The incidence of non-spherical circumstellar envelopes in asymptotic giant branch stars

Michael Politano*, Ronald E. Taam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

The relative occurrence of asymmetric structures in the circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars in detached binary star systems is studied based on a population synthesis method. The effects of envelope shaping by the gravitational interaction of the companion on an outflowing stellar wind are incorporated using previously derived empirical fits to numerical simulations. It is shown that significant asymmetries in the CSE, characterized by a ratio of the density in the equatorial direction relative to the polar direction, can exceed 10 for AGB stars characterized by luminosities in the range of 1000-10, 000 L in systems with orbital separations of 3-30AU and mass ratios of 0.25-1. The incidence of such systems relative to a present-day field population of AGB stars (single + binary) is estimated to be 1%-6%, depending upon input parameter choices. For more modest density contrasts exceeding a factor of two, the incidence increases to 4%-15%. With the advent of future high-resolution molecular line studies of CSEs with the Atacama Large Millimeter Array, it is anticipated that the number of AGB stars exhibiting detectable asymmetries will significantly increase.

Original languageEnglish (US)
Article number5
JournalAstrophysical Journal
Volume741
Issue number1
DOIs
StatePublished - Nov 1 2011

Keywords

  • binaries: general
  • circumstellar matter
  • planetary nebulae: general
  • stars: AGB and post-AGB
  • stars: mass-loss
  • stars: winds, outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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