Asteroseismic model fitting by comparing ? n l values
Asteroseismic model fitting by comparing ? n l values
复制标题
通过比较进行星震模型拟合？
DOI：
10.1051/0004-6361/201526593
复制
发表时间：
2015
影响因子：
6.5
通讯作者：
Roxburgh I
中科院分区：
文献类型：
--
作者：
Roxburgh I
我们提出了一种基于比较模型和观测值的星震模型拟合算法，该值由ϵℓ(ν[n+ϵℓ(ν/2+ℓ)][n+ℓ/2+ϵℓ(νnℓ]定义，其中Δ是平均大间隔。我们证明，如果两个恒星模型具有相同的内部结构但不同的外层，则它们的ϵℓ(ν值之间的差值，内插到相同的频率，仅塌缩为频率的函数，而与角度数ℓ无关。该算法通过比较模型值和观测值在减去最佳拟合与频率独立函数(ϵℓℱ(ν)后的差值来测试良好拟合，并且只需要对模型值而不是观测值进行内插，因此观测值上的误差是不相关的；它与分配给频率径向排序的值无关，并且不需要计算模型的内部相移。我们将其与提出的直接频率匹配技术进行对比，该技术在减去对这些差异的ℓ独立拟合后，将观测频率和模型频率之间的差异降至最小。我们证明了这种技术在原理上是有缺陷的，所有具有相同无量纲结构但任何质量和半径的模型都具有与观测数据集相同的拟合质量，并且它可能给出错误的最佳拟合模型。我们通过比较恒星模型来说明epsilon匹配技术，然后将其应用于HD 177153(又名PERKY)上的数据。通过与一组主要序列演化模型的比较，我们发现，满足光度、半径、Δ和ϵ匹配约束的模型，质量在1.155±0.035M⊙，年龄在4.486±0.250×109yr。由于大的分离和半径依赖于表层，我们检验了“纯表层无关”的模型拟合，模型拟合的唯一约束是光度和epsilon匹配，结果表明最佳的模型是：EM/M⊙=1.13±0.06，年龄=4.62±0.39×10~9yr。
We present an asteroseismic model fitting algorithm based on comparing model and observedϵℓ(ν) values defined in terms of frequencies byνnℓ= Δ [n+ℓ/ 2 +ϵℓ(νnℓ) ] where Δ is an average large separation. We show that if two stellar models have the same interior structure but different outer layers then the difference between theirϵℓ(ν) values, interpolated to the same frequencies, collapses to a function only of frequency, independent of angular degreeℓ. The algorithm tests the goodness fit by comparing the difference in model and observedϵvalues after having subtracted off a best fitℓindependent function of frequency ℱ(ν), and only requires interpolation in model values and not in observed values so the errors on the observed values are uncorrelated; it is independent of thenvalues assigned to the radial ordering of the frequencies and does not require the calculation of inner phase shifts of the model. We contrast this to a proposed direct frequency matching technique which minimises the difference between observed and model frequencies after having subtracted off anℓindependent fit to these differences. We show this technique is flawed in principle, that all models with the same dimensionless structure but any mass and radius have the same quality of fit to an observed data set, and that it can give erroneous best fit models. We illustrate the epsilon matching technique by comparing stellar models and then apply it to data on HD 177153 (aka Perky). On comparing observations with a set of main sequence evolutionary models we find that models which satisfy constraints on the luminosity, radius, Δ, and onϵmatching, have masses in the range 1.155 ± 0.035M⊙and ages in the range 4.486 ± 0.250 × 109yr. Since the large separation and the radius are surface layer dependent we examine “pure surface layer independent” model fitting where the only constraints on the model fitting are on the luminosity and epsilon matching, and show that the best fit models haveM/M⊙= 1.13 ± 0.06 and age = 4.62 ± 0.39 × 109yr.