论文标题
中子星F模式和G模式振荡的通用关系
Universal Relations for Neutron Star F-Mode and G-Mode Oscillations
论文作者
论文摘要
在中子恒星的各种振荡模式中，最可能在二进制中子恒星合并中观察到F-和G-模式。已知F模式在正常中子星中与它们的潮汐变形性，惯性矩和四极力矩相关。使用分段的多面参数化方案来对不确定的HADRONIC高密度EOS进行建模，并使用恒定的声速方案来对纯夸克物质进行建模，我们完善了这种相关性，并表明这些通用关系也适用于自结界的恒星和含有相变的混合星。我们确定了F模式的新型1节点分支，该分支发生在狭窄的质量范围内的低质量杂种恒星中，超出了相变出的临界质量。这个1节点分支显示出与我们发现的通用相关性最大但仍然很小的偏差。 G模式频率仅在涉及温度，化学势或成分的状态非 - 北极方程中存在物质，或者在正交物质中的相变。因此，G模式可以用作研究杂交恒星中相变的探针。与F模式相反，不连续性G模式频率在过渡时强烈取决于过渡（不连续性的密度和大小）的性质。施加因果关系和最大质量约束，发现杂交恒星中的G模式频率的上限约为1.25 kHz。但是，如果在高于相变密度的密度下的内核中的声速C_S仅限于C_S^2 <c^2/3，则G模式频率只能达到约0.8 kHz，显着低于F模式频率，即1.3-2.8 kHz。同样，与F模式阻尼时间为0.1-1 s相比，G模式引力阻尼时间非常长，具有C_S^2 <c^{2/3}（C^2）的内核中> 10^4 s（10^2 s）。
Among the various oscillation modes of neutron stars, f- and g- modes are the most likely to be ultimately observed in binary neutron star mergers. The f-mode is known to correlate in normal neutron stars with their tidal deformability, moment of inertia and quadrupole moment. Using a piecewise polytropic parameterization scheme to model the uncertain hadronic high-density EOS and a constant sound-speed scheme to model pure quark matter, we refine this correlation and show that these universal relations also apply to both self-bound stars and hybrid stars containing phase transitions. We identify a novel 1-node branch of the f-mode that occurs in low-mass hybrid stars in a narrow mass range just beyond the critical mass necessary for a phase transition to appear. This 1-node branch shows the largest, but still small, deviations from the universal correlation we have found. The g-mode frequency only exists in matter with a non-barotropic equation of state involving temperature, chemical potential or composition, or a phase transition in barotropic matter. The g-mode therefore could serve as a probe for studying phase transitions in hybrid stars. In contrast with the f-mode, discontinuity g-mode frequencies depend strongly on properties of the transition (the density and the magnitude of the discontinuity) at the transition. Imposing causality and maximum mass constraints, the g-mode frequency in hybrid stars is found to have an upper bound of about 1.25 kHz. However, if the sound speed c_s in the inner core at densities above the phase transition density is restricted to c_s^2 < c^2/3, the g-mode frequencies can only reach about 0.8 kHz, which are significantly lower than f-mode frequencies, 1.3-2.8 kHz. Also, g-mode gravitational wave damping times are extremely long, >10^4 s (10^2 s) in the inner core with c_s^2< c^{2/3} (c^2), in comparison with the f-mode damping time, 0.1-1 s.
