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arXiv 0906.5002astro-ph.SR
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在CoRoT系外行星场中观测到的红巨星类太阳振荡的特征

Characteristics of solar-like oscillations in red giants observed in the CoRoT exoplanet field

S. Hekker, T. Kallinger, F. Baudin, J. De Ridder, C. Barban, F. Carrier, A. P. Hatzes, W. W. Weiss, A. Baglin

摘要:

在第一个长期运行(~150天)期间,在CoRoT的系外行星领域的观测增加了G-K巨星的数量,这些巨星被观测到类似太阳的振荡,增加了100倍。这为从统计意义上研究它们的振荡特征提供了可能性。我们的目标是了解红巨星中最大振荡功率(nu_max)频率的统计分布,并寻找nu_max和大分离(delta_nu)之间可能的相关性。nu_max分布在20 - 40 microHz之间显示出明显的峰值。对于大约一半的恒星,我们用至少两种方法获得delta_nu。nu_max和delta_nu之间的相关性遵循与类太阳恒星相同的标度关系。nu_max分布的形状可以部分地用低频的颗粒化和高频的白噪声来解释,但观察到的恒星的种群密度也是一个重要因素。从红巨星的delta_nu和nu_max之间的相关性遵循与类太阳恒星相同的标度关系这一事实,我们得出结论,在大气压力标度高度上的声音旅行时间与整个恒星的声音旅行时间成比例,而不管演化如何。

英文摘要:

Observations during the first long run (~150 days) in the exo-planet field of CoRoT increase the number of G-K giant stars for which solar-like oscillations are observed by a factor of 100. This opens the possibility to study the characteristics of their oscillations in a statistical sense. We aim to understand the statistical distribution of the frequencies of maximum oscillation power (nu_max) in red giants and to search for a possible correlation between nu_max and the large separation (delta_nu). The nu_max distribution shows a pronounced peak between 20 - 40 microHz. For about half of the stars we obtain delta_nu with at least two methods. The correlation between nu_max and delta_nu follows the same scaling relation as inferred for solar-like stars. The shape of the nu_max distribution can partly be explained by granulation at low frequencies and by white noise at high frequencies, but the population density of the observed stars turns out to be also an important factor. From the fact that the correlation between delta_nu and nu_max for red giants follows the same scaling relation as obtained for sun-like stars, we conclude that the sound travel time over the pressure scale height of the atmosphere scales with the sound travel time through the whole star irrespective of evolution.

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