Initial data for binary neutron stars with adjustable eccentricity
Initial data for binary neutron stars with adjustable eccentricity
复制标题
偏心率可调的双中子星的初始数据
DOI：
10.1103/physrevd.90.084043
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发表时间：
2014
影响因子：
5
通讯作者：
B. Brügman
中科院分区：
文献类型：
--
作者：
N. Moldenhauer;C. M. Markakis;N. K. Johnson-McDaniel;W. Tichy;B. Brügman
在圆形轨道上的双中子星可以被模拟为螺旋对称的，即，在旋转的框架中静止。这种对称性产生了欧拉方程的第一积分，通常用于通过迭代构造平衡解。然而，对于偏心轨道，缺乏螺旋对称性阻止了这种方法的使用，数值相对论界经常通过叠加助推的球形恒星来构建初始数据，而不需要求解欧拉方程。在这些数据的演化过程中出现的假激发的中子星星振荡是因为这种结构缺乏适当的潮汐形变，并且在线性共轨坐标系中是静止的，而不是在共轨坐标系中。我们考虑在旋转坐标系中瞬时静止的远心点的偏心构形。我们将螺旋对称的概念扩展到偏心轨道，通过使用椭圆的内切圆将每个伴星的椭圆轨道近似为瞬时圆形。这两个内接螺旋对称向量产生近似的瞬时第一积分的欧拉方程在每个同伴。我们使用这些积分的爱因斯坦约束的自洽迭代的基础上，构造共形的薄三明治的偏心二进制的初始数据。我们发现，虚假的恒星振荡减少了至少一个数量级，与叠加的初始数据的演变中发现的。潮汐引起的振荡，但是，物理和定性类似于早期的演变。最后，我们展示了如何将径向速度由于辐射反应在我们的内接螺旋对称向量，这将允许一个获得真正的noneccentric初始数据时，我们的偏心parameteris设置为零。
Binary neutron stars in circular orbits can be modeled as helically symmetric, i.e., stationary in a rotating frame. This symmetry gives rise to a first integral of the Euler equation, often employed for constructing equilibrium solutions via iteration. For eccentric orbits, however, the lack of helical symmetry has prevented the use of this method, and the numerical relativity community has often resorted to constructing initial data by superimposing boosted spherical stars without solving the Euler equation. The spuriously excited neutron star oscillations seen in evolutions of such data arise because such configurations lack the appropriate tidal deformations and are stationary in a linearly comoving—rather than rotating—frame. We consider eccentric configurations at apoapsis that are instantaneously stationary in a rotating frame. We extend the notion of helical symmetry to eccentric orbits, by approximating the elliptical orbit of each companion as instantaneously circular, using the ellipse’s inscribed circle. The two inscribed helical symmetry vectors give rise to approximate instantaneous first integrals of the Euler equation throughout each companion. We use these integrals as the basis of a self-consistent iteration of the Einstein constraints to construct conformal thin-sandwich initial data for eccentric binaries. We find that the spurious stellar oscillations are reduced by at least an order of magnitude, compared with those found in evolutions of superposed initial data. The tidally induced oscillations, however, are physical and qualitatively similar to earlier evolutions. Finally, we show how to incorporate radial velocity due to radiation reaction in our inscribed helical symmetry vectors, which would allow one to obtain truly noneccentric initial data when our eccentricity parameteris set to zero.
具有磁场的旋转和双星相对论星
DOI：
--
发表时间：
2011
期刊：
影响因子：
--
作者：
C. Markakis
通讯作者：
C. Markakis