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Fundamental parameters of Galactic luminous OB stars. IV. The upper HR diagram
Herrero, A.; Puls, J.; Villamariz, M. R.
We present observations and analyses of seven Galactic O stars of type O6 and earlier. The analyses are carried out using NLTE plane-parallel, hydrostatic models as well as NLTE spherical models with mass-loss. With detailed calculations for the former and simulations for the latter, it is shown that the flux blocking due to UV metal lines is impo…
The γ Velorum binary system. II. WR stellar parameters and the photon loss mechanism
Schmutz, W.; Hillier, D. J.; Crowther, P. A. +4 more
In this paper we derive stellar parameters for the Wolf-Rayet star in the gamma Velorum binary system (WR11), from a detailed non-LTE model of its optical and infrared spectra. Compared to the study of Schaerer et al., the parameters of the WC8 star are revised to a hotter effective temperature (T_eff ~ 57 kK), a higher luminosity (log (L/Lsu…
A spectroscopic study of field BHB star candidates
Cacciari, C.; Bragaglia, A.; Castelli, F. +3 more
New spectroscopic observations are presented for a sample of thirty-one blue horizontal branch (BHB) star candidates that are sufficiently nearby to have reliable proper motions. Comments are given on a further twenty-five stars that have previously been suggested as BHB star candidates but which were not included in our sample. Moderately high-re…
Wind properties of Wolf-Rayet stars at low metallicity: Sk 41 (SMC)
Crowther, P. A.
The stellar properties of Sk 41 (AB4, WN5h), the only known single Wolf-Rayet star in the SMC, are derived from ultraviolet (IUE), optical (AAT) and near-IR (NTT) spectroscopy. Contrary to expectations for low metal environments, the stellar properties of Sk 41 are typical of equivalent WN stars in the Galaxy and LMC, with T* ~ 42kK, lo…
NLTE spectral analysis of the sdOB primary of the eclipsing binary system LB 3459 (AA Dor)
Rauch, T.
We present a spectral analysis of the sdOB primary star of the binary system
Strong spectral variability in NGC 7603 over 20 years
Dietrich, M.; Kollatschny, W.; Bischoff, K.
We present results of a long-term optical variability campaign on the Seyfert 1 galaxy NGC 7603 over a period of nearly 20 years. The optical continuum and the Balmer and Helium lines varied by a factor of 5 to 10 in this broad-line Seyfert 1 galaxy. Furthermore, it is remarkable that the optical FeII line blends varied with the same amplitude as …
Abundance in the planetary nebulae NGC 6537 and He2-111
Pottasch, S. R.; Beintema, D. A.; Feibelman, W. A.
The ISO and IUE spectra of the bipolar planetary nebulae NGC 6537 and He2-111 are presented. These spectra are combined with the spectrum in the visual wavelength region from the nebulae to obtain a complete spectrum that is corrected for extinction. The chemical abundance of the nebulae is then determined and compared to previous determinations. …
WN stars in the LMC: Parameters and atmospheric abundances
Hamann, W. -R.; Koesterke, L.
The spectra of 18 WN stars in the Large Magellanic Cloud (LMC) are quantitatively analyzed by means of "standard" Wolf-Rayet model atmospheres, using the helium and nitrogen lines as well as the spectral energy distribution. The hydrogen abundance is also determined. Carbon is included for a subset of 4 stars. The studied sample covers all spectra…
Ultraviolet fluorescence lines of Fe II observed in satellite spectra of the symbiotic star RR Telescopii
Johansson, S.; Hartman, H.
By examining all emission lines of Fe II in high resolution satellite spectra of the symbiotic star RR Tel we have made a systematic study of fluorescence lines in the ultraviolet wavelength region 1200-3000 Ä. We list 33 energy levels of Fe II that are selectively excited in the stellar system by photons from strong lines of H, He II, Si III, O I…
T Tauri stars: The UV/X-ray connection
Costa, V. M.; Lago, M. T. V. T.; Norci, L. +1 more
We have analysed newly calibrated IUE and ROSAT data for three T Tauri stars from different subclasses: TW Hya, V410 Tau and CS Cha, a Classical T Tauri star (CTTS), a Weak T Tauri star (WTTS) and a T Tauri star intermediate between CTTS and WTTS, respectively. In the ultraviolet the continuum seems to be well explained by the sum of the stellar b…