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星際與拱星介質

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CO(2-1) emission from carbon star R Scl

圖片來源: Ding-V-Trung et al.

CO(2-1) emission from carbon star R Scl imaged with the SMA. A clumpy shell is clearly seen in all velocity channels. The shell has a dynamical timescale of ~1600 years. The emission closer to the center represents a more recent episode of mass loss. (Din

We have used the SMA to image the distribution of CO gas through its rotational transition J=2-1 around carbon star R Scl. The high angular resolution image obtained with the SMA reveals an almost spherical, hollow and highly clumpy shell of molecular gas around R Scl, which is located at the center of the image (Figure 1). The molecular detached shell imaged by the SMA also closely matches the dust shell seen previously in scattered light. The result clearly indicates that this star experienced a very short episode of intense mass loss. The mass loss process only resumes quite recently as evidenced by the presence of faint emission closer to the center. From the angular size and expansion velocity of the shell we can infer that the shell was ejected about 1600 years ago. The cause of this massive ejection of matter is still unclear but could be related to the explosive helium flashes, which are theoretically predicted to occur periodically in evolved stars such as R Scl.