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arXiv 0704.0463astro-ph
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TWA 7碎片盘的质量和温度

Mass and Temperature of the TWA 7 Debris Disk

B. C. Matthews, P. G. Kalas, M. C. Wyatt

摘要:

我们目前的光度探测尘埃排放在850和450微米周围的前主序列M1矮TWA 7使用SCUBA相机的詹姆斯克拉克麦克斯韦望远镜。这些数据证实了TWA 7周围存在冷尘埃盘,TWA 7是TW Hydrae协会的成员。基于850微米的通量,我们估计圆盘的质量为18个月球质量(0.2个地球质量),假设质量不透明度为1.7平方厘米/克,温度为45 K。这使得TWA 7盘(d=55 pc)比显微镜座AU(GL 803)周围的盘大一个数量级,显微镜座AU(GL 803)是在M矮星周围检测到的最接近(9.9 pc)的碎片盘。这与TWA 7比AU Mic稍年轻一致。我们发现,中红外和亚毫米数据需要磁盘在一定温度范围内的灰尘组成。在一个模型中,尘埃是在一个单一的半径从恒星,根据颗粒大小的温度范围,是有效的拟合发射光谱作为一个模型中,尘埃是均匀的大小,但有一个温度范围根据距离。我们讨论这个磁盘在TW长蛇座协会和低质量恒星周围的已知磁盘的背景下,在TWA磁盘的质量的比较显示没有趋势的质量或演化状态(丰富的气体与碎片)作为光谱类型的函数。

英文摘要:

We present photometric detections of dust emission at 850 and 450 micron around the pre-main sequence M1 dwarf TWA 7 using the SCUBA camera on the James Clerk Maxwell Telescope. These data confirm the presence of a cold dust disk around TWA 7, a member of the TW Hydrae Association. Based on the 850 micron flux, we estimate the mass of the disk to be 18 lunar masses (0.2 Earth masses) assuming a mass opacity of 1.7 cm^2/g with a temperature of 45 K. This makes the TWA 7 disk (d=55 pc) an order of magnitude more massive than the disk reported around AU Microscopii (GL 803), the closest (9.9 pc) debris disk detected around an M dwarf. This is consistent with TWA 7 being slightly younger than AU Mic. We find that the mid-IR and submillimeter data require the disk to be comprised of dust at a range of temperatures. A model in which the dust is at a single radius from the star, with a range of temperatures according to grain size, is as effective at fitting the emission spectrum as a model in which the dust is of uniform size, but has a range of temperatures according to distance. We discuss this disk in the context of known disks in the TW Hydrae Association and around low-mass stars; a comparison of masses of disks in the TWA reveals no trend in mass or evolutionary state (gas-rich vs. debris) as a function of spectral type.

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