A preliminary analysis of the planetary nebula central star V477 Lyrae.

Abstract

We present a preliminary analysis of V477 Lyr, the eclipsing central star of Abell 46. Medium-resolution spectroscopy has been obtained, providing radial-velocity measurements for both components for the first time. New V-band charge coupled devices (CCD) photometry has also been obtained and the first full light-curve analysis is presented. The solution suggests M₁ = 0.51 +/- 0.07 stellar mass, R₁ = 0.17 +/- stellar radius, M₂ = 0.15 +/- 0.02 stellar mass and r₂ 0.46 +/- 0.03 stellar radius. Comparison of the properties of the primary component with published evolutionary tracks suggests that it may be an example of a 'lazy PN', where the central star is visually bright while the nebula itself has a low surface brightness. As in the case of UU Sge, the secondary component is found to be oversized for its mass. In both systems this situation can be understood in terms of an expansion of the cool star caused by the accretion of a small quantity of material (much less than 1 stellar mass) on to its surface, which is most likely to have occurred during a recent common-envelope phase. It is shown that all the close-binary planetary nebula nuclei that have been analysed sufficiently well are unlikely to evolve into catacylsmic binaries in the next 10¹⁰ yr, unless a more efficient method of losing orbital angular momentum is found.