X射线脉冲星高吸积柱的脉冲轮廓
Pulse profiles of tall accretion columns in X-ray pulsars
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中文总结 AI 辅助
本文通过射线追踪计算超临界吸积柱的辐射，提出通用无量纲参数描述脉冲非对称性，模型可重现X射线脉冲星的非对称脉冲轮廓，适用于最亮天体。
中文摘要 AI 辅助
吸积X射线脉冲星（XRPs）是强磁化中子星（NSs），其特征是与磁层旋转相关的周期性变化模式（脉冲）。许多此类天体展现出复杂的非对称脉冲轮廓，难以用现有模型框架解释。我们计算了超临界吸积状态下磁化中子星的X射线辐射脉冲，此时辐射激波远高于中子星表面，观测到的辐射来自激波下游的两个光学厚吸积柱。我们表明，基于第一性原理计算的吸积柱束流模式具有重现XRP脉冲形状多样性的潜力。假设柱表面以黑体形式局部辐射，其温度分布遵循Basko和Sunyaev（1976）的解法。采用的场几何为倾斜偶极子。考虑到激波上方的两股吸积流会衰减并散射吸积柱的辐射。利用射线追踪技术，我们获得了由质量吸积率、磁倾角、观测者方向以及决定被吸积物质加载的特定磁场线组的参数所控制的各种脉冲形状。我们提出了一个通用的无量纲参数，用于定量描述脉冲的非对称性。该模型自然产生了在许多XRP中观测到的非对称脉冲轮廓。然而，其适用性仅限于最明亮的天体，如脉冲超亮X射线源和银河系XRP的强耀斑。
英文摘要
Accreting X-ray pulsars (XRPs) are strongly magnetized neutron stars (NSs) distinguished by a periodic variability pattern related to the rotation of their magnetospheres (pulsations). Many of these objects show complex asymmetric pulse profiles that are difficult to explain in the framework of existing models. We calculate the pulsations of X-ray radiation from a magnetized NS in the regime of supercritical accretion, when the radiation shock wave is high above the NS surface, and the observed radiation comes from two optically thick accretion columns located downstream of the shocks. We show that the accretion column beam pattern calculated from the first principles has a potential of reproducing the variety of XRP pulse shapes. The surfaces of the columns are assumed to radiate locally as blackbodies with the temperature distribution following the solution of Basko and Sunyaev (1976). The adopted geometry of the field is an inclined dipole. It is taken into account that the two accretion flows above the shocks attenuate and scatter the radiation of the accretion columns. Using the ray-tracing technique, we obtain a vast variety of pulse shapes controlled by the mass accretion rate, magnetic angle, the direction towards the observer, and the parameters that determine the particular set of magnetic field lines being loaded with accreting matter. We propose a universal dimensionless parameter describing the asymmetry of a pulse quantitatively. The model naturally produces asymmetric pulse profiles observed in many XRPs. Its applicability, however, is limited to the brightest objects like pulsating ultraluminous Xray sources and strong flares of Galactic XRPs.
发表机构
- Moscow State University（莫斯科国立大学）
- The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University（特拉维夫大学雷蒙德和贝弗利·萨克勒物理与天文学学院）
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