A Bayesian approach to the modelling of α Cen A
A Bayesian approach to the modelling of α Cen A
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DOI：
10.1111/j.1365-2966.2012.21818.x
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发表时间：
2012-12-01
影响因子：
4.8
通讯作者：
Christensen-Dalsgaard, J.
中科院分区：
文献类型：
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作者：
Bazot, M.;Bourguignon, S.;Christensen-Dalsgaard, J.
确定恒星的物理特性是一个反问题，包括估计恒星结构和演化模型的参数，以及知道某些可观测的量。我们使用贝叶斯方法来解决Cen a的这个问题，它允许我们结合要估计的参数的先验信息，以便更好地约束问题。我们的策略是基于使用马尔可夫链蒙特卡罗（MCMC）算法来估计恒星参数的后验概率密度：质量，年龄，初始化学成分等。我们使用恒星演化代码astec来模拟恒星。为了约束该模型，同时考虑了地震和非地震观测。在astec中使用两个自由参数或五个自由参数，测试了几种不同的策略来拟合这些值。因此，我们能够证明，当参数数量增加时，MCMC方法相对于更经典的基于网格的策略变得有效。通过对后验概率密度的统计分析，我们的MCMC算法的结果使我们能够得出恒星参数和鲁棒不确定性的估计。我们还能够计算半人马座a中存在对流核心的几率。当使用对核心敏感的地震观测约束时，这些几率可以上升到类似于40%以上。将结果与以前的研究进行比较也表明，这些地震约束对我们了解这颗恒星的结构至关重要。
Determining the physical characteristics of a star is an inverse problem consisting of estimating the parameters of models for the stellar structure and evolution, and knowing certain observable quantities. We use a Bayesian approach to solve this problem for a Cen A, which allows us to incorporate prior information on the parameters to be estimated, in order to better constrain the problem. Our strategy is based on the use of a Markov chain Monte Carlo (MCMC) algorithm to estimate the posterior probability densities of the stellar parameters: mass, age, initial chemical composition, etc. We use the stellar evolutionary code astec to model the star. To constrain this model both seismic and non-seismic observations were considered. Several different strategies were tested to fit these values, using either two free parameters or five free parameters in astec. We are thus able to show evidence that MCMC methods become efficient with respect to more classical grid-based strategies when the number of parameters increases. The results of our MCMC algorithm allow us to derive estimates for the stellar parameters and robust uncertainties thanks to the statistical analysis of the posterior probability densities. We are also able to compute odds for the presence of a convective core in a Cen A. When using core-sensitive seismic observational constraints, these can rise above similar to 40 per cent. The comparison of results to previous studies also indicates that these seismic constraints are of critical importance for our knowledge of the structure of this star.