Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry
Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry
复制标题
基于VLTI/AMBER光谱干涉测量的红超巨星VY Canis Majoris的基本特性和大气结构
DOI：
10.1051/0004-6361/201219126
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发表时间：
2012
影响因子：
6.5
通讯作者：
J. Marcaide
中科院分区：
文献类型：
--
作者：
M. Wittkowski;P. Hauschildt;B. Arroyo;J. Marcaide
目标。我们研究了红超巨星VY CMa的大气结构和基本性质。方法.我们获得了近红外光谱干涉观测VY CMa光谱分辨率为35和1500使用的AMBER仪器在VLTI。结果可见度数据表明，在扩展大气中存在水汽和CO的分子层，具有不对称的形态。与2.20 - 2.25µm的近连续带通相比，2.0µm附近的水带中的均匀圆盘直径增加了20%，而在2.3 - 2.5µm的CO带中，它增加了高达50%。封闭阶段表示相对较小的偏离接近光球层的点对称性，和较强的偏差在扩展的H2O和CO层。利用其高的空间和光谱分辨率，可以将近连续带与分子层和尘埃层的污染隔离开来，并根据PHOENIX大气模式估算出Rosseland平均光球角直径为11.3± 0.3mas。结合最近对距离和分光光度学的高精度估计，这个估计对应于半径为1420±120 R，有效温度为3490±90 K。结论. VY CMa表现出不对称的，可能cloudly，大气层的H2O和CO，这是不合作的空间，在一个更大的细长的尘埃信封。我们修改后的基本参数使VY CMa接近最近演化轨道的Hayashi极限，即在HR图中向蓝演化之前不久，初始质量为25 M（有旋转）或32 M（无旋转）。
Aims. We investigate the atmospheric structure and fundamental properties of the red supergiant VY CMa. Methods. We obtained near-infrared spectro-interferometric observations of VY CMa with spectral resolutions of 35 and 1500 using the AMBER instrument at the VLTI. Results. The visibility data indicate the presence of molecular laye rs of water vapor and CO in the extended atmosphere with an asymmetric morphology. The uniform disk diameter in the water band around 2.0µm is increased by∼20% compared to the nearcontinuum bandpass at 2.20‐2.25µm, and in the CO band at 2.3‐2.5µm it is increased by up to∼50%. The closure phases indicate relatively small deviations from point symmetry close to the photospheric layer, and stronger deviations in the extended H2O and CO layers. Making use of the high spatial and spectral resolution, a near-continuum bandpass can be isolated from contamination by molecular and dusty layers, and the Rosseland-mean photospheric angular diameter is estimated to 11.3±0.3 mas based on a PHOENIX atmosphere model. Together with recent high-precision estimates of the distance and spectro-photometry, this estimate corresponds to a radius of 1420±120 R⊙ and an effective temperature of 3490±90 K. Conclusions. VY CMa exhibits asymmetric, possibly clumpy, atmospheric layers of H2O and CO, which are not co-spatial, within a larger elongated dusty envelope. Our revised fundamental parameters put VY CMa close to the Hayashi limit of recent evolutionary tracks of initial mass 25 M⊙ with rotation or 32 M⊙ without rotation, shortly before evolving blueward in the HR-diagram.