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arXiv 0901.3258gr-qcastro-ph.HE
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用引力波观测测量中子星状态方程

Measuring the neutron star equation of state with gravitational wave observations

Jocelyn S. Read, Charalampos Markakis, Masaru Shibata, Koji Uryu, Jolien D. E. Creighton, John L. Friedman

摘要:

我们报告的第一项研究的结果,使用数值模拟来估计的精度,可以使用引力波观测的双中子星螺旋测量参数的中子星状态方程。模拟使用Shibata和Uryu的演化和初始数据代码来计算中子星的最后几个轨道和合并,物质由参数化状态方程描述。以前的工作建议使用一个有效的截止频率来限制状态方程。然而,我们发现,更大的精度是通过测量偏离点粒子的重力波形在后期inspiral期间产生的限制。当恒星接近最后的俯冲和合并时,中子星的致密性(中子星的质量与半径之比)越小,引力波相的积累就越快。我们估计,现实的状态方程将导致引力波形,是区别于点粒子在一个有效的距离(距离一个最佳取向和定位系统,将产生一个等效的波形振幅)100 Mpc或less. As Lattimer和Prakash观察到,中子星的半径是密切相关的压力,在密度不远高于核。我们的研究结果表明,频率在500和1000 Hz之间的宽带引力波观测将限制这种压力,我们估计它可以测量的精度。有关半径可测性的初步估计表明,在100 Mpc时,半径的精确度可以达到~1 km。

英文摘要:

We report the results of a first study that uses numerical simulations to estimate the accuracy with which one can use gravitational wave observations of double neutron star inspiral to measure parameters of the neutron-star equation of state. The simulations use the evolution and initial-data codes of Shibata and Uryu to compute the last several orbits and the merger of neutron stars, with matter described by a parametrized equation of state. Previous work suggested the use of an effective cutoff frequency to place constraints on the equation of state. We find, however, that greater accuracy is obtained by measuring departures from the point-particle limit of the gravitational waveform produced during the late inspiral. As the stars approach their final plunge and merger, the gravitational wave phase accumulates more rapidly for smaller values of the neutron star compactness (the ratio of the mass of the neutron star to its radius). We estimate that realistic equations of state will lead to gravitational waveforms that are distinguishable from point particle inspirals at an effective distance (the distance to an optimally oriented and located system that would produce an equivalent waveform amplitude) of 100 Mpc or less. As Lattimer and Prakash observed, neutron-star radius is closely tied to the pressure at density not far above nuclear. Our results suggest that broadband gravitational wave observations at frequencies between 500 and 1000 Hz will constrain this pressure, and we estimate the accuracy with which it can be measured. Related first estimates of radius measurability show that the radius can be determined to an accuracy of ~1 km at 100 Mpc.

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