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arXiv 0707.0193astro-ph
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低质量年轻恒星TW Hya的高空间分辨率中红外观测

High spatial resolution mid-infrared observations of the low-mass young star TW Hya

Th. Ratzka, Ch. Leinert, Th. Henning, J. Bouwman, C. P. Dullemond, W. Jaffe

备注：
13 pages, 9 figures, accepted by A&A
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摘要：

我们希望提高知识的内部几个AU的拱盘周围附近的金牛座T星TW Hya的结构。早期的研究表明存在一个巨大的内洞，可能是由与一颗正在生长的原行星的相互作用造成的。我们使用了在N波段的干涉观测，这些观测是用甚大望远镜干涉仪上的X射线仪器获得的，再加上红外卫星斯皮策记录的10微米光谱。事实上，我们能够确定N-波段相关通量和vibrations这个相对较弱的源表明，和平号干涉测量可以应用于大量的低质量的年轻恒星物体。斯皮策获得的MIR光谱显示来自HI（6-5），HI（7-6）和[Ne II]的发射线，并表明我们在这个波长范围内看到的尘埃中超过90%是无定形的。根据用射电望远镜测量的相关通量，大部分的晶体物质都在圆盘的内部，未分辨的部分，半径约为1 AU。这个vibrium排除了在TW Hya的拱星盘中存在一个非常大的（3-4 AU半径）内孔，这在早期的模型中是需要的。我们提出了一个几何形状的内盘，其中仍然存在一个内孔，但在一个大大减少的半径，从零到全盘高度之间的过渡0.5和0.8 AU，并与光学薄分布的尘埃内。这样的模型可以符合SED和MIR可见度，以及在2微米的NIR中观察到的可见度和扩展发射。如果一个巨大的行星是这个内洞的原因，正如人们推测的那样，它的轨道必须比0.3 AU更接近恒星。或者，我们可能正在目睹吸积阶段的结束和星周盘向内向外扩散的早期阶段。

英文摘要：

We want to improve knowledge of the structure of the inner few AU of the circumstellar disk around the nearby T Tauri star TW Hya. Earlier studies have suggested the existence of a large inner hole, possibly caused by interactions with a growing protoplanet. We used interferometric observations in the N-band obtained with the MIDI instrument on the Very Large Telescope Interferometer, together with 10 micron spectra recorded by the infrared satellite Spitzer. The fact that we were able to determine N-band correlated fluxes and visibilities for this comparatively faint source shows that MIR interferometry can be applied to a large number of low-mass young stellar objects. The MIR spectra obtained with Spitzer reveal emission lines from HI (6-5), HI (7-6), and [Ne II] and show that over 90% of the dust we see in this wavelength regime is amorphous. According to the correlated flux measured with MIDI, most of the crystalline material is in the inner, unresolved part of the disk, about 1 AU in radius. The visibilities exclude the existence of a very large (3-4 AU radius) inner hole in the circumstellar disk of TW Hya, which was required in earlier models. We propose instead a geometry of the inner disk where an inner hole still exists, but at a much reduced radius, with the transition from zero to full disk height between 0.5 and 0.8 AU, and with an optically thin distribution of dust inside. Such a model can comply with SED and MIR visibilities, as well as with visibility and extended emission observed in the NIR at 2 micron. If a massive planet was the reason for this inner hole, as has been speculated, its orbit would have to be closer to the star than 0.3 AU. Alternatively, we may be witnessing the end of the accretion phase and an early phase of an inward-out dispersal of the circumstellar disk.

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