Artículos de revistas
UV spectral analysis of very hot H-deficient [WCE]-type central stars of planetary nebulae: NGC 2867, NGC 5189, NGC 6905, Pb 6 and Sand 3
Fecha
2014Registro en:
Monthly Notices of the Royal Astronomical Society, Oxford, v. 442, p. 1379-1395, 2014
0035-8711
10.1093/mnras/stu878
Autor
Rodrigues, Graziela Roswitha Keller
Bianchi, Luciana
Maciel, Walter Junqueira
Institución
Resumen
We analysed ultraviolet Far Ultraviolet Spectroscopic Explorer, International Ultraviolet
Explorer, and Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra of
five of the hottest [WCE]-type central stars of planetary nebulae: NGC 2867, NGC 5189,
NGC 6905, Pb 6, and Sand 3. The analysis leveraged on our grid of CMFGEN synthetic spectra,
which covers the parameter regime of hydrogen-deficient central stars of planetary nebulae
and allows a uniform and systematic study of the stellar spectra. The stellar atmospheremodels
calculated by us include many elements and ionic species neglected in previous analyses, which
allowed us to improve the fits to the observed spectra considerably and provided an additional
diagnostic line: the Ne VII λ973 Å, which had not been modelled in [WCE] spectra and which
presents, in these stars, a strong P-Cygni profile. We report newly derived photospheric and
wind parameters and elemental abundances. The central stars of NGC 2867, NGC 5189, and
Pb 6 had their temperatures revised upward in comparison with previous investigations and
we found the carbon to helium mass ratio of the sample objects to span a wide range of values,
0.42 < C : He < 1.96. Modelling of the Ne VII λ973 Å P-Cygni profile indicated strong neon
overabundances for the central stars of NGC 2867, NGC 5189, NGC 6905, and Pb 6, with Ne
mass fractions between 0.01 and 0.04. Nitrogen abundances derived by us for the central stars
of NGC 5189, Pb 6, and Sand 3 are higher than previous determinations by factors of 3, 10,
and 14, respectively.