Search Publications
The Galactic WN stars. Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation
Hamann, W. -R.; Gräfener, G.; Liermann, A.
Context: .Very massive stars pass through the Wolf-Rayet (WR) stage before they finally explode. Details of their evolution have not yet been safely established, and their physics are not well understood. Their spectral analysis requires adequate model atmospheres, which have been developed step by step during the past decades and account in their…
Physical parameters and wind properties of galactic early B supergiants
Crowther, P. A.; Lennon, D. J.; Walborn, N. R.
We present optical studies of the physical and wind properties, plus CNO chemical abundances, of 25 O9.5-B3 Galactic supergiants. We employ non-LTE, line blanketed, extended model atmospheres, which provide a modest downward revision in the effective temperature scale of early B supergiants of up to 1-2 kK relative to previous non-blanketed result…
Keplerian discs around post-AGB stars: a common phenomenon?
Waters, L. B. F. M.; Dejonghe, H.; de Ruyter, S. +3 more
Aims.We aim at showing that the broad-band SED characteristics of our sample of post-AGB stars are best interpreted, assuming the circumstellar dust is stored in Keplerian rotating passive discs.Methods.We present a homogeneous and systematic study of the Spectral Energy Distributions (SEDs) of a sample of 51 post-AGB objects. The selection criter…
First detection of Lyman continuum escape from a local starburst galaxy. I. Observations of the luminous blue compact galaxy Haro 11 with the Far Ultraviolet Spectroscopic Explorer (FUSE)
Östlin, G.; Zackrisson, E.; Bergvall, N. +3 more
Context: .The dominating reionization source in the young universe has not yet been identified. Possible candidates include metal poor dwarf galaxies with starburst properties.Aims.We selected an extreme starburst dwarf, the Blue Compact Galaxy Haro 11, with the aim of determining the Lyman continuum escape fraction from UV spectroscopy.Methods.Sp…
Reduced Wolf-Rayet line luminosities at low metallicity
Crowther, P. A.; Hadfield, L. J.
New NTT/EMMI spectrophotometry of single WN2-5 stars in the Small and Large Magellanic Clouds are presented, from which He ii λ4686 line luminosities have been derived, and compared with observations of other Magellanic Cloud Wolf-Rayet stars. SMC WN3-4 stars possess line luminosities which are a factor of 4 times lower than LMC counterparts, inco…
Quantitative spectroscopy of BA-type supergiants
Butler, K.; Kudritzki, R. P.; Przybilla, N. +1 more
Luminous BA-type supergiants have enormous potential for modern astrophysics. They allow topics ranging from non-LTE physics and the evolution of massive stars to the chemical evolution of galaxies and cosmology to be addressed. A hybrid non-LTE technique for the quantitative spectroscopy of these stars is discussed. Thorough tests and first appli…
On the AU Microscopii debris disk. Density profiles, grain properties, and dust dynamics
Augereau, J. -C.; Beust, H.
Context: .
Modeling of PMS Ae/Fe stars using UV spectra
Blondel, P. F. C.; Djie, H. R. E. Tjin A.
Context: .Spectral classification of AeFe stars, based on visual observations, may lead to ambiguous conclusions.
Aims: . We aim to reduce these ambiguities by using UV spectra for the classification of these stars, because the rise of the continuum in the UV is highly sensitive to the stellar spectral type of A/F-type stars.
Methods: . …
Resolving the compact dusty discs around binary post-AGB stars using N-band interferometry
Waters, L. B. F. M.; Jaffe, W.; Paresce, F. +8 more
We present the first mid-IR long baseline interferometric observations of the circumstellar matter around binary post-AGB stars. Two objects,
A high-resolution spectroscopy survey of β Cephei pulsations in bright stars
Uytterhoeven, K.; De Ridder, J.; Aerts, C. +4 more
We present a study of absorption line-profile variations in early-B type near-main-sequence stars without emission lines. We have surveyed a total of 171 bright stars using the Nordic Optical Telescope (NOTSA), William Herschel Telescope (ING) and Coudé Auxiliary Telescope (ESO). Our sample contains 75% of all O9.5-B2.5 III-V non-emission-line sta…