The Eclipse of the Symbiotic Star BF CYG

Like SY Mus and EG And, BF Cyg is another classical symbiotic system where the effects of Rayleigh scattering can be observed close to eclipse. Here we re-analyzed the ultra-violet observations made by lUE between 1979 and 1989 in order to study the continuum variations due to eclipse effects. We concluded that besides Rayleigh scattering as source of continuum opacity acting at the cool giant star's extended atmosphere, another source of opacity wavelength independent could act at other phases in BF Cyg. We also give estimates of extinction factors, as was defined in Pereira et al. [A&A, 293, 783 (1995)], and the variation of the column density of the neutral hydrogen against phase. The observed variation between the cycles 1979-1981 and 1986-1989 could be, in principle, attributed to some modification the in the giant's wind.