arXiv 0712.08472007-12astro-ph

晕白矮星双星对LISA信号的贡献

The Contribution of Halo White Dwarf Binaries to the LISA Signal

Ashley J. Ruiter, Krzysztof Belczynski, Matthew Benacquista, Kelly Holley-Bockelmann

备注：: 8 pages, 3 figures, ApJ submitted

摘要：

银河系的双白矮星被假定为未来空间引力波观测站LISA的混淆有限噪声源。直到最近，银河系的人口包括一个相对较好的研究磁盘人口，一个有点研究较小的隆起人口和一个大部分未知的，但潜在的大晕人口。有人认为，晕人口可能会产生一个信号，这是强得多（因子~5的频谱振幅）比磁盘人口。然而，这个令人惊讶的结果并不是基于对晕白矮星种群的实际计算，而是基于（i）人们可以从盘种群的特性推断晕种群特性的假设和（ii）假设（不现实地）晕中大量的白矮星。我们进行了第一次计算的晕白矮星人口使用人口合成模型。我们与银河系盘+核球中的双白矮星产生的信号的比较清楚地表明，双白矮星晕信号不可能超过银河系其余部分的信号。使用微透镜结果给出晕中白矮星含量的上限（白矮星中~ 30%重子质量），我们预测的晕信号比盘+凸起信号低10倍。即使在所有重子晕质量都在白矮星中发现的难以置信的情况下，晕信号也不会变得与盘+凸起的信号相比较，因此对其他LISA源的检测仍然具有可以忽略的影响。

英文摘要：

Galactic double white dwarfs were postulated as a source of confusion limited noise for LISA, the future space-based gravitational wave observatory. Until very recently, the Galactic population consisted of a relatively well studied disk population, a somewhat studied smaller bulge population and a mostly unknown, but potentially large halo population. It has been argued that the halo population may produce a signal that is much stronger (factor of ~5 in spectral amplitude) than the disk population. However, this surprising result was not based on an actual calculation of a halo white dwarf population but was derived on (i) the assumption that one can extrapolate the halo population properties from those of the disk population and (ii) the postulated (unrealistically) high number of white dwarfs in the halo. We perform the first calculation of a halo white dwarf population using population synthesis models. Our comparison with the signal arising from double white dwarfs in the Galactic disk+bulge clearly shows that it is impossible for the double white dwarf halo signal to exceed that of the rest of the Galaxy. Using microlensing results to give an upper limit on the content of white dwarfs in the halo (~30 % baryonic mass in white dwarfs), our predicted halo signal is a factor of 10 lower than the disk+bulge signal. Even in the implausible case where all of the baryonic halo mass is found in white dwarfs, the halo signal does not become comparable to that of the disk+bulge, and thus would still have a negligible effect on the detection of other LISA sources.

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