Millimeter observations of vibrationally excited cs toward irc +10216: A new circumstellar maser?

J. L. Highberger, A. J. Apponi, J. H. Bieging, L. M. Ziurys, J. G. Mangum

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

New observations of vibrationally excited CS in its v = 1 state have been conducted toward the circumstellar shell of IRC +10216 using the NRAO 12 m telescope and the CSO. The J = 3 → 2, 6 → 5, and 7 → 6 transitions in the v = 1 level at 146, 292, and 340 GHz have been detected toward this object, and the J = 2 → 1 and 5 → 4 lines were also reobserved. After accounting for contamination from other species, these CS transitions all exhibit line profiles that are narrower (△V1/2 ∼ 10 km s-1) than those displayed by most molecules in IRC +10216, indicating an origin in the inner stellar envelope. The J = 3 → 2 line is particularly narrow (△V1/2 ∼ 10 1-2 km s-1), and consists of two separate velocity components at VLSR ∼ -26 and -22 km s-1. These characteristics are suggestive of weak maser action in this transition. The narrow line widths observed in the other transitions indicate a source size ≲ 0″.5, which implies a CS column density in the v = 1 state of ∼ 2-6 × 1016 cm-2. The ground-state (v = 0) column density is therefore on the order of 0.8-2 × 1018 cm-2 for Tvib = 500 K. The fractional abundance of CS relative to H2 is consequently f ∼ 3-7 × 10-5 at ∼ 14 R *. Such a high abundance close to the stellar photosphere is strong evidence that CS is a "parent" molecule in IRC +10216, as suggested by infrared studies of the v = 0 → 1 vibrational transition and interferometric observations.

Original languageEnglish (US)
Pages (from-to)881-888
Number of pages8
JournalAstrophysical Journal
Volume544
Issue number2 PART 1
DOIs
StatePublished - Dec 1 2000

Keywords

  • AGB
  • Circumstellar matter
  • Masers
  • Radio lines: stars
  • Stars: aGB and post

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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