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arXiv 0708.2064astro-ph
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一个围绕着大质量主序星MWC 297的演化盘？

An evolved disk surrounding the massive main sequence star MWC 297?

P. Manoj, Paul T. P. Ho, Nagayoshi Ohashi, Qizhou Zhang, T. Hasegawa, Huei-Ru Chen, H. C. Bhatt, N. M. Ashok

备注：
4 pages, 3 Figures, accepted for publication in ApJL
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摘要：

本文介绍了利用亚毫米波阵列在230 GHz（1.3 mm）连续谱和$^{12}$ CO、$^{13}$ CO和C $^{18}$ O（J=2-1）转动跃迁中对MWC 297周围星周盘的干涉观测结果。MWC 297距离我们250 pc，是离我们最近的年轻大质量恒星（M $_{\star}$ $\sim$ 10 M $_{\odot}$）之一。紧凑的连续发射检测到MWC 297，我们估计磁盘质量（气体+灰尘）为0.07 M $_{\odot}$和磁盘半径为$\le$ 80 AU。我们的研究结果表明，星周盘可以生存周围的大质量恒星以及进入其主序星阶段，即使他们已经成为光学可见。补充我们的观察与从文献中汇编的数据，我们发现submm尘埃不透明度指数$β$为0.1和0.3之间。如果发射是光学薄的，则$β$的低值指示盘中存在相对大的晶粒，这可能是由于晶粒生长。我们没有检测到任何CO排放与连续源。我们认为，从磁盘的$^{13}$ CO排放可能是光学薄，在这种情况下，我们推导出的气体质量的上限，这意味着显着耗尽分子气体中的磁盘。这个磁盘的质量和观察到的演化趋势是类似的中等质量赫比格Ae星和低质量金牛T星。

英文摘要：

We present the results of the interferometric observations of the circumstellar disk surrounding MWC 297 in the continuum at 230 GHz (1.3 mm) and in the (J=2-1) rotational transitions of $^{12}$CO,$^{13}$CO and C$^{18}$O using the Submillimeter Array. At a distance of 250 pc, MWC 297 is one of the closest, young massive stars (M$_{\star}$ $\sim$10 M$_{\odot}$) to us. Compact continuum emission is detected towards MWC 297 from which we estimate a disk mass (gas+dust) of 0.07 M$_{\odot}$ and a disk radius of $\le$ 80 AU. Our result demonstrates that circumstellar disks can survive around massive stars well into their main sequence phase even after they have become optically visible. Complementing our observations with the data compiled from the literature, we find the submm dust opacity index $β$ to be between 0.1 and 0.3. If the emission is optically thin, the low value of $β$ indicates the presence of relatively large grains in the disk, possibly because of grain growth. We do not detect any CO emission associated with the continuum source. We argue that the $^{13}$CO emission from the disk is likely optically thin, in which case, we derive an upper limit to the gas mass which implies significant depletion of molecular gas in the disk. The mass of this disk and the evolutionary trends observed are similar to those found for intermediate mass Herbig Ae stars and low mass T Tauri stars.

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