新生NS的倾斜角分布：内粘度和磁场的作用
The distribution of tilt angles in newly born NSs: role of interior viscosity and magnetic field
摘要：
研究了中子星物质的粘性对年轻中子星自旋轴和磁轴倾角分布的影响。假设NS形状是由磁致变形决定的，并且内部磁场的环向分量超过极向分量，我们证明了由体粘滞引起的进动运动的耗散可以自然地产生一个双模倾斜角分布，正如在射电/ $γ$射线天体中观察到的那样，如果内部B场为$\sim (10^{11} - 10^{15})$ ~G且出生自旋周期为$\sim 10 - 300$ ~ ms，则实现$χ\sim (20^\circ - 70^\circ)$的概率较低。作为该模型的推论，NS形状仅由极向磁场确定的想法，或由地壳离心变形引起的，与年轻恒星的倾角分布不一致。当应用到蟹状星云脉冲星，与$χ\sim 45^\circ - 70^\circ$和出生自旋$\sim$ 20毫秒，我们的模型意味着：（i）磁致椭圆率是$ε_B \gtrsim 3 \times 10^{-6}$ ;（ii）测得的正$\dotχ \sim 3.6 \times 10^{-12}$ rad s $^{-1}$需要一个额外的粘性过程，作用于一个时间尺度$\lesssim 10^4$ yrs. We解释为壳核耦合通过相互摩擦在超流NS内部。我们的模型的一个关键含义是GW信号在（两倍）的NS的自旋频率，由于$ε_B \sim 10^{-6}$。这可以通过先进的LIGO/Virgo在设计灵敏度下运行来检测。
英文摘要：
We study how the viscosity of neutron star (NS) matter affects the distribution of tilt angles ($χ$) between the spin and magnetic axes in young pulsars. Under the hypothesis that the NS shape is determined by the magnetically-induced deformation, and that the toroidal component of the internal magnetic field exceeds the poloidal one, we show that the dissipation of precessional motions by bulk viscosity can naturally produce a bi-modal distribution of tilt angles, as observed in radio/$γ$-ray pulsars, with a low probability of achieving $χ\sim (20^\circ - 70^\circ)$ if the interior B-field is $\sim (10^{11} - 10^{15})$~G and the birth spin period is $\sim 10 - 300$~ms. As a corollary of the model, the idea that the NS shape is solely determined by the poloidal magnetic field, or by the centrifugal deformation of the crust, is found to be inconsistent with the tilt angle distribution in young pulsars. When applied to the Crab pulsar, with $χ\sim 45^\circ - 70^\circ$ and birth spin $\sim$ 20 ms, our model implies that: (i) the magnetically-induced ellipticity is $ε_B \gtrsim 3 \times 10^{-6}$; (ii) the measured positive $\dotχ \sim 3.6 \times 10^{-12}$ rad s$^{-1}$ requires an additional viscous process, acting on a timescale $\lesssim 10^4$ yrs. We interpret the latter as crust-core coupling via mutual friction in the superfluid NS interior. One critical implication of our model is a GW signal at (twice) the spin frequency of the NS, due to $ε_B \sim 10^{-6}$. This could be detectable by Advanced LIGO/Virgo operating at design sensitivity.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
