The planetary nebula K 1-2 and its binary central star VW Pyx

Abstract

New data are presented of the post-common-envelope binary VW Pyx and its associated planetary nebula (PN), K 1-2. The central star is found to be a single-lined (and possibly double-lined) spectroscopic binary and is a good candidate for a system in which the main-sequence secondary star is more massive than the subdwarf primary star. The old PN has a high excitation level and a measured electron temperature, T_O~ 17 000 K for an assumed log n_e= 2.7 cm^-3. The so-called `jets' are found to be lower-ionization regions with T_N~ 11 000 K and T_O~ 16 000 K with log n_e~ 2.5 cm^-3 and with low, but fairly typical, PN abundances. We discuss possible histories for K 1-2 and the jets. However, there are still many unknowns in the study of accretion and jet formation for such PN binary central stars.