磁化中子星发射线的激射不稳定性理论

在中子星磁轴吸积柱的上部,少数高能电子通过磁镜点反射,可使部份电子的速度分布形成非热分布,由此激发激射(Maser)不稳定性。波被放大,发射出频率近似为电子迴旋频率及其倍频的相干辐射。用此模型计算了HerX-1的迴旋线发射。发现不稳定性增长率与吸积柱中电子数密度成正比,因而比非相干散射产生的连续辐射随电子数密度增长更快;而且发射线的强度和能量均与脉冲相位关联。这个理论可解释近期的HerX-1观测结果。

The Maser Instability Theory on the Emission Line from Magnetic Neutron Star

A nonthermal electron velocity distribution might form in the upper accretion column of magnetic cap of the neutron star. It is caused by that a few of energetic electrons with large pitch angle will reflect at the magnetic mirror point. The electron cyclotron maser instability can be excited by this nonthermal electron distribution, and then the waves, whose frequencies are close to the electron cyclotron frequency and its second harmonic frequency, can be amplified. In the case of emission line from Her X-1, the calculations show that the growth rates of instability increase proportionally with the electron density in the accretion column. Therefore, the variation of line emission luminosity will be faster than the variation of non-coherent continuum emission luminosity when the accretion rate increases. The luminosity and the energy of emission line correlate with the pulse phase of X-ray pulsar as well. Some new observational results from Her X-1 have been interpreted.