Radiation from rapidly rotating oblate neutron stars
Radiation from rapidly rotating oblate neutron stars
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快速旋转的扁中子星的辐射
DOI：
10.1051/0004-6361/201630261
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发表时间：
2017
影响因子：
6.5
通讯作者：
P. Pihajoki
中科院分区：
文献类型：
--
作者：
J. Nattila;P. Pihajoki
本文详细介绍了快速旋转扁球形致密天体辐射的理论框架。使用哈密顿-雅可比形式主义，我们表明，特殊的相对论旋转效应，如像差的角度，多普勒增压，和时间膨胀自然出现从旋转的紧凑对象的广义相对论治疗。我们使用的Butterfly-Ipser度量扩展到第二阶旋转，因此包括光弯曲，帧拖动，和四极偏差对我们的测地线计算的影响。我们还详细描述了所使用的数值算法，并提供了一个名为BENDER的数值框架的开源实现。作为应用，我们研究光谱线轮廓（即，涂抹内核）从快速旋转的扁圆中子星。我们发现，在这个度量描述中，二阶四极效应不足以产生狭窄的可观察到的功能，在光谱能量分布几乎任何物理上现实的参数组合，因此，实际上检测到它们是不可能的。还针对所有视角报告了旋转拖尾核的十分之一最大值处的全宽和半最大值处的全宽。然后，这些可以被用来定量地估计旋转拖尾对所观察到的光谱的影响。我们还计算了准确的脉冲轮廓和观测者的天空图的快速旋转吸积毫秒恒星上的热点发射。这使我们能够量化人们期望从典型的快速旋转的毫秒脉冲星上观察到的脉冲部分的强度。
A theoretical framework for emission originating from rapidly rotating oblate compact objects is described in detail. Using a Hamilton-Jacobi formalism, we show that special relativistic rotational effects such as aberration of angles, Doppler boosting, and time dilatation naturally emerge from the general relativistic treatment of rotating compact objects. We use the Butterworth–Ipser metric expanded up to the second order in rotation and hence include effects of light bending, frame-dragging, and quadrupole deviations on our geodesic calculations. We also give detailed descriptions of the numerical algorithms used and provide an open-source implementation of the numerical framework called BENDER. As an application, we study spectral line profiles (i.e., smearing kernels) from rapidly rotating oblate neutron stars. We find that in this metric description, the second-order quadrupole effects are not strong enough to produce narrow observable features in the spectral energy distribution for almost any physically realistic parameter combination, and hence, actually detecting them is unlikely. The full width at tenth-maximum and full width at half-maximum of the rotation smearing kernels are also reported for all viewing angles. These can then be used to quantitatively estimate the effects of rotational smearing on the observed spectra. We also calculate accurate pulse profiles and observer skymaps of emission from hot spots on rapidly rotating accreting millisecond pulsars. These allow us to quantify the strength of the pulse fractions one expects to observe from typical fast-spinning millisecond pulsars.