The abundance distribution of C4H in IRC + 10216

Aditya Dayal, John H. Bieging

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

We have observed the N = 9-8 spin doublet emission line of C4H at 85.6 GHz in the carbon star IRC + 10216 with the BIMA millimeter interferometer. The aperture synthesis images have an angular resolution of ∼10″ and a velocity resolution of ∼1.3 km s-1. The data clearly show that C4H is distributed in a shell surrounding the central star, with little emission from the inner envelope. The peak of the average radial brightness profile in a map centered at the systemic velocity and with a width of 10 km s-1 is ∼0.88 K at a projected radius of 15″. From the brightness temperature profile we infer that the thickness of the shell at half-peak intensity is ∼15″. We derive the abundance of the molecule as a function of distance from the star using an LTE model. The peak abundance is calculated to be 1.8 ×10-6 (with respect to the H2 number density) at a radius of 16″.7 or 2.5 × 1016 cm assuming a distance of 100 pc, a mass-loss rate of 2 × 10-5 M yr-1, and an outflow velocity of 13.8 km s-1. We compare our derived C4H distribution with the predictions of a photochemical model and find that the model underestimates the observed abundance of C4H by a factor of 5.

Original languageEnglish (US)
Pages (from-to)L37-L40
JournalAstrophysical Journal
Volume407
Issue number1 PART 2
DOIs
StatePublished - Apr 10 1993

Keywords

  • Molecular processes
  • Stars: carbon
  • Stars: circumstellar matter
  • Stars: mass loss

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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