Fe II Fluorescence in Symbiotic Stars

Abstract

AbstractFe II fluorescence by PAR has been investigated in eight symbiotic stars having a wide range in temperature of the hot component and orbital period. The data used are spectra obtained from the IUE archive. All pumping lines investigated in this work are in the short wavelength region of IUE (1200-2000 Å), except for He ɪɪ λ1084.942 and O VI λ1032.041. The resulting Fe ɪɪ fluorescence lines are mainly in the long wavelength region (2000-3300 Å), but a few fall in the same region as the pumping lines. The aim is to understand the optimal conditions for formation of Fe ɪɪ fluorescence lines caused by PAR. Three of the selected systems, RR Tel, AG Peg and V1016 Cyg, have 10-30 active Fe ɪɪ channels. Two conditions connect those systems to each other: The hot component is a white dwarf of extreme temperature (80·103-150·103 K) and all three systems are so called symbiotic novae and have had outbursts during the last 150 years. Three systems, AG Dra, RW Hya and R Aqr, have only 2-3 active Fe ɪɪ channels. In the two remaining systems, CI Cyg and T CrB, Fe ɪɪ fluorescence lines were totally absent. These two systems have two features in common: The emission strength of highly ionized elements is less than in most symbiotic systems, and the hot component is suspected to be an accreting main sequence star rather than a white dwarf.