Magnetospheric return-current-heated atmospheres of rotation-powered millisecond pulsars
Magnetospheric return-current-heated atmospheres of rotation-powered millisecond pulsars
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DOI：
10.1051/0004-6361/202037824
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发表时间：
2020-02
影响因子：
6.5
通讯作者：
Tuomo Salmi;V. Suleimanov;J. Nattila;J. Poutanen
中科院分区：
文献类型：
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作者：
Tuomo Salmi;V. Suleimanov;J. Nattila;J. Poutanen
我们计算了精确的大气模型的旋转动力毫秒双星中，一个中子星星（NS）的极冠外部加热的磁层返回电流。外部冲压压力，能量损失，和穿透带电粒子的停止深度计算自洽与大气模型，而不是假设一个简化的深加热的大气辐射平衡。我们使用精确的康普顿散射形式主义模型的出射X射线辐射的属性。深度加热近似被发现只有当大部分的热来自于洛伦兹因子为γ <$100的超相对论性粒子轰击时才有效。在相反的制度，大气达到一个独特的两层结构与过热的光学薄的皮肤上的光学厚冷等离子体。过热的皮肤强烈地改变了出射辐射：它在光谱中产生了康普顿上散射的高能尾，并改变了辐射光束模式，从边缘变暗到边缘变亮，以发射硬X射线。发射特性的这种剧烈变化可能会对推断的NS脉冲轮廓参数产生重大影响，例如，由中子星星内部成分探索者执行的参数。最后，返回电流粒子的能量分布和大气发射特性之间的联系提供了一个新的工具，探索脉冲星磁层的精确物理。
We computed accurate atmosphere models of rotation-powered millisecond pulsars in which the polar caps of a neutron star (NS) are externally heated by magnetospheric return currents. The external ram pressure, energy losses, and stopping depth of the penetrating charged particles were computed self-consistently with the atmosphere model, instead of assuming a simplified deep-heated atmosphere in radiative equilibrium. We used exact Compton scattering formalism to model the properties of the emergent X-ray radiation. The deep-heating approximation was found to be valid only if most of the heat originates from ultra-relativistic bombarding particles with Lorentz factors ofγ ≳ 100. In the opposite regime, the atmosphere attains a distinct two-layer structure with an overheated optically thin skin on top of an optically thick cool plasma. The overheated skin strongly modifies the emergent radiation: It produces a Compton-upscattered high-energy tail in the spectrum and alters the radiation beaming pattern from limb darkening to limb brightening for emitted hard X-rays. This kind of drastic change in the emission properties can have a significant impact on the inferred NS pulse profile parameters as performed, for example, by Neutron star Interior Composition ExploreR. Finally, the connection between the energy distribution of the return current particles and the atmosphere emission properties offers a new tool to probe the exact physics of pulsar magnetospheres.