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中央研究院天文及天文物理研究所
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The Theoretical Astrophysics (Theory)

The Incidence of Non-spherical Circumstellar Envelopes in AGB Stars
Image Credit: Politano and Taam
The Incidence of Non-spherical Circumstellar Envelopes in AGB Stars
The figures show the number of systems (color coded) for a degree of asymmetry, as measured by K, as a function of the orbital separation, luminosity, mass of the AGB star, and mass of its companion.
The asymmetric structure of planetary nebulae are common and may, in part, be a result of asymmetries present in the circumstellar envelopes of asymptotic giant branch (AGB) stars in detached binary star systems. A study determining the relative occurrence of such asymmetries in AGB systems has been carried out based on a population synthesis method. Envelope shaping by the gravitational interaction of a binary companion on the stellar wind is used to show that significant asymmetries in the envelope are expected for AGB stars more luminous than 1000-10,000 solar luminosities in systems with orbital separations of 3-30 AU and mass ratios of 0.25-1. (Politano and Taam 2011, ApJ, 741, 5)
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