eta Car从1968年到2018年的中红外演变
Mid-infrared evolution of eta Car from 1968 to 2018
摘要：
Eta Car是我们银河系中最明亮和质量最大的恒星之一，也是太阳系外天空中最明亮的中红外（中红外）源。自20世纪90年代末以来，中心光源在紫外线和光学波长处显着变亮。这可能是由于星周尘埃灭绝的减少。我们的目标是建立中红外通量的演变，并进一步了解恒星的紫外线和光学增亮。来自$8-20~μ$ m的中红外图像是在2018年用甚大望远镜的VISIR获得的。2003年和2005年的档案数据来自ESO科学档案设施，历史记录来自出版物。我们提出了最高的角分辨率中红外图像的$η$汽车到目前为止，在相应的波长（$\geq 0.22''$）。我们重建了1968年至2018年空间整合的Homunculus星云光谱能量分布的中红外演化，没有发现长期变化。Eta Car的热辐射光度在过去的五十年里一直保持稳定。我们没有观察到中红外线通量密度的长期下降，这可能与紫外线和光学波长的增亮有关，但星周尘埃必须只在我们的视线范围内下降。短期通量变化可能在平均水平的25%左右。
英文摘要：
Eta Car is one of the most luminous and massive stars in our Galaxy and is the brightest mid-infrared (mid-IR) source in the sky, outside our solar system. Since the late 1990s the central source has dramatically brightened at ultraviolet and optical wavelengths. This might be explained by a decrease in circumstellar dust extinction. We aim to establish the mid-IR flux evolution and further our understanding of the star's ultraviolet and optical brightening. Mid-IR images from $8-20~μ$m were obtained in 2018 with VISIR at the Very Large Telescope. Archival data from 2003 and 2005 are retrieved from the ESO Science Archive Facility and historical records are collected from publications. We present the highest angular resolution mid-IR images of $η$ Car to date at the corresponding wavelengths ($\geq 0.22''$). We reconstruct the mid-IR evolution of the spectral energy distribution of the spatially integrated Homunculus nebula from 1968 to 2018 and find no long-term changes. Eta Car's bolometric luminosity has been stable over the past five decades. We do not observe a long-term decrease in the mid-IR flux densities that could be associated with the brightening at ultraviolet and optical wavelengths, but circumstellar dust must be declining in our line-of-sight only. Short-term flux variations within about 25% of the mean levels could be present.
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