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arXiv 1504.05029astro-ph.HE
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过渡毫秒脉冲星PSR J1023 +0038亚亮盘态的螺旋桨模型

A propeller model for the sub-luminous disk state of the transitional millisecond pulsar PSR J1023+0038

A. Papitto, D. F. Torres

摘要:

最近发现的毫秒射电星在由其磁场旋转或物质吸积提供动力的状态之间切换,证明了毫秒射电星和低质量X射线双星中的中子星之间的紧密联系。过渡毫秒双星也表现出一种神秘的中间状态,在这种状态下,中子星被一个吸积盘包围,它发出相干的X射线脉动,但相对于吸积的中子星,它在X射线中是亚发光的,在伽马射线中比旋转动力状态下的毫秒双星更亮。在这里,我们模拟的X射线和伽马射线发射观察到PSR J1023+0038在这样一个状态的基础上的假设,即大部分的磁盘流入被推离快速旋转的中子星磁层,电子可以被加速到几个GeV的能量在湍流磁盘磁层边界。我们表明,同步和自同步康普顿发射来自这样一个区域,连同硬盘发射典型的低状态的吸积紧凑的对象,是能够解释在X射线和伽马射线波段观察到的辐射。PSR J1023+0038观测到的平均发射是由速率为$(1-3)\times10^{-11} M_{\odot}/yr$的盘内流模拟的,在半径30至45公里范围内截断,与推进磁层的假设一致。我们比较了我们获得的结果与模型,而假设旋转动力脉冲星是打开的,显示如何在类似的情况下释放的自旋下降功率是很难解释观测到的发射的幅度。

英文摘要:

The discovery of millisecond pulsars switching between states powered either by the rotation of their magnetic field or by the accretion of matter, has recently proved the tight link shared by millisecond radio pulsars and neutron stars in low-mass X-ray binaries. Transitional millisecond pulsars also show an enigmatic intermediate state in which the neutron star is surrounded by an accretion disk, it emits coherent X-ray pulsations, but is sub-luminous in X-rays with respect to accreting neutron stars, and is brighter in gamma-rays than millisecond pulsars in the rotation-powered state. Here, we model the X-ray and gamma-ray emission observed from PSR J1023+0038 in such a state based on the assumption that most of the disk in-flow is propelled away by the rapidly rotating neutron star magnetosphere, and that electrons can be accelerated to energies of a few GeV at the turbulent disk-magnetosphere boundary. We show that the synchrotron and self-synchrotron Compton emission coming from such a region, together with the hard disk emission typical of low states of accreting compact objects, is able to explain the radiation observed in the X-ray and gamma-ray band. The average emission observed from PSR J1023+0038 is modelled by a disk in-flow with a rate of $(1-3)\times10^{-11} M_{\odot}/yr$, truncated at a radius ranging between 30 and 45 km, compatible with the hypothesis of a propelling magnetosphere. We compare the results we obtained with models that rather assume that a rotation-powered pulsar is turned on, showing how the spin down power released in similar scenarios is hardly able to account for the magnitude of the observed emission.

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