在2.3微米CO谱线上空间分辨红巨星大角星的热不均匀外层大气
Spatially resolving the thermally inhomogeneous outer atmosphere of the red giant Arcturus in the 2.3 micron CO lines
摘要：
K巨星的外层大气具有热不均匀结构，由热的色球气体和冷的分子气体组成。我们目前的光谱干涉观测的多组分外大气的K1.5巨大的大角星（α Boo）在CO的第一泛音线附近2.3微米。我们在甚大望远镜干涉仪（VLTI）上用AMBER仪器在2.28- 2.31微米处观测大角星，光谱分辨率为12000，投影基线为7.3，14.6和21.8米。VLTI/琥珀仪器的高光谱分辨率使我们能够在空间上解决大角星在个别CO线。观测到的干涉数据与MARCS光球模型的比较表明，该恒星似乎比模型预测的要大得多。它表明存在一个扩展的组件，这是不占目前的光球模型，这一良好的研究明星。我们发现，所观察到的AMBER数据可以解释的模型与两个额外的CO层以上的光球。内CO层位于光球层上方，恒星半径为1.04 +/- 0.02，温度为1600 +/- 400 K，CO柱密度为10^{20 +/- 0.3} cm^-2。另一方面，我们发现CO外层延伸到2.6 +/- 0.2恒星半径，温度为1800 +/- 100 K，CO柱密度为10^{19 +/- 0.15} cm^-2。内CO层的性质与先前从空间未分辨光谱分析中推断的那些基本一致。然而，我们的ABER观测表明，准静态冷分子成分延伸到2- 3个恒星半径，在该区域内色球风急剧加速。
英文摘要：
The outer atmosphere of K giants shows thermally inhomogeneous structures consisting of the hot chromospheric gas and the cool molecular gas. We present spectro-interferometric observations of the multicomponent outer atmosphere of the well-studied K1.5 giant Arcturus (alpha Boo) in the CO first overtone lines near 2.3 micron. We observed Arcturus with the AMBER instrument at the Very Large Telescope Interferometer (VLTI) at 2.28--2.31 micron with a spectral resolution of 12000 and at projected baselines of 7.3, 14.6, and 21.8 m. The high spectral resolution of the VLTI/AMBER instrument allowed us to spatially resolve Arcturus in the individual CO lines. Comparison of the observed interferometric data with the MARCS photospheric model shows that the star appears to be significantly larger than predicted by the model. It indicates the presence of an extended component that is not accounted for by the current photospheric models for this well-studied star. We found out that the observed AMBER data can be explained by a model with two additional CO layers above the photosphere. The inner CO layer is located just above the photosphere, at 1.04 +/- 0.02 stellar radii, with a temperature of 1600 +/- 400 K and a CO column density of 10^{20 +/- 0.3} cm^-2. On the other hand, the outer CO layer is found to be as extended as to 2.6 +/- 0.2 stellar radii with a temperature of 1800 +/- 100 K and a CO column density of 10^{19 +/- 0.15} cm^-2. The properties of the inner CO layer are in broad agreement with those previously inferred from the spatially unresolved spectroscopic analyses. However, our AMBER observations have revealed that the quasi-static cool molecular component extends out to 2--3 stellar radii, within which region the chromospheric wind steeply accelerates.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
