We describe FUSE time-series observations of stellar wind variability in Sk-67°166 (HDE 269698), a nitrogen-rich O4 supergiant in the LMC.

We present the discovery of OB type absorption lines superimposed to the emission line spectrum, and the first double-lined orbital elements, for the massive Wolf-Rayet binary WR 98 (HDE 318016, WN7/C+08-9), a spectroscopic binary in a circular orbit with a period of 47.825 d. The semi-amplitudes of the orbital motion of the emission lines differ from line to line, indicating a mass ratio in the range q ≡ MWR/MOB = 1–1.8.

We present work investigating the stability of line-driven winds using a non-Sobolev approach. We find that the dense shell structures which characterise the growth of radiation-driven instabilities in one dimensional simulations break up into numerous bow-shaped clumps in two-dimensions.

We present preliminary results from observations of the massive WR+O binary WR 22 performed with the XMM-Newton observatory. The star is brighter in the X-ray domain near apastron and fainter at periastron. The change in brightness is very progressive and mainly corresponds to a lowering of the soft part of the spectrum.

Recent non-LTE models for expanding atmospheres, accounting for iron group line-blanketing and clumping, show a radiative acceleration which supplies a large part of the driving force of WR and O star winds. Aiming at the calculation of fully consistent wind models, we developed a method to include the solution of the hydrodynamic equations into our atmosphere code, taking into account the radiation pressure from the CMF radiation transport. In the present work we discuss the resulting wind acceleration for ‘standard’ WR and O-type star model atmospheres, and present a hydrodynamically consistent non-LTE model for the O4I(n)f star ζ Pup. In addition we demonstrate the effect of clumping on the radiative acceleration.

In the present poster paper, we summarize the observational spectroscopic evidence for wind clumping originating in some [WC8-10] and [WO4] central stars of planetary nebulae. Specifically, we concentrate on the C iii λ5696 and C iv λλ5801/12 emission-line variability observed for well-known planetary nebula nuclei.

Since New Year's Eve 1998, we have been studying η Carinae and the surrounding complex ejecta with the HST-stis instrument. Angular resolution of 0.1″ and spectral resolving power R = 5000-118000 have revealed a multitude of emission and absorption lines identified from many heavy elements. Some data was obtained during the 1998.0 spectral minimum and now we have an HST Treasury proposal accepted to follow the star and ejecta changes across the 2003.5 minimum. To date, we identify the Homunculus as an outer reflection nebula, an internal ionized Little Homunculus, a very small shell (0″.74 in diameter), the Weigelt-blobs, and a peculiar structure called the strontium emission filament. More recently an even smaller extended structure (0″.14 diameter) has been found to surround the Central Source as seen in the ultraviolet.

The notorious η Carinae was observed with the stis from 2380 Å to 3160 Å with a resolving power of ~ 130000. Over 500 absorption lines have been identified as originating from Fe i, Fe ii, Ti ii, V ii, Cr ii, Ni ii, Co ii, Mn ii, Mg i and Mg ii. Most of the lines have multiple components ranging from −145kms–1, –385kms–1 to –587kms–1. Many interstellar absorption velocity systems, also found in the spectra of other Carina stars, are seen in the spectrum of η Car. While ISM absorption lines originate from the ground energy level, the nebular lines originate from energy levels well above the ground state. We are still evaluating the origin and location of these velocity systems in line of sight.

The Potsdam non-LTE code for expanding atmospheres, which accounts for clumping and iron-line blanketing, has been used to establish a grid of model atmospheres for WC stars. A parameter degeneracy is discovered for early-type WC models which do not depend on the ‘stellar temperature’. 15 Galactic WC4-7 stars are analyzed, showing a very uniform carbon abundance (He:C = 55:40) with only few exceptions.

We present theoretical X-ray line profiles calculated for a range of model colliding wind systems. In particular we have investigated how the line profiles vary with wind parameters. These profiles will be compared with high-resolution grating spectra of colliding wind binaries and will provide new insights into the structure of the X-ray emitting regions in such systems.

We summarize recent results of magnetic measurements of three bright early B-type stars, β Cep, ζ Cas, and V2052 Oph, which were found to be oblique rotators with a weak magnetic dipole field with typical strength of a few hundred Gauss. From stellar wind studies we could derive their rotational periods very accurately, and match the stellar wind with the magnetic phase. From model atmosphere fits we derive the angles of rotational and magnetic axis. All three stars show some chemical abundance anomaly, presumably associated with the magnetic properties. The stars are also pulsating variables. This is of high asteroseismological interest, since these are the only early-type stars known with observationally determined rotation, pulsation and magnetic properties.

Spectra, providing full phase coverage, of the 19 d WC6+OB binary θ Mus (WR 48, HD 113904), have been obtained and show dramatic variations of the C iii λ5696 emission line profile. We have modeled these line profile variations assuming the winds from the WR star and its close OB companion are colliding and forming a shock region from which extra emission originates.

Spectral analysis of hot stars requires adequate model atmospheres, which take into account the effects of non-LTE and radiation-driven winds properly. Here we present significant improvements of our approach in constructing detailed atmospheric models and synthetic spectra for O-type stars (model code wm-basic; see Pauldrach, Hoffmann & Lennon 2001). The most important ingredients of these models with regard to a realistic description of stationary winds are: (i) a rigorous treatment of line blocking and blanketing; (ii) a consistent determination of the radiative line acceleration; (iii) a considerably improved and enhanced atomic data archive providing the basis for a detailed multilevel non-LTE treatment and an adequate representation of the radiative line driving; and (iv) the inclusion of EUV and X-ray radiation produced by cooling zones originating from shock-heated matter. This new tool not only allows to constrain the properties of stellar winds, the stellar parameters, and the abundances via a comparison of observed and synthetic spectra, but also provides the astrophysically important information about the ionizing fluxes of these stars. We use this new method to compute selfconsistent wind parameters for a series of Galactic stars analyzed in the optical and verify the theoretically predicted dependence of the wind momentum on metallicity.

P Cyg, AG Car, HD 5980 and η Car were observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. FUSE covers the spectral range from 980 Å to 1187 Å at a resolution of 0.05 Å. In this paper we discuss the far-UV properties of these LBVs and explore their similarities and differences. The FUSE observations of P Cyg and AG Car, both spectral type B2pe, are very similar. The atmospheres of both η Car and HD 5980 appear to be somewhat hotter and have much higher ionization stages (Si iv, S iv, and P v) in the FUSE spectrum than P Cyg and AG Car. There is a very good agreement between the FUSE spectrum of P Cygni and the model atmosphere computed by John Hillier with his code cmfgen. The FUSE spectrum of η Car, however, does not agree very well with existing model spectra.

The massive, long-period and highly-eccentric (P = 2899 d, e = 0.88), colliding-wind binary WR 140 (WC7pd+O4-5) may be regarded as a clock-work for its predictable, repeatable IR outbursts related to dust formation right after each periastron passage. However, the 2001 periastron passage broke this monotonic trend. Our UBV photometry, completely covering the past nine years, shows a series of quasi-regular fadings starting ~ 2 months after periastron passage (Φ ≃ 0.02-0.05). Preliminary analysis points to dust as a probable cause of the eclipse-like behavior of the system, while the oscillating pattern hints towards instabilities in the wind-wind collision zone. At the same time, contemporaneous spectroscopy shows nothing unusual aside of the strong, but short-lived signs of wind-wind interaction (Φ ≃ 0.99-1.02).

Line-blanketing effects in atmospheres of O-type stars are studied based on models computed with the non-LTE spherically expanding code cmfgen (Hillier & Miller 1998). We show that the inclusion of metals leads to a reduction of the effective temperature scale by ~ 1500 K at spectral type O9.5, up to ~ 4000 K at spectral type O3. This change of the Teff scale implies a reduction of the luminosity by ~0.1 dex and a decrease of the ionising flux by ~ 50% for a given spectral type.

Absorbing material compressed in a number of thin shells is effectively less opaque for X-rays than smoothly distributed gas. The calculated X-ray emission-line profiles are red-shifted if the emission arises from the starward side of the shells.

We have embarked on a program to directly compare spectroscopic and evolutionary masses with those obtained from a combination of spectroscopic and photometric orbital solutions for O-type binary systems. The ability to directly determine the spectroscopic masses of the individual components of O-type binary systems has been difficult, because of the severe line blending that is present in these systems. Doppler tomography is an iterative scheme, that uses an ensemble of spectra to reconstruct the individual component spectra. These individual spectra can then be analyzed.

We perform X-ray spectral fits to a recently obtained Chandra grating spectrum of η Carinae, one of the most massive and powerful stars in the Galaxy and which is strongly suspected to be a colliding wind binary system. The good fit that we obtain gives us further confidence in the binary hypothesis, and we find M ≈ 2.5 × 10–4 M⊙ yr–1 for the mass loss rate of η Car.

We investigate which shocked wind is responsible for the majority of the X-ray emission in colliding wind binaries, an issue where there is some confusion in the literature, and which we show is more complicated than has been assumed. We find that where both winds rapidly cool (typically close binaries), the ratio of the wind speeds is often more important than the momentum ratio, because it controls the energy flux ratio, and the faster wind is generally the dominant emitter. When both winds are largely adiabatic (typically long-period binaries), the slower and denser wind will cool faster and the stronger wind generally dominates the X-ray luminosity.