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On the nature of the material surrounding VEGA
Harper, D. A.; Loewenstein, R. F.; Davidson, J. A.
AA(Chicago, University, Chicago, IL), AB(Chicago, University, Chicago, IL), AC(Chicago, University, Chicago, IL)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 285, Oct. 15, 1984, p. 808-812. (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
A Stars, Far Infrared Radiation, Infrared Astronomy Satellite, O Stars, Poynting-Robertson Effect, Stellar Envelopes, Black Body Radiation, Fourier Transformation, Water Vapor
Bibliographic Code:


Observations of Vega at 193 microns indicate that the far-infrared emission from the circumstellar material discovered by IRAS (Aumann et al. 1984) may decline more rapidly than a Planck spectrum at wavelengths greater than 100 microns. This suggests that the emitting particles may be smaller than the millimeter-sized objects proposed by Aumann et al. (1984). Small grains would be driven from the stellar system by radiation pressure, or their orbits would decay as a result of Poynting -Robertson drag. In order to maintain a state of dynamic equilibrium, a continuous supply of new particles would be required. It is hypothesized that the small grains are ejected by sublimation of volatile material from larger comet-like bodies in a partially coalesced preplanetary disk. A reservoir containing less than a few hundred earth masses could sustain the source over the lifetime of the star.

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