Observational Study of the Peculiar Carbon Stars with Silicate Emission Features

自1986年发现具有硅酸盐辐射的碳星以来，星周辐射的来源一直困扰着天文学家。我们测量了北方和南方天空中特殊碳星的H_2O和SiO发射。H_2O脉泽只在富氧壳层中观测到。和富氧光球周围的一氧化硅因此，我们的巡天计划是为了回答这个系统中未被发现的富氧星星的问题，利用Nobeyama 45 m和Parkes 64 m望远镜对H_2O进行了观测。我们对这九颗奇特星进行了观测，发现其中两颗星的光谱鉴定是错误的。在剩下的七个天体中，我们已经探测到了三颗恒星的脉泽辐射。通过这次调查，现在确定了富氧的星周壳层的存在。观测中使用了Nobeyama 45 m和ESO/SEST 15 m望远镜。没有一颗特殊的碳星显示出脉泽辐射。SiO脉泽是探测富氧恒星光球层的一个很好的探测器。总之，我们对脉泽辐射的研究证实了星周壳层中的富氧化学，但对特殊碳星星系统中富氧星星的存在提出了疑问。

Since the peculiar carbon stars with silicate emission were found in 1986, astronomers were puzzled about the origin of the circumstellar emission. We have surveyed the H_2O and SiO emission for the peculiar carbon stars in both the northern and southern skies. The H_2O maser is observed only in an oxygen-rich circumstellar shell. and the SiO around an oxygen-rich photosphere. Therefore, our survey was designed to answer the question about the unseen oxygen-rich star in the system.The H_2O observations were carried out using Nobeyama 45m and Parkes 64m telescopes. We have observed all the nine peculiar stars, of which two identifications were found to be wrong from our optical spectroscopic study. Of the remaining seven objects we have detected the maser emission from three stars. The existence of oxygen-rich circumstellar shell is now established by this survey. The high detection rate of 43% indicates that the rapid mass loss is underway in the system.Nobeyama 45m and ESO/SEST 15m telescopes were used in the SiO survey. None of the peculiar carbon stars showed the maser emission. The SiO maser is a good probe for the stellar photosphere with oxygen-rich abundances. The non-detection is against the binary model hypothesis with an oxygen-rich stellar component.In summary, our search for the maser emission confirmed the oxygen-rich chemistry in the circumstellar shell, but cast a question about the existence of the oxygen-rich star in the peculiar carbon star system.