New light on UU Sagittae *

Abstract

New V- and I-band CCD photometry and medium-resolution spectroscopy are used to derive the masses and radii accurate to <10 percent for the individual components of the eclipsing central star of the planetary nebula Abell 63 – UU Sge.(M1=0.63±0.06 M⊙,R1=0.33±0.01 R⊙,M2=0.29±0.04 M⊙ and R2=0.53±0.02 R⊙).Emission lines from the secondary component and He II and N v absorption features from the primary component are used to determine the first radial velocity curves for the system. Ultraviolet and optical spectra show that the temperature of the primary component is much larger than previously suspected. As the techniques used are essentially model-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.