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arXiv 1504.01715gr-qcastro-ph.IM
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系外行星的随机引力波背景

Stochastic Gravitational Wave Background from Exoplanets

Anirban Ain, Shilpa Kastha, Sanjit Mitra

摘要:

最近的系外行星调查预测,我们的银河系中有非常大的行星系统,平均每颗恒星有一颗以上的行星,总数可能约为2000亿颗。这些以电磁观测为基础的调查仅限于太阳系的一个非常小的邻域,估计仅依赖于对几千颗行星的观测。另一方面,行星围绕恒星的轨道运动预计会发出引力波(GW),这可以提供电磁天文学无法获得的行星信息。行星的累积效应,周期从几小时到几年不等,预计会产生一个随机GW背景(SGWB)。我们计算特征GW应变的基础上观察到的行星参数分布的背景。我们还表明,在不同的频率,整合的河外背景是可比或小于银河系背景。我们的估计表明,净背景是显着低于拟议的GW实验在不同频段的灵敏度。然而,我们注意到,频谱的峰值,在$10^{-5}$ Hz附近,并不太远低于拟议的天基GW任务。未来的太空任务可能能够观察或严格限制这种信号,这可能是探测整个星系系外行星群的唯一方法。

英文摘要:

Recent exoplanet surveys have predicted a very large population of planetary systems in our galaxy, more than one planet per star on the average, perhaps totalling about two hundred billion. These surveys, based on electro-magnetic observations, are limited to a very small neighbourhood of the solar system and the estimations rely on the observations of only a few thousand planets. On the other hand, orbital motions of planets around stars are expected to emit gravitational waves (GW), which could provide information about the planets not accessible to electro-magnetic astronomy. The cumulative effect of the planets, with periods ranging from few hours to several years, is expected to create a stochastic GW background (SGWB). We compute the characteristic GW strain of this background based on the observed distribution of planet parameters. We also show that the integrated extragalactic background is comparable or less than the galactic background at different frequencies. Our estimate shows that the net background is significantly below the sensitivities of the proposed GW experiments in different frequency bands. However, we notice that the peak of the spectrum, at around $10^{-5}$Hz, is not too far below the proposed space based GW missions. A future space based mission may be able to observe or tightly constrain this signal, which will possibly be the only way to probe the galactic population of exoplanets as a whole.

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