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arXiv 1111.1813astro-ph.SR
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一个年轻恒星天体的第一次凯克零化观测：探测赫比格Ae星MWC 325的星周环境

First Keck Nulling Observations of a Young Stellar Object: Probing the Circumstellar Environment of the Herbig Ae star MWC 325

S. Ragland, K. Ohnaka, L. Hillenbrand, S. T. Ridgway, M. M. Colavita, R. L. Akeson, W. Cotton, W. C. Danchi, M. Hrynevych, R. Millan-Gabet, W. A. Traub

备注：
Accepted for publication in the ApJ
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摘要：

我们提出了第一个N波段零加上K-和L-波段V2观测的一个年轻的恒星对象，MWC 325，采取与85米基线凯克干涉仪。凯克零室是为研究与碎片盘有关的微弱尘埃特征而设计的，但它也有一种独特的能力，可以研究在年轻恒星物体周围发现的较致密盘的温度和密度分布。MWC 325在K，L和N的干涉测量观测在光谱范围内包含五个因子，因此，特别是当光谱分散在每个波段内时，能够表征行星形成的内盘区域的结构。将我们的观测结果与几何模型（如均匀圆盘或高斯圆盘）拟合表明，在2-12 μ m波长范围内，表观尺寸随波长单调增加，证实了基于辐射转移模型的广泛假设，现在在宽波长范围内进行了空间分辨测量，即圆盘随温度梯度延伸。与K带相比，L带和N带中的有效尺寸分别大约1.3倍和2倍。现有的干涉测量和光谱能量分布可以通过平盘或弱阴影的近平盘模型再现，在盘的外部区域中仅具有轻微的闪耀，由具有代表性的“亚微米”（0.1 μ m）和“微米”（2 μ m）颗粒组成，硅酸盐和石墨的比例为50：50。这与以前在其他赫比格Ae/Be星中发现的盘形成鲜明对比，表明赫比格Ae/Be星之间的盘属性存在很大差异。

英文摘要：

We present the first N-band nulling plus K- and L-band V2 observations of a young stellar object, MWC325, taken with the 85 m baseline Keck Interferometer. The Keck nuller was designed for the study of faint dust signatures associated with debris disks, but it also has a unique capability for studying the temperature and density distribution of denser disks found around young stellar objects. Interferometric observations of MWC 325 at K, L and N encompass a factor of five in spectral range and thus, especially when spectrally dispersed within each band, enable characterization of the structure of the inner disk regions where planets form. Fitting our observations with geometric models such as a uniform disk or a Gaussian disk show that the apparent size increases monotonically with wavelength in the 2-12 um wavelength region, confirming the widely held assumption based on radiative transfer models, now with spatially resolved measurements over broad wavelength range, that disks are extended with a temperature gradient. The effective size is a factor of about 1.3 and 2 larger in the L-band and N-band, respectively, compared to that in the K-band. The existing interferometric measurements and the spectral energy distribution can be reproduced by a flat disk or a weakly-shadowed nearly flat-disk model, with only slight flaring in the outer regions of the disk, consisting of representative "sub-micron" (0.1 um) and "micron" (2 um) grains of a 50:50 ratio of silicate and graphite. This is marked contrast with the disks previously found in other Herbig Ae/Be stars suggesting a wide variety in the disk properties among Herbig Ae/Be stars.

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