arXiv 1506.014452015-06-04astro-ph.SRastro-ph.HEnucl-th

故障期间中子星壳核耦合的观测约束

Observational constraints on neutron star crust-core coupling during glitches

William G. Newton, Sabrina Berger, Brynmor Haskell

备注：: 12 pages, 7 figures, 2 tables; submitted to MNRAS
DOI：: 10.1093/mnras/stv2285

摘要：

我们表明，观测到的船帆座脉冲星的故障可以用来调查的强度，在一个中子星的壳-核耦合，并建议，从故障的恢复是由扭矩所施加的超流组件的核心，从地壳解耦期间的故障。假设再耦合是介导的超流中子和核心的带电组件之间的相互摩擦，我们使用观测到的幅度和时间尺度的最短时标组件的恢复从最近的两个故障在船帆座脉冲星推断的核心部分耦合到地壳在故障期间，因此旋转了故障事件。在故障的双流体动力学模型的框架内，我们分析是否地壳中子单独足以驱动船帆座脉冲星中观察到的故障活动。我们使用两套中子星状态方程（EOSs），这两套状态方程一致地跨越地壳和核，并覆盖在饱和密度$30 < L <120$ MeV的对称能的斜率范围。一组产生最大质量$\approx$ 2.0 $M_{\odot}$，第二组产生最大质量$\approx$ 2.6 $M_{\odot}$。我们还包括了地壳中子夹带的超流晶格的影响。我们发现，对于中硬的地球观测系统，观测结果意味着核心转动惯量的$>70\%$在故障期间耦合到地壳，尽管对于较软的地球观测系统，$L\approx 30$ MeV可以耦合到$5\%$。没有一个状态方程能够单独用地壳中子来重现观测到的毛刺活动，但是将超流涡旋被强烈钉扎到核中的区域扩展到比地壳-核过渡密度高出0.016 fm $^{-3}$的密度，可以恢复与观测到的毛刺活动的一致性。

英文摘要：

We demonstrate that observations of glitches in the Vela pulsar can be used to investigate the strength of the crust-core coupling in a neutron star, and suggest that recovery from the glitch is dominated by torque exerted by the re-coupling of superfluid components of the core that were decoupled from the crust during the glitch. Assuming that the recoupling is mediated by mutual friction between the superfluid neutrons and the charged components of the core, we use the observed magnitudes and timescales of the shortest timescale components of the recoveries from two recent glitches in the Vela pulsar to infer the fraction of the core that is coupled to the crust during the glitch, and hence spun up by the glitch event. Within the framework of a two-fluid hydrodynamic model of glitches, we analyze whether crustal neutrons alone are sufficient to drive the glitch activity observed in the Vela pulsar. We use two sets of neutron star equations of state (EOSs), both of which span crust and core consistently and cover a range of the slope of the symmetry energy at saturation density $30 < L <120$ MeV. One set produces maximum masses $\approx$2.0$M_{\odot}$, the second $\approx$2.6$M_{\odot}$. We also include the effects of entrainment of crustal neutrons by the superfluid lattice. We find that for medium to stiff EOSs, observations imply $>70\%$ of the moment of inertia of the core is coupled to the crust during the glitch, though for softer EOSs $L\approx 30$MeV as little as $5\%$ could be coupled. No EOS is able to reproduce the observed glitch activity with crust neutrons alone, but extending the region where superfluid vortices are strongly pinned into the core by densities as little as 0.016fm$^{-3}$ above the crust-core transition density restores agreement with the observed glitch activity.

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