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arXiv 1208.3258astro-ph.SR
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非吸积中子星壳的力学性质

Mechanical Properties of non-accreting Neutron Star Crusts

Kelsey Hoffman, Jeremy Heyl

摘要:

中子星地壳的力学性质,如断裂应变和剪切模量,对探测来自中子星的引力波以及来自软伽马射线中继站(SGR)的爆发具有重要意义。这些属性在这里计算三种不同的地壳成分的非吸积中子星,从三个不同的冷却历史的结果,以及为纯铁地壳。利用分子动力学对地壳成分进行了简单剪切模拟。断裂应变和剪切模量在四种情况下是相似的,对于初始完美BCC晶格的模拟,在密度为ρ= 10^{14} g cm^{-3}时,断裂应变约为0.1,剪切模量约为10^{30} dyne cm^{-2}。利用这些地壳性质和{PSR J2124-3358}的观测性质,发现最大变形地壳的引力波的预测应变振幅大于LIGO的观测上限。这表明,这种情况下的中子星地壳可能没有最大限度地变形,或者它可能没有完美的BCC晶格结构。还探讨了从SGRs的爆发计算的地壳属性的影响。一个完美的体心立方晶格结构的机械性能发现,地壳事件本身不能被排除触发SGR爆发的能量。

英文摘要:

The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from Soft Gamma-ray Repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ~0.1 and a shear modulus of ~10^{30} dyne cm^{-2} at a density of ρ= 10^{14} g cm^{-3} for simulations with an initially perfect BCC lattice. With these crustal properties and the observed properties of {PSR J2124-3358} the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIGO. This suggests that the neutron star crust in this case may not be maximally deformed or it may not have a perfect BCC lattice structure. The implications of the calculated crustal properties of bursts from SGRs are also explored. The mechanical properties found for a perfect BCC lattice structure find that crustal events alone can not be ruled out for triggering the energy in SGR bursts.

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