ILLUMINATION IN SYMBIOTIC BINARY STARS - NON-LTE PHOTOIONIZATION MODELS - II - WIND CASE

We describe a non-LTE photoionization code to calculate the wind struc ture and emergent spectrum of a red giant wind illuminated by the hot component of a symbiotic binary system. We consider spherically symmet ric winds with several different velocity and temperature laws and der ive predicted line fluxes as a function of the red giant mass-loss rat e, (M)over dot. Our models generally match observations of the symbiot ic stars EG And and AG Peg for (M)over dot approximate to 10(-8) to 10 (-7) M. yr(-1). The optically thick cross section of the red giant win d as viewed from the hot component is a crucial parameter in these mod els. Winds with cross sections of 2-3 red giant radii reproduce the ob served fluxes because the wind density is then high: similar to 10(9) cm(-3). Our models favor winds with acceleration regions that either l ie far from the red giant photosphere or extend for 2-3 red giant radi i.