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

¹ University College of Kalmar, 391 82 Kalmar, Sweden
² Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden e-mail: mattias@astro.lu.se

Received: 16 July 2003
Accepted: 31 March 2004

Abstract

The latest outburst of AG Peg has lasted for 150 years, which makes it the slowest nova eruption ever recorded. During the time of IUE observations (1978-1995) line profiles and intensity ratios of the N V and C IV doublet components changed remarkably, and we discuss plausible reasons. One of them is radiative pumping of Fe II which is investigated by studying the fluorescence lines from pumped levels. Three Fe II channels are pumped by C IV and one by N V. The pumping rates of those Fe II channels as derived by the modeling agree well with the strengths of the Fe II fluorescence lines seen in the spectra. We model the C IV and N V resonance doublets in IUE spectra recorded between 1978 and 1995 in order to derive optical depths, expansion velocities, and the emissivities of the red giant wind, the white dwarf wind and their collision region. The derived expansion velocities are ~60 km s^-1 for the red giant wind and ~700 km s^-1 for the white dwarf wind. We also suggest a fast outflow from the system at ~150 km s^-1. The expansion velocity is slightly higher for N V than for C IV. Emission from the collision region strongly affects the profile of the N V and C IV resonance doublets indicating its existence.