BVRIJHK photometry of post-AGB candidates: evolution of post-AGB central stars

Abstract

Post-AGB stars are generally believed to be on their way to the planetary nebula stage. However, there has been a question about the evolutionary path for the low-mass ones. We present BVRIJHK photometry of post-AGB candidates selected on their IRAS colors. Their spectral energy distributions showed that 16 out of 27 objects were very likely to be the post-AGB stars. Two objects were remarkable in that their central stars were of rather late spectral type while their dynamical ages of their detached dust shell were considerably older than the others. We believe they are low mass post-AGB stars dispersing their dust shells which will not become planetary nebula but will directly evolve to white dwarfs.