EVOLUTION OF THE SYMBIOTIC BINARY-SYSTEM AG PEGASI - THE SLOWEST CLASSICAL NOVA ERUPTION EVER RECORDED

We present an analysis of new and existing photometric and spectroscop ic observations of the ongoing eruption in the symbiotic star AG Pegas i. These observations show that this binary has evolved considerably s ince the turn of the century. In particular, recent dramatic changes i n both the UV continuum and the wind from the hot component allow a mo re detailed analysis than in previous papers. AG Peg is composed of a normal M3 giant (M(g) approximately 2.5M. and a hot, compact star (M(h ) approximately 0.6M.) embedded in a dense, ionized nebula. The hot co mponent powers the activity observed in this system, including a dense wind (v(r) approximately 1000 km s-1; M approximately 10(-6) M. yr-1) and a photoionized region within the outer atmosphere of the red gian t. The hot component contracted in radius at roughly constant luminosi ty from 1850 to 1985. Its bolometric luminosity declined by a factor o f approximately 4 during the past 5 yr, and it may now be evolving alo ng the constant radius portion of the white dwarf cooling curve. Both the mass loss rate from the hot component and the emission activity de creased in step with the hot component's total luminosity, while photo spheric radiation from the red giant companion remained essentially co nstant.