Abstract
Of forty-seven planetaries for which measurements have been made of angular radii, H β fluxes, relative line intensities and central star magnitudes, forty-two are shown to satisfy criteria for complete absorption in the continua of H I , of He I or of He II . For these forty-two nebulae values are obtained for the central star temperatures T , for the luminosity parameter Λ = L / r2L where r is the distance, and for a parameter η which provides a measure of the completeness of absorption in the H I Lyman continuum. It is found that for thirteen of them absorption in the Lyman continuum is complete, or practically complete. The star temperatures range from 2.8 × 10 4 °K to 1.8 × 10 6 °K.

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