Light-curve inversions with truncated least-squares principal components: Tests and application to HD 291095 = V1355 Orionis
Light-curve inversions with truncated least-squares principal components: Tests and application to HD 291095 = V1355 Orionis
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DOI：
10.1002/asna.200710963
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发表时间：
2008-04
影响因子：
0.9
通讯作者：
I. Savanov;K. Strassmeier
中科院分区：
文献类型：
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作者：
I. Savanov;K. Strassmeier
我们提出了一种新的反演代码，从旋转恒星的光曲线重建恒星表面的光斑结构。我们的代码采用了一种方法，该方法使用了反问题对象主成分的截短最小二乘估计。我们使用斑点填充因子作为未知对象。表示快速旋转的K子巨人的各种测试用例用于前向问题。然后执行测试以恢复人工输入映射，包括数据错误和输入参数错误。我们证明了该解决方案对诸如光球温度、光斑温度、重力、倾角、未斑点亮度和不同光斑分布等虚假输入参数的鲁棒性，并且我们还证明了该解决方案对光斑纬度的不敏感性。在整个恒星表面散布斑点或有相位间隙的测试不会产生虚假的有效经度。然后将该代码应用于斑点亚巨星HD291095 10年来的V波段和I波段光曲线数据。总共给出了22条光曲线。我们发现，在大多数时间里，它的斑点集中在平均间隔180°的两个活跃经度周围。这两个经度的主要活动区可能每3.15±0.23年发生一次转换，而亮度的幅度调制可能发生在3.0±0.15年。第一次，我们发现了证据表明，活动翻转的时间与最小光和最小光度振幅的时间一致，即最大斑点。通过与同步多普勒图像的比较，我们得出结论，活动翻转可能发生在恒星的旋转极附近。（©2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim）
We present a new inversion code that reconstructs the stellar surface spot configuration from the light curve of a rotating star. Our code employs a method that uses the truncated least-squares estimation of the inverse problem's objects principal components. We use spot filling factors as the unknown objects. Various test cases that represent a rapidly-rotating K subgiant are used for the forward problem. Tests are then performed to recover the artificial input map and include data errors and input-parameter errors. We demonstrate the robustness of the solution to false input parameters like photospheric temperature, spot temperature, gravity, inclination, unspotted brightness and different spot distributions and we also demonstrate the insensitivity of the solution to spot latitude. Tests with spots peppered over the entire stellar surface or with phase gaps do not produce fake active longitudes. The code is then applied to ten years of V and I -band light curve data of the spotted sub-giant HD291095. A total of 22 light curves is presented. We find that for most of the time its spots were grouped around two active longitudes separated on average by 180°. Switches of the dominant active region between these two longitudes likely occurred about every 3.15±0.23 years while the amplitude modulation of the brightness occurred with a possible period of 3.0±0.15 years. For the first time, we found evidence that the times of the activity flips coincide with times of minimum light as well as minimum photometric amplitude, i.e. maximum spottedness. From a comparison with simultaneous Doppler images we conclude that the activity flips likely take place near the rotational pole of the star. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)