参宿四在H波段的斑点状表面成像
Imaging the spotty surface of Betelgeuse in the H band
摘要：
本文报道了在三望远镜干涉仪IOTA上对参宿四进行的H波段干涉观测。我们对参宿四及其不对称性进行成像，以了解光球的空间变化，包括其直径，边缘变暗，有效温度，周围亮度和亮（或暗）星斑。我们使用不同的光球和尘埃环境的理论模拟模型的能见度数据。我们用参数化建模和两种图像重建算法：MIRA和WISARD制作图像。我们用线性和二次模型测量平均肢体变暗直径为44.28 +/- 0.15 mas，用MARCS模型测量Rosseland直径为45.03 +/- 0.12 mas。这些测量结果使我们得出更新的有效温度为3600 +/- 66 K。我们检测到一个完全解决的环境，硅酸盐尘埃壳可能作出贡献。通过两种成像重建算法，我们揭示了参宿四表面的两个亮点。一个光斑的直径约为11质量，约占总通量的8.5%。第二个是未分辨的（直径< 9质量），占总通量的4.5%。参宿四在H波段的解析图像在百分之几的水平上是不对称的。在此波长范围内未检测到MOLsphere。测得的肢体变暗的量与模型预测吻合得很好。在恒星表面成像的两个斑点是对流细胞的潜在特征。
英文摘要：
This paper reports on H-band interferometric observations of Betelgeuse made at the three-telescope interferometer IOTA. We image Betelgeuse and its asymmetries to understand the spatial variation of the photosphere, including its diameter, limb darkening, effective temperature, surrounding brightness, and bright (or dark) star spots. We used different theoretical simulations of the photosphere and dusty environment to model the visibility data. We made images with parametric modeling and two image reconstruction algorithms: MIRA and WISARD. We measure an average limb-darkened diameter of 44.28 +/- 0.15 mas with linear and quadratic models and a Rosseland diameter of 45.03 +/- 0.12 mas with a MARCS model. These measurements lead us to derive an updated effective temperature of 3600 +/- 66 K. We detect a fully-resolved environment to which the silicate dust shell is likely to contribute. By using two imaging reconstruction algorithms, we unveiled two bright spots on the surface of Betelgeuse. One spot has a diameter of about 11 mas and accounts for about 8.5% of the total flux. The second one is unresolved (diameter < 9 mas) with 4.5% of the total flux. Resolved images of Betelgeuse in the H band are asymmetric at the level of a few percent. The MOLsphere is not detected in this wavelength range. The amount of measured limb-darkening is in good agreement with model predictions. The two spots imaged at the surface of the star are potential signatures of convective cells.
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