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arXiv 1406.0874astro-ph.HE
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表面温度不均匀引起的孤立中子星的光谱特征

Spectral features in isolated neutron stars induced by inhomogeneous surface temperatures

Daniele Viganò, Rosalba Perna, Nanda Rea, José A. Pons

摘要:

几个孤立的中子星的热X射线谱显示出与纯黑体的偏离。这些光谱特征的精确物理解释对我们理解大气成分、磁场强度和拓扑结构以及致密物质状态方程具有深远的意义。具体细节因源而异,对这些特征的常见解释包括磁化大气或凝聚表面中的原子跃迁,以及表面附近热电离层中产生的回旋加速器线。在这里,我们定量评估的X射线光谱畸变引起的不均匀的温度分布的中子星表面。为了这个目的,我们探讨了几个表面温度分布,我们模拟其相应的广义相对论X射线光谱(假设各向同性,黑体发射),并适合后者与一个单一的黑体模型。我们发现,在某些情况下,一个虚假的“谱线”的存在下,需要在一个高的显着性水平,以获得统计上可接受的拟合,与中心能量和等效宽度类似的值通常观察到的。我们还对一个特定的物体RX J0806.4-4123进行了拟合,找到了几个能够模拟观察到的光谱的表面温度分布。探索的效果不太可能在所有检测到线的源中起作用,但在某些情况下,它确实可能是导致这些线出现的原因。我们的研究结果加强了这样的想法,即表面温度各向异性可以是一个重要的因素,应该考虑和探索,也结合更复杂的排放模型,如大气。

英文摘要:

The thermal X-ray spectra of several isolated neutron stars display deviations from a pure blackbody. The accurate physical interpretation of these spectral features bears profound implications for our understanding of the atmospheric composition, magnetic field strength and topology, and equation of state of dense matter. With specific details varying from source to source, common explanations for the features have ranged from atomic transitions in the magnetized atmospheres or condensed surface, to cyclotron lines generated in a hot ionized layer near the surface. Here we quantitatively evaluate the X-ray spectral distortions induced by inhomogeneous temperature distributions of the neutron star surface. To this aim, we explore several surface temperature distributions, we simulate their corresponding general relativistic X-ray spectra (assuming an isotropic, blackbody emission), and fit the latter with a single blackbody model. We find that, in some cases, the presence of a spurious 'spectral line' is required at a high significance level in order to obtain statistically acceptable fits, with central energy and equivalent width similar to the values typically observed. We also perform a fit to a specific object, RX J0806.4-4123, finding several surface temperature distributions able to model the observed spectrum. The explored effect is unlikely to work in all sources with detected lines, but in some cases it can indeed be responsible for the appearance of such lines. Our results enforce the idea that surface temperature anisotropy can be an important factor that should be considered and explored also in combination with more sophisticated emission models like atmospheres.

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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