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arXiv 1203.0891astro-ph.HE
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毫秒吸积中子星中r模产生的强磁场:诱导形变和引力波发射

Generation of strong magnetic fields by r-modes in millisecond accreting neutron stars: induced deformations and gravitational wave emission

Carmine Cuofano, Simone Dall'Osso, Alessandro Drago, Luigi Stella

摘要:

由r-模不稳定性引起的微分旋转可以在吸积的毫秒自旋中子星的核中产生非常强的环形场。我们在r模的演化方程中明确地引入磁阻尼项,并在牛顿极限下数值求解,以跟踪内部磁场的发展和增长。我们发现,后者的强度可以达到大的值,$B \sim 10^{14} $ G,在最快的吸积中子星的核心。这是强大到足以诱导一个显着的四极矩的中子星质量分布,对应于一个椭圆率$|ε_B}| \sim 10^{-8}$。如果感应磁场的对称轴与自旋轴不对齐,中子星就会辐射出引力波。我们认为这一机制可以解释在低质量X射线双星中吸积中子星中观测到的自旋频率上限。我们讨论的相关性,我们的研究结果的搜索引力波。

英文摘要:

Differential rotation induced by the r-mode instability can generate very strong toroidal fields in the core of accreting, millisecond spinning neutron stars. We introduce explicitly the magnetic damping term in the evolution equations of the r-modes and solve them numerically in the Newtonian limit, to follow the development and growth of the internal magnetic field. We show that the strength of the latter can reach large values, $B \sim 10^{14} $ G, in the core of the fastest accreting neutron stars. This is strong enough to induce a significant quadrupole moment of the neutron star mass distribution, corresponding to an ellipticity $|ε_B}| \sim 10^{-8}$. If the symmetry axis of the induced magnetic field is not aligned with the spin axis, the neutron star radiates gravitational waves. We suggest that this mechanism may explain the upper limit of the spin frequencies observed in accreting neutron stars in Low Mass X-Ray Binaries. We discuss the relevance of our results for the search of gravitational waves.

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