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arXiv 1608.01375astro-ph.HE
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孤立脉冲星的制动指数II:一个新的脉冲星磁性双偶极模型

Braking Index of Isolated Pulsars II: A novel two-dipole model of pulsar magnetism

Oliver Q. Hamil, Nick J. Stone, Jirina R. Stone

摘要:

磁偶极辐射(MDR)模型是目前解释脉冲星辐射的最好方法。然而,观测到的辐射的最特征的参数,制动指数n $_{\rm obs}$显示偏差的所有八个最好的研究孤立的恒星,从简单的模型预测n $_{\rm dip}$ = 3。该指数取决于旋转频率及其一阶和二阶时间导数,但也取决于磁偶极矩和倾角以及脉冲星的转动惯量在时间上恒定的假设。在最近的一篇论文[Phys. Rev. D 91,063007(2015)]中,我们得出结论,转动惯量仅随频率变化不能解释观察到的制动指数。最近Lyne等人提出了蟹状星云脉冲星的磁偶极矩以每100年0.6 $^{\circ}$/$\dotα$/$\sim$/$^{\circ}$/100年的速率从自转轴向外迁移的可能观测证据。本文探讨了具有恒定转动惯量和磁偶极矩但倾角可变$α$的MDR模型。我们首先讨论的影响的变化$α$上观察到的制动指数,并显示他们都可以理解。但是,未提供$α$变化的原因解释。在讨论了磁源后,我们提出了一个简单的机制,在$α$的变化的基础上的玩具模型,其中磁结构在磁源的磁结构由两个相互作用的偶极子。我们表明,这样的系统可以解释螃蟹的观察和测量的制动指数。

英文摘要:

The magnetic dipole radiation (MDR) model is currently the best approach we have to explain pulsar radiation. However a most characteristic parameter of the observed radiation, the braking index n$_{\rm obs}$ shows deviations for all the eight best studied isolated pulsars, from the simple model prediction n$_{\rm dip}$ = 3. The index depends upon the rotational frequency and its first and second time derivatives, but also on the assumption of that the magnetic dipole moment and inclination angle, and the moment of inertia of the pulsar are constant in time. In a recent paper [Phys. Rev. D 91, 063007 (2015)] we showed conclusively that changes in the moment of inertia with frequency alone, cannot explain the observed braking indices. Possible observational evidence for the magnetic dipole moment migrating away from the rotational axis at a rate $\dotα$ $\sim$ 0.6$^{\circ}$ per 100 years over the life time of the Crab pulsar has been recently suggested by Lyne et al. In this paper, we explore the MDR model with constant moment of inertia and magnetic dipole moment but variable inclination angle $α$. We first discuss the effect of the variation of $α$ on the observed braking indices and show they all can be understood. However, no explanation for the origin of the change in $α$ is provided. After discussion of the possible source(s) of magnetism in pulsars we propose a simple mechanism for the change in $α$ based on a toy model in which the magnetic structure in pulsars consists of two interacting dipoles. We show that such a system can explain the Crab observation and the measured braking indices.

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。

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