Abstract
An analysis of the radio continuum spectra of 18 compact planetary nebulae, based on published flux densities plus new observations at 327 MHz with the Westerbork Synthesis Radio Telescope, is presented. It is shown that the radio spectra are well represented by a model in which the radio emission arises in a photon-limited, ionized shell of a stellar wind type envelope. A comparison of predicted and observed angular radii indicates a radial density power law in the shell of the form r exp -2. The model also accounts for an evolutionary trend in the radio spectra revealed by a correlation between spectral shape and the linear dimensions of the nebulae. The results suggest that planetary nebulae are ionized shells of stellar wind ejecta produced during the precursor, red giant stage. The derived mass loss rates are typicaly a few 0.00001 solar masses/yr
Original language | English |
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Pages (from-to) | 178-188 |
Number of pages | 11 |
Journal | Astronomy & Astrophysics |
Volume | 171 |
Issue number | 1-2 |
Publication status | Published - Jan-1987 |