High- and low-resolution spectroscopic observations of the peculiar planetary-nebula HD 149427 (=PC 11)
Pereira, C. B.; Miranda, L. F.; Daflon, S.; Baella, N. O.
Brazil, Spain
Abstract
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 Teff = 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⊙) = 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.