The Evolving Radio Photospheres of Long-period Variable Stars
The Evolving Radio Photospheres of Long-period Variable Stars
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长周期变星演化的射电光球层
DOI：
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发表时间：
2018
影响因子：
5.3
通讯作者：
Kazunori Akiyama
中科院分区：
文献类型：
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作者：
L. D. Matthews;M. J. Reid;K. Menten;Kazunori Akiyama;Kazunori Akiyama
卡尔·G·詹斯基甚大阵列在46 GHz(λ≈7毫米)的观测被用来测量四颗长周期变星的射电光球的大小和形状：R狮子座(R Leo)，IRC+10216(CW狮子座)，χ天鹅座(χCyg)和W长蛇座(W Hya)。恒星的形状从近圆形到椭圆形不等，∼为0.15。与几年前的观测相比，每一颗恒星的光球参数(平均直径、形状和/或通量密度)都随着时间的推移而变化。在可见域和使用稀疏建模图像重建技术获得的图像中，也可以看到射电表面上亮度不对称和不均匀的证据。这些趋势可以解释为恒星表面大规模不规则对流的表现，尽管不能排除非径向脉动的影响。我们的数据还允许对IRC+10216的自行进行新的评估。我们的测量结果与之前从射电波长测量得到的值是一致的，我们没有发现来自双星伙伴的统计上显著的天体测量扰动的证据。
Observations with the Karl G. Jansky Very Large Array at 46 GHz (λ ≈ 7 mm) have been used to measure the size and shape of the radio photospheres of four long-period variable stars: R Leonis (R Leo), IRC+10216 (CW Leonis), χ Cygni (χ Cyg), and W Hydrae (W Hya). The shapes of the stars range from nearly round to ellipticities of ∼0.15. Comparisons with observations taken several years earlier show that the photospheric parameters (mean diameter, shape, and/or flux density) of each of the stars have changed over time. Evidence for brightness asymmetries and nonuniformities across the radio surfaces is also seen in the visibility domain and in images obtained using a sparse-modeling image reconstruction technique. These trends may be explained as manifestations of large-scale irregular convective flows on the stellar surface, although effects from nonradial pulsations cannot be excluded. Our data also allow a new evaluation of the proper motion of IRC+10216. Our measurement is in agreement with previous values obtained from radio-wavelength measurements, and we find no evidence of statistically significant astrometric perturbations from a binary companion.