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941.
942.
M. Van Der Klis 《Astrophysics and Space Science》2005,300(1-3):149-157
There are remarkable similarities between the rapid X-ray variability of low-magnetic field neutron stars in low mass X-ray
binaries, and that of black holes. In particular at frequencies < 100 Hz, their power spectra can be strikingly similar. The
highest frequency phenomena (kilohertz QPOs, black hole high-frequency QPOs and neutron star hectohertz QPOs) are the ones
that show most differences, perhaps because they originate closest to the compact object. Most variability components vary
in frequency in correlation with one another, and the correlations once again are very similar across neutron stars and black
holes – some extend even to white dwarfs. Although this does not strictly require that all phenomena whose frequencies are
involved are caused by the same physics in all three source types, this does indicate that basic properties of the accretion
flow which are the same in all three source types play an important role in generating at least some of the frequencies. 相似文献
943.
Michelle B. Larson † Bennett Link 《Monthly notices of the Royal Astronomical Society》2002,333(3):613-622
Many radio pulsars exhibit glitches wherein the star's spin rate increases fractionally by ∼10−10 –10−6 . Glitches are ascribed to variable coupling between the neutron star crust and its superfluid interior. With the aim of distinguishing among different theoretical explanations for the glitch phenomenon, we study the response of a neutron star to two types of perturbations to the vortex array that exists in the superfluid interior: (1) thermal motion of vortices pinned to inner crust nuclei, initiated by sudden heating of the crust, (e.g., a starquake), and (2) mechanical motion of vortices (e.g., from crust cracking by superfluid stresses). Both mechanisms produce acceptable fits to glitch observations in four pulsars, with the exception of the 1989 glitch in the Crab pulsar, which is best fitted by the thermal excitation model. The two models make different predictions for the generation of internal heat and subsequent enhancement of surface emission. The mechanical glitch model predicts a negligible temperature increase. For a pure and highly conductive crust, the thermal glitch model predicts a surface temperature increase of as much as ∼2 per cent, occurring several weeks after the glitch. If the thermal conductivity of the crust is lowered by a high concentration of impurities, however, the surface temperature increases by ∼10 per cent about a decade after a thermal glitch. A thermal glitch in an impure crust is consistent with the surface emission limits following the 2000 January glitch in the Vela pulsar. Future surface emission measurements coordinated with radio observations will constrain glitch mechanisms and the conductivity of the crust. 相似文献
944.
A. Treves S. Campana M. Chieregato A. Moretti T. Nelson M. Orio 《Astrophysics and Space Science》2007,308(1-4):167-169
Blank field sources (BFS) are good candidates for hosting dim isolated neutron stars (DINS). The results of a search of BFS
in the ROSAT HRI images are revised. We then focus on transient BFS, arguing that they belong to a rather large population.
The perspectives of future research on DINS are then discussed.
相似文献
945.
本文导出了磁偏轴椭球在坍缩时磁轴的变化公式。计算结果表明,磁轴和自转轴重合的情况在坍缩时是不稳定的,稍有偏离,磁轴与自转轴间的夹角就要增大。这有助于说明脉冲星磁轴与自转轴偏离的原因以及通常在研究中假定两者相互垂直的合理性。 相似文献
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本文采用相对论微扰法处理Fe(+24)系统,利用解析形式的波函数计算其低能态的能级结构及Kα、Kβ特征线(作为对比,我们也计算了Fe(+25)系统).通过与现有的Fe(+25)Kα线的实验和理论比较,证明我们的方法是准确可信的,而在数学计算上则更加简便。利用这一结果,对小质量X射线密近双星的Fe(+24)K特征线进行了简要的定性分析. 相似文献