THE INCIDENCE OF NON-SPHERICAL CIRCUMSTELLAR ENVELOPES IN ASYMPTOTIC GIANT BRANCH STARS

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 out...

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Bibliographic Details
Published in:The Astrophysical journal 2011-11, Vol.741 (1)
Main Authors: Politano, Michael, Taam, Ronald E.
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ASYMMETRY
BASIC INTERACTIONS
BINARY STARS
COMPUTERIZED SIMULATION
GIANT STARS
GRAVITATIONAL INTERACTIONS
INTERACTIONS
NEBULAE
PLANETARY NEBULAE
SIMULATION
STARS
STELLAR ACTIVITY
STELLAR WINDS
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Summary: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{sub sun} in systems with orbital separations of 3-30 AU 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.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/741/1/5;COUNTRYOFINPUT:INTERNATIONALATOMICENERGYAGENCY(IAEA)