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arXiv 0909.0506astro-ph.SR
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从星震资料确定恒星半径

Determination of stellar radii from asteroseismic Data

Sarbani Basu, William J. Chaplin, Yvonne Elsworth

摘要:

NASA开普勒任务旨在通过凌日寻找行星。准确和精确的被探测行星的半径取决于准确地知道主星的半径,这是困难的,除非恒星的温度和光度是精确的。然而,开普勒有一个星震学计划,它将提供地震变量,可以轻松,准确和极其精确地测量恒星半径。本文介绍了用地震变量和常规变量组合确定恒星半径的Yale-Birmingham(YB)方法,并分析了这些变量对结果的影响。我们发现,对于主序星,视差的知识是不重要的,以获得准确的半径使用YB方法:我们可以得到结果的准确性和精度优于百分之几,如果我们知道这些恒星的有效温度和地震参数。金属性也没有多大区别。然而,对有效温度和金属丰度以及地震参数的良好估计对于正确确定次巨星的半径至关重要。另一方面,对于红巨星,我们发现,如果没有对视差的良好估计,就不可能正确地确定半径。我们发现,所谓的“表面项”在地震数据的推断半径的影响很小。在某些情况下,对流混合长度的不确定性可能很重要,并可能导致推断半径的系统性变化。用模拟数据进行盲测,以匹配开普勒星震勘测阶段的预期数据,结果表明,使用我们的方法可以成功地推断恒星半径。

英文摘要:

The NASA Kepler mission is designed to find planets through transits. Accurate and precise radii of the detected planets depend on knowing the radius of the host star accurately, which is difficult unless the temperature and luminosity of the star are known precisely. Kepler, however, has an asteroseismology programme that will provide seismic variables that can characterise stellar radii easily, accurately, and extremely precisely. In this paper we describe the Yale-Birmingham (YB) method to determine stellar radii using a combination of seismic and conventional variables, and analyse the effect of these variables on the result. We find that for main-sequence stars, a knowledge of the parallax is not important to get accurate radii using the YB method: we can get results to an accuracy and precision of better than a few percent if we know the effective temperature and the seismic parameters for these stars. Metallicity does not make much difference either. However, good estimates of the effective temperature and metallicity, along with those of the seismic parameters, are essential to determine radii of sub giants properly. On the other hand, for red giants we find that determining radii properly is not possible without a good estimate of the parallax. We find that the so called "surface term" in the seismic data has minimal effect on the inferred radii. Uncertainties in the convective mixing length can matter under some circumstances and can cause a systematic shift in the inferred radii. Blind tests with data simulated to match those expected from the asteroseismic Survey Phase of Kepler show that it will be possible to infer stellar radii successfully using our method.

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