Pseudo Resonance Absorption Lines in Planetary Nebulae - Discovery

Abstract

The possibility of the formation of pseudo-resonance absorption lines in planetary nebulae is predicted only theoretically. However, this has not been confirmed by direct observations. In the present article an attempt has been made to show, as a result of careful analysis of IUE spectral recordings for a group of planetary nebulae, that the existence of one pseudo-resonance line 1300 <SiIII> is without doubt at least in spectra of three planetary nebulae: NGC 2610, NGC 3587, and NGC 6891. The presence of this line in the spectra of the other three planetary nebulae, NGC 6210, IC 3568, and IC 4776, seems to be probable. The role of the interstellar selective absorption, the blending effect by the resonance lines of SiII,OI, andSI in the formation of the pseudo-resonance line 1300 <SiIII> as well as the possibility of formation of this line in the photosphere of central star of nebula were analysed.