arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2602.02733astro-ph.HE
收藏

亚临界X射线脉冲星中的回旋谱线:蒙特卡洛模拟揭示观测变异的起源

Cyclotron lines in subcritical X-ray pulsars: Monte Carlo simulations reveal the origin of the observed variability

University of Crete(克里特大学);Institute of Astrophysics, Foundation for Research and Technology-Hellas(希腊研究与技术基金会天体物理研究所);Princeton University(普林斯顿大学);Max-Planck-Institut für extraterrestrische Physik(马克斯·普朗克地外物理研究所);Ludwig-Maximilians Universität(慕尼黑路德维希-马克西米利安大学)

Prodromos Fotiadis, Nick Loudas, Nikolaos D. Kylafis, Joachim Trümper

AI总结:

通过蒙特卡洛辐射传输模拟,研究亚临界光度X射线脉冲星中回旋共振散射特征(CRSF)的变异,发现中心能量和线宽与光度正相关,且依赖于视角。

摘要:

观测到的X射线脉冲星(XRPs)中的回旋共振散射特征(CRSFs)表现出强烈的变异性。在亚临界光度范围内,中心能量($E_{CRSF}$)和线宽($σ_{CRSF}$)通常与X射线光度呈正相关。我们定量研究了观测变异性的物理起源,重点关注吸积漏斗中等离子体流引起的共振散射和多普勒频移效应。我们开发了一个相对论性蒙特卡洛代码,在热点上方的吸积漏斗中进行详细的辐射传输计算,并推导出角度相关谱。采用解析的等离子体密度和速度分布来考虑辐射压力对流动的影响,并使用了近似的共振散射截面。我们改变吸积光度以探索CRSF特性的相应变异性。出射谱呈现出一个显著的不对称CRSF,伴随一个宽的蓝翼。CRSF相对于经典回旋能量系统性地红移,红移量在高光度和较大视角$θ$时减小。对于所有视角,$E_{CRSF}$和$σ_{CRSF}$都与光度正相关。然而,它们的绝对值强烈依赖于视角,表明在脉冲周期内存在显著变异性,并对系统几何敏感。在固定光度下,$E_{CRSF}$($σ_{CRSF}$)随$\cosθ$增加而减小(增加)。因此,预期相位分辨观测将揭示CRSF中心能量与宽度之间的反相关。当应用于XRP GX 304$-$1时,该模型在吸积漏斗主要被侧向观测的几何条件下,重现了在近一个数量级光度范围内观测到的CRSF变异性。

英文摘要:

Observed cyclotron resonant scattering features (CRSFs) in X-ray pulsars (XRPs) exhibit strong variability. In the subcritical luminosity regime, the centroid energy ($E_{CRSF}$) and line width ($σ_{CRSF}$) often show positive correlations with the X-ray luminosity. We investigate the physical origin of the observed variability quantitatively, focusing on the effects of resonant scattering and Doppler shift induced by the plasma flow in the accretion funnel. We developed a relativistic Monte Carlo code to perform detailed radiative transfer calculations in the accretion funnel above the hotspot and derive angle-dependent spectra. Analytical plasma density and velocity profiles were adopted to account for the effects of radiation pressure on the flow. Approximate resonant scattering cross-sections were employed. We varied the accretion luminosity to explore the resulting variability of the CRSF properties. The emergent spectra exhibit a prominent, asymmetric CRSF accompanied by a broad blue wing. The CRSF is systematically redshifted relative to the classical cyclotron energy, with the magnitude of the redshift decreasing at higher luminosities and for larger viewing angles $θ$. Both $E_{CRSF}$ and $σ_{CRSF}$ correlate positively with luminosity for all viewing angles. Their absolute values, however, depend strongly on the viewing angle, indicating substantial variability over the pulse cycle and sensitivity to the system geometry. At fixed luminosity, $E_{CRSF}$ ($σ_{CRSF}$) decreases (increases) with increasing $\cosθ$. Consequently, phase-resolved observations are expected to reveal an anticorrelation between the CRSF centroid energy and width. When applied to the XRP GX 304$-$1, the model reproduces the observed CRSF variability over nearly an order of magnitude in luminosity for geometries in which the accretion funnel is predominantly viewed edge-on.

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。

↑