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arXiv 1010.4589astro-ph.SR
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来自开普勒数据头四个月的红巨星的星震学:基本参数

Asteroseismology of red giants from the first four months of Kepler data: Fundamental parameters

T. Kallinger, B. Mosser, S. Hekker, D. Huber, D. Stello, S. Mathur, S. Basu, T. R. Bedding, W. J. Chaplin, J. De Ridder, Y. P. Elsworth, S. Frandsen, R. A. Garc… 展开作者

T. Kallinger, B. Mosser, S. Hekker, D. Huber, D. Stello, S. Mathur, S. Basu, T. R. Bedding, W. J. Chaplin, J. De Ridder, Y. P. Elsworth, S. Frandsen, R. A. Garcia, M. Gruberbauer, J. M. Matthews, W. J. Borucki, H. Bruntt, J. Christensen-Dalsgaard, R. L. Gilliland, H. Kjeldsen, D. G. Koch

摘要:

在1000多颗恒星中发现了红巨星太阳型振荡典型频率范围内的明显功率过剩,这是在NASA开普勒卫星科学运行的前138天内观察到的。这个样本包括了质量和半径范围很广的恒星,光谱类型为G和K,亮度从巨星分支的底部一直延伸到高亮度的红巨星。开普勒望远镜的高精度星震观测为检验恒星结构和演化模型以及研究银河系中的恒星星族提供了一个完美的来源。我们将全局模型拟合到所观察到的频谱,这使我们能够准确地估计颗粒背景信号和全局振荡参数,例如最大振荡功率的频率。我们发现径向和非径向振荡模式的规律,并使用一种新的技术来自动识别模式的程度和相同的球形度的连续模式之间的特征频率分离。在大多数情况下,我们也可以测量小的分离。地震参数用于估计恒星的质量和半径,并通过使用覆盖广泛参数范围的恒星模型的广泛网格将恒星放置在H-R图中。在整个分析过程中使用贝叶斯技术使我们能够确定所有参数的可靠不确定性。我们提供了大量红巨星样本的精确地震参数及其不确定性,并确定了它们的星震基本参数。我们研究了恒星的金属丰度对它们在H-R图中位置的影响。我们研究了红巨星种群的红团和凸块,并将它们与合成人口进行比较,发现了质量和金属丰度梯度的红团和明确的证据,二次丛人口。

英文摘要:

Clear power excess in a frequency range typical for solar-type oscillations in red giants has been detected in more than 1000 stars, which have been observed during the first 138 days of the science operation of the NASA Kepler satellite. This sample includes stars in a wide mass and radius range with spectral types G and K, extending in luminosity from the bottom of the giant branch up to high-luminous red giants. The high-precision asteroseismic observations with Kepler provide a perfect source for testing stellar structure and evolutionary models, as well as investigating the stellar population in our Galaxy. We fit a global model to the observed frequency spectra, which allows us to accurately estimate the granulation background signal and the global oscillation parameters, such as the frequency of maximum oscillation power. We find regular patterns of radial and non-radial oscillation modes and use a new technique to automatically identify the mode degree and the characteristic frequency separations between consecutive modes of the same spherical degree. In most cases, we can also measure the small separation. The seismic parameters are used to estimate stellar masses and radii and to place the stars in an H-R diagram by using an extensive grid of stellar models that covers a wide parameter range. Using Bayesian techniques throughout our analysis allows us to determine reliable uncertainties for all parameters. We provide accurate seismic parameters and their uncertainties for a large sample of red giants and determine their asteroseismic fundamental parameters. We investigate the influence of the stars' metallicities on their positions in the H-R diagram. We study the red-giant populations in the red clump and bump and compare them to a synthetic population and find a mass and metallicity gradient in the red clump and clear evidence of a secondary-clump population.

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