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

C. B. Pereira¹, N. O. Baella¹, S. Daflon¹ and L. F. Miranda²

¹ Observatório Nacional-MCT, Rua José Cristino, 77. CEP 20921-400 São Cristóvão, Rio de Janeiro-RJ, Brazil e-mail: [claudio;baella;daflon]@on.br
² Instituto de Astrofísica de Andalucía, CSIC, Apdo. 3004, 18080 Granada, Spain e-mail: lfm@iaa.es

Received: 8 April 2009
Accepted: 5 August 2009

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  = 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  = 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.