Constraints on the Dense Matter Equation of State and Neutron Star Properties from NICER’s Mass–Radius Estimate of PSR J0740+6620 and Multimessenger Observations
Constraints on the Dense Matter Equation of State and Neutron Star Properties from NICER’s Mass–Radius Estimate of PSR J0740+6620 and Multimessenger Observations
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DOI：
10.3847/2041-8213/ac089a
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
G. Raaijmakers;S. K. Greif;K. Hebeler;T. Hinderer;S. Nissanke;A. Schwenk;T. E. Riley;A. Watts
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作者：
G. Raaijmakers;S. K. Greif;K. Hebeler;T. Hinderer;S. Nissanke;A. Schwenk;T. E. Riley;A. Watts
近年来，通过分析来自射电/X射线脉冲星、引力波事件和核物理约束的多信使数据，我们对中子星的致密物质状态方程(EOS)的理解有了显著的提高。在这里，我们研究了联合估计的PSR J0740+6620的质量和半径对状态方程的额外影响，这是Riley等人提出的。通过分析来自NICER和XMM-牛顿的X射线望远镜的组合数据集。我们采用了两种不同的高密度状态方程参数化：分段多变(PP)模型和基于中子星(CS)声速的模型。在核密度下，这与基于手征有效场理论(EFT)相互作用的中子物质的微观计算有关。除了这颗重中子星的新的更好的数据外，我们还分别研究了PSR J0740+6620的射电定时质量测量，GW190425和GW170817双中子星的引力波事件，以及后者的相关konova AT2017gfo的约束。结合PSRJ0030+0451较好的质量半径估计，我们发现一颗1.4M⊙中子星的半径约为95%的可信范围：12.33−0.81+0.76 km(PP模型)和12.18−0.79+0.56 km(CS模型)。此外，我们对不同的手征EFT计算进行了探索，结果表明，新的更好的结果为中子星物质在两倍饱和密度附近的压强提供了严格的约束，这表明了这些观测在中等密度下约束致密物质相互作用的能力。
In recent years our understanding of the dense matter equation of state (EOS) of neutron stars has significantly improved by analyzing multimessenger data from radio/X-ray pulsars, gravitational wave events, and from nuclear physics constraints. Here we study the additional impact on the EOS from the jointly estimated mass and radius of PSR J0740+6620, presented in Riley et al. by analyzing a combined data set from X-ray telescopes NICER and XMM-Newton. We employ two different high-density EOS parameterizations: a piecewise-polytropic (PP) model and a model based on the speed of sound in a neutron star (CS). At nuclear densities these are connected to microscopic calculations of neutron matter based on chiral effective field theory (EFT) interactions. In addition to the new NICER data for this heavy neutron star, we separately study constraints from the radio timing mass measurement of PSR J0740+6620, the gravitational wave events of binary neutron stars GW190425 and GW170817, and for the latter the associated kilonova AT2017gfo. By combining all these, and the NICER mass–radius estimate of PSR J0030+0451, we find the radius of a 1.4 M ⊙ neutron star to be constrained to the 95% credible ranges 12.33−0.81+0.76km (PP model) and 12.18−0.79+0.56km (CS model). In addition, we explore different chiral EFT calculations and show that the new NICER results provide tight constraints for the pressure of neutron star matter at around twice saturation density, which shows the power of these observations to constrain dense matter interactions at intermediate densities.