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Ly-α Radiation Densities in Planetary Nebulae

Published online by Cambridge University Press:  14 August 2015

Eugene R. Capriotti
Eugene R. Capriotti*
Affiliation:
Perkins Observatory, Ohio State and Ohio Wesleyan Universities, U.S.A.

Extract

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The average Ly-α radiation densities are calculated for 9 planetary nebulae from the observed λ 10830/λ5876 line-intensity ratios under the assumption that the 23S state of He I is depopulated via photo-ionization by Ly-α radiation. Three of the nebulae are probably optically thick in their respective hydrogen Lyman continua. For these objects, the Ly-α radiation densities as determined from the λ10830/λ5876 line-intensity ratios may represent the actual Ly-α radiation densities. If they do, then the Ly-α radiation pressures exceed the respective gas pressures in these objects. For the remaining nebulae, it seems that the observationally determined Ly-α radiation densities are representative only if either one or both of the following conditions is fulfilled in each case:

  1. (1) The object is essentially optically thick in the hydrogen Lyman continuum when other properties show it to be optically thin in the hydrogen Lyman continuum.

  2. (2) We are viewing the object during a specific 100-year time span during the course of its evolution.

Type
Session III – Physical Processes
Information
Symposium - International Astronomical Union , Volume 34: Planetary Nebulae , 1968 , pp. 185 - 189
Copyright
Copyright © Reidel 1968 

References

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