A pre-outburst of the classical symbiotic star BF Cyg in 1987–1989

Abstract

We analyze previously unpublished spectrophotometric data for the classical symbiotic star BF Cyg obtained in 1982–1989. These data show that BF Cyg already started a new period of activity in 1987–1989, earlier believed to correspond to quiescence. An optical spectrum taken on September 29, 1987 displays several features characteristic of activity in classical symbiotic stars. During the same time interval, excess near-UV radiation was detected, possibly from the accretion disk, and evidence for Rayleigh scattering of the hot component’s radiation on atomic hydrogen was detected in the far-UV, at phases previously believed not to be characteristic of this effect. This latter finding may testify to an enhanced (compared to 1979–1986) rate of mass loss from the cool component of BF Cyg. We discuss the interrelation between an increased mass-loss rate of the cool component and the hot component’s activity in the context of classical symbiotic stars.