论文标题
炸鸡蛋星云的光学/近红外观察：从巨大的黄色超巨人的100年时间范围内的多个壳弹出
Optical/near-infrared observations of the Fried Egg Nebula: Multiple shell ejections on a 100 yr timescale from a massive yellow hypergiant
论文作者
论文摘要
语境。在其进化的最新阶段，巨大恒星的命运高度取决于其质量损失率/几何形状，因此知道靠近恒星及其周围环境的偶色的几何形状至关重要。目标。我们旨在研究质量损失发作的性质（即几何，速率）。在这种情况下，黄色超巨人是伟大的目标。方法。我们在光谱和光度法（X-Shooter/VLT），SpectroPolopOlopimetric（ISIS/WHT）和干涉重力 - amber/vlti）中分析了大量的光学/近红外数据，朝着黄色的Hypergiant IRAS 17163-3907。我们在这些波长下在毫米级尺度上介绍了IRA 17163-3907的第一个独立于模型的重建图像。最后，我们采用2D辐射转移模型，以同时采用修订后的GAIA距离（DR2），以同时拟合DEDDENDED的光度法和已发表的Visir图像的径向分布。结果。大约2μM的干涉测量值表明，BRγ发射比NA I和连续发射更扩展和不对称。除了围绕IRAS 17163-3907的两个已知壳外，我们还报告了第三个热内壳的存在，最大动力学年龄仅为30年。结论。与BRγ相比，与恒星距离近距离的Na I发射的存在的解释是各种研究的挑战。我们认为，不需要假局层的存在，而是光学深度效应。这三个观察到的独特的质量损失发作的特征是不同的质量损失率，并且可以为质量损失机制提供理论，这是一个仍在争论中的话题。我们在光电脉动和风稳定性机制的背景下讨论这些。
Context. The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss rate/geometry and therefore knowing the geometry of the circumstellar material close to the star and its surroundings is crucial. Aims. We aim to study the nature (i.e. geometry, rates) of mass-loss episodes. In this context, yellow hypergiants are great targets. Methods. We analyse a large set of optical/near-infrared data, in spectroscopic and photometric (X-shooter/VLT), spectropolarimetric (ISIS/WHT), and interferometric GRAVITY-AMBER/VLTI) modes, toward the yellow hypergiant IRAS 17163-3907. We present the first model-independent reconstructed images of IRAS 17163-3907 at these wavelengths at milli-arcsecond scales. Lastly, we apply a 2D radiative transfer model to fit the dereddened photometry and the radial profiles of published VISIR images at 8.59 μm, 11.85 μm and 12.81 μm simultaneously, adopting the revised Gaia distance (DR2). Results. The interferometric observables around 2 μm show that the Brγ emission is more extended and asymmetric than the Na i and the continuum emission. In addition to the two known shells surrounding IRAS 17163-3907 we report on the existence of a third hot inner shell with a maximum dynamical age of only 30 yr. Conclusions. The interpretation of the presence of Na i emission at closer distances to the star compared to Brγ has been a challenge in various studies. We argue that the presence of a pseudophotosphere is not needed, but it is rather an optical depth effect. The three observed distinct mass-loss episodes are characterised by different mass-loss rates and can inform the theories on mass-loss mechanisms, which is a topic still under debate. We discuss these in the context of photospheric pulsations and wind bi-stability mechanisms.
