Fe II fluorescence in symbiotic stars

Abstract:
Fe 0 fluorescence by PAR has been investigated in eight symbiotic starshaving a wide range in temperature of the hot component and orbitalperiod. The data used are spectra obtained from the IUE archive. Allpumping lines investigated in this work are in the short wavelengthregion of IUE (1200-2000 Å), except for He 0 λ 1084.942 andO 0 λ 1032.041. The resulting Fe 0 fluorescence lines are mainlyin the long wavelength region (2000-3300 Å), but a few fall in thesame region as the pumping lines. The aim is to understand the optimalconditions for formation of Fe 0 fluorescence lines caused by PAR. Threeof the selected systems, RR Tel, AG Peg and V1016 Cyg, have 10-30 activeFe 0 channels. Two conditions connect those systems to each other: Thehot component is a white dwarf of extreme temperature (80 .10<SUP>3</SUP>-150 . 10<SUP>3</SUP> K) and all three systems are socalled 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 0channels. In the two remaining systems, CI Cyg and T CrB, Fe 0fluorescence lines were totally absent. These two systems have twofeatures in common: The emission strength of highly ionized elements isless than in most symbiotic systems, and the hot component is suspectedto be an accreting main sequence star rather than a white dwarf.