New Light on UU Sagittae

Extract

New V and I band CCD photometry and medium resolution spectroscopy are used to derive the masses, luminosities and radii accurate to < 10% for the individual components of the eclipsing central star of the planetary nebula A63–UU Sge (M₁ = 0.63 ± 0.06M_⊙, R₁ = 0.33 ± 0.01R_⊙, M₂ = 0.29 ± 0.04M_⊙ and R₂ = 0.53 ± 0.002R_⊙). Emission lines from the secondary component and HeII and NV absorption features from the primary component are used to determine the first radial velocity curves of the system. Ultra–violet and optical spectra show that the temperature of the primary compoment is ∼ 10⁵K – much larger than previously suspected. As the techniques used are essentially independent this is probably the most accurately known mass for a planetary nebula central star and therefore allows meaningful comparison to be made with evolutionary tracks for these objects.