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arXiv 0907.2102astro-ph.SR
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关于Herbig Ae/Be星盘中耀斑和阴影的相互作用

On the interplay between flaring and shadowing in disks around Herbig Ae/Be stars

B. Acke, M. Min, M. van den Ancker, J. Bouwman, B. Ochsendorf, A. Juhasz, R. Waters

备注：
4 pages, 3 figures, accepted by A&A
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摘要：

根据SED，赫比格星被分为两个观测组，反映了它们的整体盘结构：第一组成员的盘比第二组成员的盘有更高程度的耀斑。我们研究了13个I组源和20个II组源的5-35 μ m Spitzer IRS谱。我们专注于连续辐射来研究潜在的盘的几何形状。我们已经确定了[30/13.5]和[13.5/7]连续通量比。7微米的通量过剩相对于恒星光球测量，作为近红外线发射的强度由内盘产生的标记。我们已经比较了我们的数据自洽被动盘模型光谱，其中相同的数量。我们证实了文献的结果，即第一组和第二组源之间的连续发射的差异可以在很大程度上解释了不同数量的小尘埃颗粒。然而，我们报告的[30/13.5]和[13.5/7]之间的相关性很强的Meeus第二组源的流量比。此外，[30/13.5]通量比随着样品中所有靶的7 μ m过量的增加而降低。为了解释这些与模型的相关性，我们需要引入一个人工的内盘高度比例因子。在我们的样本中，大约50%的赫比格Ae/Be星，内盘必须膨胀2到3倍，超出流体静力学计算的预测。小尘埃颗粒中的总盘质量决定了耀斑的程度。然而，我们的结论是，对于任何给定的磁盘质量的小尘埃颗粒，阴影的外（几十个天文单位）磁盘是由内部磁盘的规模高度（1天文单位）。内盘部分遮挡了外盘，降低了盘表面温度。在这里，我们第一次证明了这些效果的观测。

英文摘要：

Based on the SED, Herbig stars have been categorized into two observational groups, reflecting their overall disk structure: group I members have disks with a higher degree of flaring than their group II counterparts. We investigate the 5-35 um Spitzer IRS spectra of a sample of 13 group I sources and 20 group II sources. We focus on the continuum emission to study the underlying disk geometry. We have determined the [30/13.5] and [13.5/7] continuum flux ratios. The 7-um flux excess with respect to the stellar photosphere is measured, as a marker for the strength of the near-IR emission produced by the inner disk. We have compared our data to self-consistent passive-disk model spectra, for which the same quantities were derived. We confirm the literature result that the difference in continuum emission between group I and II sources can largely be explained by a different amount of small dust grains. However, we report a strong correlation between the [30/13.5] and [13.5/7] flux ratios for Meeus group II sources. Moreover, the [30/13.5] flux ratio decreases with increasing 7-um excess for all targets in the sample. To explain these correlations with the models, we need to introduce an artificial scaling factor for the inner disk height. In roughly 50% of the Herbig Ae/Be stars in our sample, the inner disk must be inflated by a factor 2 to 3 beyond what hydrostatic calculations predict. The total disk mass in small dust grains determines the degree of flaring. We conclude, however, that for any given disk mass in small dust grains, the shadowing of the outer (tens of AU) disk is determined by the scale height of the inner disk (1 AU). The inner disk partially obscures the outer disk, reducing the disk surface temperature. Here, for the first time, we prove these effects observationally.

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