论文标题
快速旋转中子星的观察出现：X射线突发，冷却尾巴方法和半径测定
Observational appearance of rapidly rotating neutron stars: X-ray bursts, cooling tail method, and radius determination
论文作者
论文摘要
低质量X射线二进制中的中子星（NSS）以足够高的频率旋转以显着偏离球形（$ν_* \ sim $ 200--600 Hz）。我们研究了快速旋转对NS观测外观的影响。我们建议使用准确的完全相对论的计算，将快速旋转的NS的重力质量和赤道半径与质量$ M $和质量$ m $和半径$ r $相关的分析公式与质量$ m $和半径$ r $。我们使用修改后的schwarzschild（MOS）近似在不同的倾斜角度观察到的旋转ns的光谱，其中在schwarzschild指标中计算了光弯曲，但是在光子送出的schwarzschild指标中，在schwarzschild trage traging和trage拖动和四杆矩中近似计算。我们将冷却尾巴方法推广到迅速旋转的NS的情况下，以获得具有相同重型质量质量的相应非旋转ns的最可能的$ m $和$ r $。我们使用先前计算的NS大气模型通过稀释的黑体从NS表面近似局部光谱。我们表明，如果使用非旋转ns的冷却尾巴方法，则可以将NS半径高估为3--3.5公里，$ r \ $ r \约11 $ km，以$ν_* = $ 700 Hz旋转。我们将该方法应用于从$ν_* \ $ 532 Hz中观察到的X射线爆发，sax J1810.8 $ - $ 2609。如果在倾斜度i = 60 ver i = 60 ver和$ r = 11.2 \ pm0.5 $ km的面对面视图的情况下，则无旋转NS的结果（假设$ m = 1.5 m = 1.5 m_ \ odot $）将变为$ 11.8 \ pm0.5 $ km，比使用标准的冷却型旋转的旋转方法更小，而$ r = 11.2 \ pm0.5 $ km。这些迅速旋转的NS的相应赤道半径为12.3 $ \ pm 0.6 $ km（对于i = 60 ver）和11.6 $ \ pm 0.6 $ \，km，km（对于i = 0 deg）。
Neutron stars (NSs) in low-mass X-ray binaries rotate at frequencies high enough to significantly deviate from sphericity ($ν_* \sim$ 200--600 Hz). We investigate the effects of rapid rotation on the observational appearance of a NS. We propose analytical formulae relating gravitational mass and equatorial radius of the rapidly rotating NS to the mass $M$ and radius $R$ of a non-rotating NS of the same baryonic mass using accurate fully relativistic computations. We compute spectra from an oblate rotating NS observed at different inclination angles using the modified oblate Schwarzschild (MOS) approximation, where light bending is computed in Schwarzschild metric, but frame dragging and quadrupole moment of a NS are approximately accounted for in the photon redshift calculations. We generalize the cooling tail method to the case of a rapidly rotating NS to obtain the most probable values of $M$ and $R$ of the corresponding non-rotating NS with the same baryonic mass. We approximate the local spectra from the NS surface by a diluted blackbody using previously computed NS atmosphere models. We show that the NS radius could be overestimated by 3--3.5 km for face-on stars of $R\approx 11$ km rotating at $ν_* =$ 700 Hz if the version of the cooling tail method for a non-rotating NS is used. We apply the method to an X-ray burst observed from the NS rotating at $ν_* \approx$ 532 Hz in SAX J1810.8$-$2609. The resulting radius of the non-rotating NS (assuming $M=1.5 M_\odot$) becomes $11.8\pm0.5$ km if it is viewed at inclination i=60 deg and $R=11.2\pm0.5$ km for a face-on view, which are smaller by 0.6 and 1.2 km than the radius obtained using standard cooling tail method ignoring rotation. The corresponding equatorial radii of these rapidly rotating NSs are 12.3$\pm 0.6$ km (for i=60 deg) and 11.6$\pm 0.6$\,km (for i=0 deg).
