{
  "id": "1506.06551",
  "version": "v1",
  "published": "2015-06-22T11:12:39.000Z",
  "updated": "2015-06-22T11:12:39.000Z",
  "title": "Methanol Observation of IRAS 19312+1950: A Possible New Type of Class I Methanol Masers",
  "authors": [
    "Jun-ichi Nakashima",
    "Andrej M. Sobolev",
    "Svetlana V. Salii",
    "Yong Zhang",
    "Bosco H. K. Yung",
    "Shuji Deguchi"
  ],
  "comment": "20 pages, 4 figures, 8 tables. PASJ in press",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We report the result of a systematic methanol observation toward IRAS 19312+1950. The properties of the SiO, H2O and OH masers of this object are consistent with those of mass-losing evolved stars, but some other properties are difficult to explain in the standard scheme of stellar evolution in its late stage. Interestingly, a tentative detection of radio methanol lines was suggested toward this object by a previous observation. To date, there are no confirmed detections of methanol emission towards evolved stars, so investigation of this possible detection is important to better understand the circumstellar physical/chemical environment of IRAS 19312+1950. In this study, we systematically observed multiple methanol lines of IRAS 19312+1950 in the lambda=3mm, 7mm, and 13mm bands, and detected 6 lines including 4 thermal lines and 2 class I maser lines. We derived basic physical parameters including kinetic temperature and relative abundances by fitting a radiative transfer model. According to the derived excitation temperature and line profiles, a spherically expanding outflow lying at the center of the nebulosity is excluded from the possibilities for methanol emission regions. The detection of class I methanol maser emission suggests that a shock region is involved in the system of IRAS 19312+1950. If the central star of IRAS 19312+1950 is an evolved star as suggested in the past, the class I maser detected in the present observation is the first case detected in an interaction region between an evolved star outflow and ambient molecular gas.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-06-22T11:12:39.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "evolved star",
      "methanol emission regions",
      "radio methanol lines",
      "systematic methanol observation",
      "methanol maser emission"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}