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arXiv 1202.1265astro-ph.EP
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半人马座阿尔法星B周围宜居带的振荡

Oscillations in the Habitable Zone around Alpha Centauri B

Duncan Forgan

摘要:

半人马座阿尔法AB系统是一个有吸引力的径向速度观测,以检测潜在的系外行星。半人马座阿尔法星A和B的高金属丰度表明,它们可能拥有能够形成行星的星周盘。作为距离太阳最近的恒星系统,有超过一个世纪的精确天体测量(半人马座阿尔法B表现出低色球活动),可以用相对便宜的仪器对半人马座阿尔法B潜在的系外行星系统进行高精度的测量。研究该系统可居住性的作者通常采用基于全球辐射平衡模型的宜居带(HZ),该模型忽略了半人马座阿尔法A的辐射扰动。我们使用一维纬向能量平衡模型(LEBMs),充分纳入半人马座阿尔法星A的存在作为天文强迫类地行星气候的一种手段,研究了半人马座阿尔法星B周围行星的可居住性。我们发现,HZ的程度是相对不变的半人马座阿尔法A的存在下,但有变化的分数可居住性的行星轨道在边界的区域由于半人马座阿尔法A,即使在零偏心率的情况下。在所有行星轨道上都可以观察到几K的温度振荡,其强度随行星的海洋比例和倾角而变化。

英文摘要:

The Alpha Centauri AB system is an attractive one for radial velocity observations to detect potential exoplanets. The high metallicity of both Alpha Centauri A and B suggest that they could have possessed circumstellar discs capable of forming planets. As the closest star system to the Sun, with well over a century of accurate astrometric measurements (and Alpha Centauri B exhibiting low chromospheric activity) high precision surveys of Alpha Centauri B's potential exoplanetary system are possible with relatively cheap instrumentation. Authors studying habitability in this system typically adopt habitable zones (HZs) based on global radiative balance models that neglect the radiative perturbations of Alpha Centauri A. We investigate the habitability of planets around Alpha Centauri B using 1D latitudinal energy balance models (LEBMs), which fully incorporate the presence of Alpha Centauri A as a means of astronomically forcing terrestrial planet climates. We find that the extent of the HZ is relatively unchanged by the presence of Alpha Centauri A, but there are variations in fractional habitability for planets orbiting at the boundaries of the zone due to Alpha Centauri A, even in the case of zero eccentricity. Temperature oscillations of a few K can be observed at all planetary orbits, the strength of which varies with the planet's ocean fraction and obliquity.

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