蟹状星云脉冲星的精确自行和年轻中子星自旋-反冲排列检验的困难
A Precise Proper Motion for the Crab Pulsar, and the Difficulty of Testing Spin-Kick Alignment for Young Neutron Stars
摘要：
我们提出了一个详细的测量蟹状星云脉冲星自行，其主要目标是比较其自行的方向与投影轴的脉冲星风星云（投影旋转轴的脉冲星）。我们证明，我们的测量是强大的，只有+/-0.4 mas/yr的每个组件的自行的不确定性。相对于脉冲星的静止标准，我们发现μ_alpha = -11.7+/-0.4+/-0.5 mas/yr，μ_delta = +4.2+/-0.4+/-0.5 mas/yr，这两个不确定度分别来自于测量和修正自行参考系的修正。将这种自行与脉冲星风星云的对称轴相比较，我们还必须考虑脉冲星的祖先的未知速度（假设约为10 km/s），因此为自行的每个分量增加+/-2 mas/yr的额外不确定性，尽管这可能会更大。这意味着预计与星云轴的偏差为14+/-2+/-9度。我们的结论是，比较中子星的运动方向，以一个固定的轴的个别测量的精度往往会受到有关参考系和祖属性的基本不确定性。自旋踢（mis-alignment）的问题，以及它对超新星核心坍缩过程中的不对称性和其他过程的影响，最好通过考虑这些测量的统计集合来解决，而不是对单个源的详细研究。[删节]
英文摘要：
We present a detailed measurement of the proper motion of the Crab pulsar, with the primary goal of comparing the direction of its proper motion with the projected axis of its pulsar wind nebula (the projected spin axis of the pulsar). We demonstrate that our measurement is robust and has an uncertainty of only +/-0.4 mas/yr on each component of the proper motion. We find mu_alpha = -11.7+/-0.4+/-0.5 mas/yr and mu_delta = +4.2+/-0.4+/-0.5 mas/yr relative to the pulsar's standard of rest, where the two uncertainties are from the measurement and the ncertainties in correcting the proper motion reference frame, respectively. Comparing this proper motion to the symmetry axis of the pulsar wind nebula, we must also consider the unknown velocity of the pulsar's progenitor (assumed to be ~10 km/s), and hence add an additional uncertainty of +/-2 mas/yr to each component of the proper motion, although this could be significantly larger. This implies a projected misalignment with the nebular axis of 14+/-2+/-9 degrees. We conclude that the precision of individual measurements which compare the direction of motion of a neutron star to a fixed axis will often be limited by fundamental uncertainties regarding reference frames and progenitor properties. The question of spin-kick (mis)alignment, and its implications for asymmetries and other processes during supernova core-collapse, is best approached by considering a statistical ensemble of such measurements, rather than detailed studies of individual sources. [abriged]
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