Modeling the wind structure of AG Peg by fitting of C IV and N V resonance doublets

Abstract:
The latest outburst of AG Peg has lasted for 150 years, which makes itthe slowest nova eruption ever recorded. During the time of IUEobservations (1978-1995) line profiles and intensity ratios of the N Vand C IV doublet components changed remarkably, and we discuss plausiblereasons. One of them is radiative pumping of Fe II which is investigatedby studying the fluorescence lines from pumped levels. Three Fe IIchannels are pumped by C IV and one by N V. The pumping rates of thoseFe II channels as derived by the modeling agree well with the strengthsof the Fe II fluorescence lines seen in the spectra. We model the C IVand N V resonance doublets in IUE spectra recorded between 1978 and 1995in order to derive optical depths, expansion velocities, and theemissivities of the red giant wind, the white dwarf wind and theircollision region. The derived expansion velocities are ∼60 kms<SUP>-1</SUP> for the red giant wind and ∼700 km s<SUP>-1</SUP> forthe white dwarf wind. We also suggest a fast outflow from the system at∼150 km s<SUP>-1</SUP>. The expansion velocity is slightly higherfor N V than for C IV. Emission from the collision region stronglyaffects the profile of the N V and C IV resonance doublets indicatingits existence.