IALP   13078
INSTITUTO DE ASTROFISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
Improved spectral descriptions of planetary nebulae central stars
Autor/es:
WEIDMANN WALTER A.; MÉNDEZ ROBERTO; GAMEN, R.
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP SCIENCES S A
Referencias:
Lugar: Paris; Año: 2015 vol. 447 p. 86 - 96
ISSN:
0004-6361
Resumen:
Context. At least 492 central stars of Galactic planetary nebulae(CSPNs) have been assigned spectral types. Since many CSPNs are faint,these classification efforts are frequently made at low spectralresolution. However, the stellar Balmer absorption lines arecontaminated with nebular emission; therefore in many cases alow-resolution spectrum does not enable the determination of the Habundance in the CSPN photosphere. Whether or not the photosphere is Hdeficient is arguably the most important fact we should expect toextract from the CSPN spectrum, and should be the basis for an adequatespectral classification system. Aims: Our purpose is to provideaccurate spectral classifications and contribute to the knowledge ofcentral stars of planetary nebulae and stellar evolution. Methods: We have obtained and studied higher quality spectra of CSPNsdescribed in the literature as weak emission-line star (WELS). Weprovide descriptions of 19 CSPN spectra. These stars had been previouslyclassified at low spectral resolution. We used medium-resolution spectrataken with the Gemini Multi-Object Spectrograph (GMOS). We providespectral types in the Morgan-Keenan (MK) system whenever possible. Results: Twelve stars in our sample appear to have normal H richphotospheric abundances, and five stars remain unclassified. The rest(two) are most probably H deficient. Of all central stars described byother authors as WELS, we find that at least 26% of them are, in fact, Hrich O stars, and at least 3% are H deficient. This supports thesuggestion that the denomination WELS should not be taken as a spectraltype, because, as a WELS is based on low-resolution spectra, it cannotprovide enough information about the photospheric H abundance.