High- and low-resolution spectroscopic observations of the peculiar planetary-nebula HD 149427 (=PC 11)

Aims. We discuss the status of the A-type component of the binary central star in the peculiar planetary nebula HD 149427. Methods. We acquired low and high spectral resolution optical spectroscopy for the range 4500-9000 Å. Results. The analysis of the high resolution spectrum shows that the A-type star has an effective temperature of $T_{\rm eff}$ = 8700 ± 150 K and a surface gravity of log g = 2.3 ± 0.4, corresponding to a spectral type A3-A4 II. These parameters infer a luminosity estimate of $\log(L/L_{\odot})$ = 3.69 ± 0.32, implying a distance of 10 ± 0.6 kpc. The A-type star is slightly metal-poor; barium and strontium, two key elements for monitoring the s-process nucleosynthesis, are not enriched; nitrogen is enriched relative to Sun; while carbon and oxygen are underabundant. The photospheric abundance of the A-type giant star in HD 149427 is compared with the abundance in other types of stars at different evolutionary stages