Puppis A中PSR J0821-4300表面X射线发射和观察几何的模拟
Modeling the Surface X-ray Emission and Viewing Geometry of PSR J0821-4300 in Puppis A
摘要：
我们发现，一对热，对极的热点上的中子星表面是能够充分占脉冲星的双黑体光谱和能量依赖的脉冲轮廓，包括观察到的180度相位反转在约1.2千电子伏。通过比较所观察到的脉冲调制和相位的模型预测，我们强烈约束热点极（xi）和视线（psi）相对于自旋轴的角度。对于标称半径R = 12 km和距离D = 2.2 kpc，我们发现（xi，psi）=（86 d，6 d），1-sigma误差椭圆为（2d，1d）;该解在两个角度退化。这种几何形状的最佳拟合光谱模型要求两个发射点的温度相差2倍，其面积相差约20倍。包括发射强度的余弦波束图案修改结果，将角度减小到（84 d，3d）;然而，该模型在统计上与各向同性发射情况没有区别。我们还提出了Pdot < 3.5E-16（2-sigma）的周期导数的新上限，将全球偶极子磁场限制在B_s <2.0E 11 G，证实PSR J 0821 -4300是一颗“反磁星”。“我们讨论的背景下，观察和理论的非均匀表面温度孤立NS的弱和强磁场。要解释PSR J 0821 -4300的不均匀温度，可能需要一个比外部全球偶极子场强得多的地壳场。
英文摘要：
We show that a pair of thermal, antipodal hot-spots on the neutron star surface is able to fully account for the pulsar's double blackbody spectrum and energy-dependent pulse profile, including the observed 180 degree phase reversal at approximately 1.2 keV. By comparing the observed pulse modulation and phase to the model predictions, we strongly constrain the hot-spot pole (xi) and the line-of-sight (psi) angles with respect to the spin axis. For a nominal radius of R = 12 km and distance D = 2.2 kpc, we find (xi,psi) = (86d,6d), with 1-sigma error ellipse of (2d,1d); this solution is degenerate in the two angles. The best-fit spectral model for this geometry requires that the temperatures of the two emission spots differ by a factor of 2 and their areas by a factor of ~ 20. Including a cosine-beamed pattern for the emitted intensity modifies the result, decreasing the angles to (84d,3d); however this model is not statistically distinguishable from the isotropic emission case. We also present a new upper limit on the period derivative of Pdot < 3.5E-16 (2-sigma), which limits the global dipole magnetic field to B_s < 2.0E11 G, confirming PSR J0821-4300 as an "anti-magnetar." We discuss the results in the context of observations and theories of nonuniform surface temperature on isolated NSs of both weak and strong magnetic field. To explain the nonuniform temperature of PSR J0821-4300 may require a crustal field that is much stronger than the external, global dipole field.
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