;R. V. Haasteren;S. Vigeland;H. Wahl;Qiaohong Wang;C. Witt;O. Young
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作者：
G. Agazie;A. Anumarlapudi;A. Archibald;Z. Arzoumanian;P. Baker;B. Bécsy;L. Blecha;A. Brazier;P. Brook;S. Burke-Spolaor;R. Burnette;R. Case;M. Charisi;S. Chatterjee;K. Chatziioannou;B. Cheeseboro;Siyuan Chen;T. Cohen;J. Cordes;N. Cornish;F. Crawford;H. Cromartie;K. Crowter;C. Cutler;M. DeCesar;D. DeGan;P. Demorest;Heling Deng;T. Dolch;B. Drachler;J. Ellis;E. Ferrara;W. Fiore;E. Fonseca;G. Freedman;N. Garver-Daniels;P. Gentile;K. A. Gersbach;J. Glaser;D. Good;K. Gultekin;J. Hazboun;S. Hourihane;K. Islo;R. Jennings;A. Johnson;Megan L. Jones;A. Kaiser;D. Kaplan;L. Kelley;M. Kerr;J. Key;T. C. Klein;N. Laal;M. Lam;W. Lamb;T. Lazio;N. Lewandowska;T. Littenberg;Tianyu Liu;A. Lommen;D. Lorimer;Jing Luo;R. Lynch;Chung-Pei Ma;D. Madison;M. A. Mattson;A. McEwen;J. McKee;M. Mclaughlin;N. McMann;B. W. Meyers;P. Meyers;C. Mingarelli;A. Mitridate;P. Natarajan;C. Ng;D. Nice;S. Ocker;K. Olum;T. Pennucci;B. Perera;P. Petrov;N. Pol;H. Radovan;S. Ransom;P. Ray;J. Romano;S. C. Sardesai;A. Schmiedekamp;C. Schmiedekamp;K. Schmitz;L. Schult;B. Shapiro-Albert;X. Siemens;J. Simon;M. Siwek;I. Stairs;D. Stinebring;K. Stovall;Jerry P. Sun;A. Susobhanan;J. Swiggum;Jacob M. Taylor;S. Taylor;J. E. Turner;C. Unal;M. Vallisneri;R. V. Haasteren;S. Vigeland;H. Wahl;Qiaohong Wang;C. Witt;O. Young
我们报告了来自北美纳赫兹引力波天文台收集的15年脉冲星定时数据集的67颗脉冲星之间随机信号的多条证据。这种相关性遵循随机引力波背景的赫灵斯-唐斯模式。这种具有幂律谱的引力波背景的存在比只有独立脉冲星噪声且贝叶斯因子超过1014的模型更有利，而且这种模型比具有200-1000贝叶斯因子的不相关的普通幂律谱模型更有利，这取决于光谱建模的选择。我们使用一种从数据集中去除脉冲星间相关性的方法建立了后一种贝叶斯因子的统计背景分布，发现在零不相关情况下，观察到的贝叶斯因子的p = 10−3（≈3σ）。直接建立脉冲星间相关加权和的频率检验统计量得到p = 5 × 10−5至1.9 × 10−4（≈3.5σ-4σ）。假设一个适用于双超大质量黑洞吸气系综的基准f−2/3特征应变谱，在参考频率为1年−1时，应变振幅为2.4−0.6+0.7×10−15（中位数+ 90%可信区间）。推断出的引力波背景振幅和频谱与天体物理学对超大质量黑洞双星群信号的预期一致，尽管不能排除更多的奇异宇宙和天体物理学来源。对Hellings-Downs相关性的观察指出了这个信号的引力波起源。
We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings–Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 1014, and this same model is favored over an uncorrelated common power-law spectrum model with Bayes factors of 200–1000, depending on spectral modeling choices. We have built a statistical background distribution for the latter Bayes factors using a method that removes interpulsar correlations from our data set, finding p = 10−3 (≈3σ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of interpulsar correlations yields p = 5 × 10−5 to 1.9 × 10−4 (≈3.5σ–4σ). Assuming a fiducial f −2/3 characteristic strain spectrum, as appropriate for an ensemble of binary supermassive black hole inspirals, the strain amplitude is 2.4−0.6+0.7×10−15 (median + 90% credible interval) at a reference frequency of 1 yr−1. The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings–Downs correlations points to the gravitational-wave origin of this signal.