The Great Dimming of the Hypergiant Star RW Cephei: CHARA Array Images and Spectral Analysis
The Great Dimming of the Hypergiant Star RW Cephei: CHARA Array Images and Spectral Analysis
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DOI：
10.3847/1538-3881/ace59d
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发表时间：
2023-07
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通讯作者：
N. Anugu;F. Baron;D. Gies;C. Lanthermann;G. Schaefer;K. A. Shepard;T. Brummelaar;J. Monnier;S. Kraus;J. L. Bouquin;C. Davies;J. Ennis;T. Gardner;A. Labdon;R. Roettenbacher;B. Setterholm;W. Vollmann;C. Sigismondi
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作者：
N. Anugu;F. Baron;D. Gies;C. Lanthermann;G. Schaefer;K. A. Shepard;T. Brummelaar;J. Monnier;S. Kraus;J. L. Bouquin;C. Davies;J. Ennis;T. Gardner;A. Labdon;R. Roettenbacher;B. Setterholm;W. Vollmann;C. Sigismondi
凉爽的超大恒星RW Cephei目前处于几年前开始的深度光度极小值。这一事件与2019-2020年发生的红色超巨星参宿四大调光有很大的相似之处。我们给出了用查拉阵列干涉仪获得的第一批RW Cephei的分辨率图像。角直径和盖亚距离估计表明，恒星半径为900-1760R⊙，这使RW造父变星成为银河系中已知的最大恒星之一。重建的近红外图像显示出圆盘照明的显著不对称性，有一个明亮的斑块偏离中心，而一个较暗的区域向西移动。成像结果取决于对扩展通量的假设，我们给出了两种不允许扩展发射和不允许扩展发射的情况。我们还提供了RW Cep最近的近红外光谱，它表明在可见光波长下的衰落比在近红外波长下的衰落要大得多，正如预期的被尘埃消光所致。我们认为，恒星变暗是最近的一次表面质量抛射事件的结果，该事件产生了尘埃云，现在部分阻止了恒星光球层。
The cool hypergiant star RW Cephei is currently in a deep photometric minimum that began several years ago. This event bears a strong similarity to the Great Dimming of the red supergiant Betelgeuse that occurred in 2019–2020. We present the first resolved images of RW Cephei that we obtained with the CHARA Array interferometer. The angular diameter and Gaia distance estimates indicate a stellar radius of 900–1760 R ⊙, which makes RW Cephei one of the largest stars known in the Milky Way. The reconstructed, near-infrared images show a striking asymmetry in the disk illumination with a bright patch offset from the center and a darker zone to the west. The imaging results depend on assumptions made about the extended flux, and we present two cases with and without allowing extended emission. We also present a recent near-infrared spectrum of RW Cep that demonstrates that the fading is much larger at visual wavelengths compared to that at near-infrared wavelengths as expected for extinction by dust. We suggest that the star’s dimming is the result of a recent surface mass ejection event that created a dust cloud that now partially blocks the stellar photosphere.