CHANDRA PHASE-RESOLVED X-RAY SPECTROSCOPY OF THE CRAB PULSAR
CHANDRA PHASE-RESOLVED X-RAY SPECTROSCOPY OF THE CRAB PULSAR
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DOI：
10.1088/0004-637x/743/2/139
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发表时间：
2004-02
期刊：
影响因子：
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通讯作者：
M. Weisskopf;A. Tennant;D. Yakovlev;A. Harding;V. Zavlin;S. O’Dell;R. Elsner;W. Becker
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作者：
M. Weisskopf;A. Tennant;D. Yakovlev;A. Harding;V. Zavlin;S. O’Dell;R. Elsner;W. Becker
我们提出了一项关于蟹状脉冲星 X 射线光谱特性的新研究。钱德拉 X 射线天文台卓越的角分辨率能够将脉冲星与周围的星云区分开来。将光谱作为脉冲相位的函数进行分析，可以对星际 X 射线消光进行最小偏差的测量，这主要是由于光电吸收，其次是由于蟹状星云方向的尘埃颗粒的散射。我们修改了之前的发现，即螃蟹的视线中氧气不足，并提供了更高精确度和更少偏差的测量结果。使用 Wilms 等人的丰度和横截面。我们发现 [O/H] = (5.28 ± 0.28) × 10−4 （4.9 × 10−4 是太阳丰度）。我们还首次测量了星际颗粒从图像中散射通量的影响。我们发现 τscat = 0.147 ± 0.043。作为脉冲相位函数的光谱分析也可以测量 X 射线光谱指数，即使在脉冲最小值时也是如此，尽管统计不确定性不断增加。光谱变化总体上与正弦变化一致。正弦曲线的唯一显着变化发生在与光学偏振幅度和位置角中一些相当突然的行为相同的相位范围内。我们还将这些光谱变化与在伽马射线中观察到的光谱变化进行比较，并得出结论，我们的测量既是一个挑战，也是未来建模的指南，因此最终将帮助我们理解脉冲星磁层中的对级联过程。这些数据还用于为不同的中子星大气模型设定新的、偏差较小的中子星表面温度上限。我们讨论如何将这些数据与中子星冷却和中子星内部的理论模型最好地联系起来。这些数据限制了脉冲星核心的中微子发射率和热覆盖层中的轻元素数量。这些观测结果使得脉冲星，无论其包层的成分如何，其中微子发射率比通过修改的乌尔卡过程冷却的非超流体恒星的标准率高出~0.2。观察结果还表明该速率较低，但现在包络中的吸积物质数量有限。
We present a new study of the X-ray spectral properties of the Crab Pulsar. The superb angular resolution of the Chandra X-Ray Observatory enables distinguishing the pulsar from the surrounding nebulosity. Analysis of the spectrum as a function of pulse phase allows the least-biased measure of interstellar X-ray extinction due primarily to photoelectric absorption and secondarily to scattering by dust grains in the direction of the Crab Nebula. We modify previous findings that the line of sight to the Crab is underabundant in oxygen and provide measurements with improved accuracy and less bias. Using the abundances and cross sections from Wilms et al. we find [O/H] = (5.28 ± 0.28) × 10−4 (4.9 × 10−4 is solar abundance). We also measure for the first time the impact of scattering of flux out of the image by interstellar grains. We find τscat = 0.147 ± 0.043. Analysis of the spectrum as a function of pulse phase also measures the X-ray spectral index even at pulse minimum—albeit with increasing statistical uncertainty. The spectral variations are, by and large, consistent with a sinusoidal variation. The only significant variation from the sinusoid occurs over the same phase range as some rather abrupt behavior in the optical polarization magnitude and position angle. We also compare these spectral variations to those observed in gamma-rays and conclude that our measurements are both a challenge and a guide to future modeling and will thus eventually help us understand pair cascade processes in pulsar magnetospheres. The data are also used to set new, and less biased, upper limits to the surface temperature of the neutron star for different models of the neutron star atmosphere. We discuss how such data are best connected to theoretical models of neutron star cooling and neutron star interiors. The data restrict the neutrino emission rate in the pulsar core and the amount of light elements in the heat-blanketing envelope. The observations allow the pulsar, irrespective of the composition of its envelope, to have a neutrino emission rate higher than ∼0.2 of the standard rate of a non-superfluid star cooling via the modified Urca process. The observations also allow the rate to be lower but now with a limited amount of accreted matter in the envelope.