{
  "id": "1706.09766",
  "version": "v1",
  "published": "2017-06-29T14:03:57.000Z",
  "updated": "2017-06-29T14:03:57.000Z",
  "title": "Detection of Interstellar HC$_5$O in TMC-1 with the Green Bank Telescope",
  "authors": [
    "Brett A. McGuire",
    "Andrew M. Burkhardt",
    "Christopher N. Shingledecker",
    "Sergei V. Kalenskii",
    "Eric Herbst",
    "Anthony J. Remijan",
    "Michael C. McCarthy"
  ],
  "comment": "Accepted in The Astrophysical Journal Letters",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We report the detection of the carbon-chain radical HC$_5$O for the first time in the interstellar medium toward the dark cloud TMC-1 using the 100 m Green Bank Telescope. We observe four hyperfine components of this radical in the $J = 17/2 \\rightarrow 15/2$ rotational transition that originates from the $^2\\Pi_{1/2}$ fine structure level of its ground state, and calculate an abundance of $n/n_{H_2}$ = $1.7\\times 10^{-10}$, assuming an excitation temperature of $T_{ex} = 7$~K. No indication of HC$_3$O, HC$_4$O, HC$_6$O, is found in these or archival observations of the source, while we report tentative evidence for HC$_7$O. We compare calculated upper limits, and the abundance of HC$_5$O to predictions based on (1) the abundance trend of the analogous HC$_n$N family in TMC-1 and (2) a gas-grain chemical model. We find that the gas-grain chemical model well reproduces the observed abundance of HC$_5$O, as well as the upper limits of HC$_3$O, HC$_6$O, and HC$_7$O, but HC$_4$O is over produced. The prospects for astronomical detection of both shorter and longer HC$_n$O chains are discussed.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-06-29T14:03:57.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "green bank telescope",
      "interstellar hc",
      "gas-grain chemical model",
      "upper limits",
      "fine structure level"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}