Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter
Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter
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DOI：
10.1103/physrevd.104.063003
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发表时间：
2021-06
影响因子：
5
通讯作者：
I. Legred;K. Chatziioannou;R. Essick;Sophia Han;P. Landry
中科院分区：
文献类型：
--
作者：
I. Legred;K. Chatziioannou;R. Essick;Sophia Han;P. Landry
PSR J0740+6620是已知质量最大的脉冲星，利用NICER和xmm -牛顿天文台的数据，最近对其半径进行了测量。我们采用基于高斯过程的非参数EoS模型，并结合其他x射线、射电和引力波对中子星的观测信息，研究了这一测量对中子星状态方程（EoS）的影响。我们的分析略微不利于质量-半径关系中支持分离的混合星分支的eos，这是强相变的代理，贝叶斯因子为$6.9$。对于这样的eos，从强子到杂化分支的跃迁质量被限制在外部（$1,2$） $M_{\odot}$。我们还发现，在中子星核心内部，共形声速界限被打破，这意味着核心物质是强相互作用的。声速的平方在$3.60^{+2.25}_{-1.89}$乘以核饱和密度时达到最大值$0.75^{+0.25}_{-0.24}\, c^2$% credibility. Since all but the gravitational-wave observations prefer a relatively stiff EoS, PSR J0740+6620's central density is only $3.57^{+1.3}_{-1.3}$ times nuclear saturation, limiting the density range probed by observations of cold, nonrotating neutron stars in $\beta$-equilibrium.
X-ray pulse profile modeling of PSR J0740+6620, the most massive known pulsar, with data from the NICER and XMM-Newton observatories recently led to a measurement of its radius. We investigate this measurement's implications for the neutron star equation of state (EoS), employing a nonparametric EoS model based on Gaussian processes and combining information from other x-ray, radio and gravitational-wave observations of neutron stars. Our analysis mildly disfavors EoSs that support a disconnected hybrid star branch in the mass-radius relation, a proxy for strong phase transitions, with a Bayes factor of $6.9$. For such EoSs, the transition mass from the hadronic to the hybrid branch is constrained to lie outside ($1,2$) $M_{\odot}$. We also find that the conformal sound-speed bound is violated inside neutron star cores, which implies that the core matter is strongly interacting. The squared sound speed reaches a maximum of $0.75^{+0.25}_{-0.24}\, c^2$ at $3.60^{+2.25}_{-1.89}$ times nuclear saturation density at 90% credibility. Since all but the gravitational-wave observations prefer a relatively stiff EoS, PSR J0740+6620's central density is only $3.57^{+1.3}_{-1.3}$ times nuclear saturation, limiting the density range probed by observations of cold, nonrotating neutron stars in $\beta$-equilibrium.