Mode identification in rapidly rotating stars
Mode identification in rapidly rotating stars
复制标题
快速旋转恒星的模式识别
DOI：
10.1051/0004-6361/200911914
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发表时间：
2009
影响因子：
6.5
通讯作者：
Reese D
中科院分区：
文献类型：
--
作者：
Reese D
背景最近对快速旋转多方模型和基于自洽场方法的模型中脉动模态的计算表明，只要底层旋转剖面不太微分，低度脉动模态的频谱可以用类似于塔苏尔渐近公式的经验公式来描述。目的考虑到这个渐近公式的简单性，我们研究它是否可以提供一种识别快速旋转恒星中脉动模态的方法。方法我们开发了一种新的方法模式识别方案包括扫描多维参数空间以获取产生最佳拟合渐近谱的公式系数。然后，在基于渐近公式的人工频谱、随机频率以及基于预先已知模式识别的全数值本征模式计算的频谱上测试该模式识别方案。我们还研究了添加随机频率来模拟混沌模式的影响，这些混沌模式也预计会出现在此类恒星中。结果在没有混沌模式的情况下，只要这些频率足够接近其渐近值，就可以准确地找到大多数观测到的频率的正确模式识别。添加随机频率很快就会出现问题并阻碍正确的模式识别。修改模式识别方案以拒绝最差的拟合模式可以带来一些改进，但结果仍然比没有混沌模式的情况差。
ContextRecent calculations of pulsation modes in rapidly rotating polytropic models and models based on the Self-Consistent Field method have shown that the frequency spectrum of low degree pulsation modes can be described by an empirical formula similar to Tassoul's asymptotic formula, provided that the underlying rotation profile is not too differential.AimsGiven the simplicity of this asymptotic formula, we investigate whether it can provide a means by which to identify pulsation modes in rapidly rotating stars.MethodsWe develop a new mode identification scheme which consists in scanning a multidimensional parameter space for the formula coefficients which yield the best-fitting asymptotic spectra. This mode identification scheme is then tested on artificial spectra based on the asymptotic formula, on random frequencies and on spectra based on full numerical eigenmode calculations for which the mode identification is known beforehand. We also investigate the effects of adding random frequencies to mimic the effects of chaotic modes which are also expected to show up in such stars.ResultsIn the absence of chaotic modes, it is possible to accurately find a correct mode identification for most of the observed frequencies provided these frequencies are sufficiently close to their asymptotic values. The addition of random frequencies can very quickly become problematic and hinder correct mode identification. Modifying the mode identification scheme to reject the worst fitting modes can bring some improvement but the results still remain poorer than in the case without chaotic modes.