New line-blanketed models for the P-Cygni star HDE 316285 have been calculated. Representative model atoms for H, He I, He II, Ca I, Ca II, Mg I, Mg II, Al II, Al III, Fe II, and Fe III are included in the calculations. We confirm the basic parameters derived by Hillier et al. (1998) in an earlier unblanketed study, and also confirm that many of the optical metal lines are produced by continuum fluorescence. The charge exchange reaction Fe2+ + H ⇌ Fe+ + H + modifies the Fe ionization structure and significantly enhances the strength of the optical Fe II emission lines.

By progress in both computer-speed and the development of efficient solution algorithms (Accelerated Lambda Iteration, ALI) nowadays detailed models for Wolf-Rayet atmospheres can be calculated on a desktop computer. In recent years much work was focused on the correct treatment of all relevant opacities, with the success that now hundreds of atomic levels and thousands of spectral lines of light elements (e.g., He, C, N, O) and millions of Fe lines can be accounted for in non-LTE. With respect to the opacities, these new models are complete but they are all based on the standard assumptions for WR atmospheres, namely spherically-symmetric expansion and stationarity and homogeneity of the outflow (cf. Hamann et al. these Proceedings).

We present the results of simulations which show that stochastic line-profile variations (LPVS) of Wolf-Rayet emission lines can be reproduced with an inhomogeneous wind model, in which line-emission arises from a large number of discrete wind emission elements (DWEES). A comparison between simulations and LPVS from 9 WR stars provides useful information about the nature of the inhomogeneous and dynamical structure of the wind. Although the detailed spatial/fractal structure of the inhomogeneous wind is poorly constrained by analysis of LPVS, simulations suggest the wind to be highly fragmented, being composed of at least 104 DWEES in the line-emission region. Analysis of lpv patterns reaveal DWEES to be associated with large fluctuations in the velocity field. These fluctuations are locally anisotropic; the velocity dispersions of DWEES. are systematically larger in the radial direction (≈vr ≍ 200 km s−1) than in the transverse direction (σvθ ≈ 50 kms−1). lpv patterns also yield estimates of the wind acceleration, which can be used to test hypotheses about the wind velocity-law.

We present here the first results of a grid of helium-carbon-oxygen models for Wolf-Rayet stars of the carbon sequence (WC). The models were calculated with a numerical code that assumes the basic considerations of the standard model.

We discuss the possibility that WR 1 (HD 4004) is a binary system.

Using a dynamical stellar code, detailed evolutionary models have been computed that follow the evolution and nucleosynthesis of massive stars from the pre-MS up through their most advanced stages.

Suppose that the atmosphere of a WC star is formed by clumps embedded in the homogeneous spherically symmetric stellar wind. A single clump may be modeled as a part of the spherical layer restricted with a surface of a cone. Present the gas density in the cone as a sum of gas density in homogeneous atmosphere and gas density in a clump: Here nk(r) is the gas density in the homogeneous atmosphere, Dcl is the ratio of gas densities at a point r = rcl, and δ is the size of the clumps in units rcl.

Shear-turbulence in a radiative envelopes of rotating main sequence massive stars transports angular momentum from the deeper layers to the stellar surface. This process enlarges the influence of rotation on the stellar radius. As a result, the width of the main sequence increases.

We collected photometric data of WR 103 (HD 164270, WC9), both in the Walraven system and in the Strömgren system. Figure 1 presents one intense monitoring run, performed in 1990 by R. van Ojik. We suggest to describe the light-curve as a saw-tooth with a time-scale of roughly 0.5 day. Alhough we confirm a cyclic light-variation of the object with an amplitude of ∼ 0.05 mag, our data do not support the period of P = 0.88 d found by Isserstedt & Moffat (1981) (see also Moffat et al. 1986; Balona et al. 1989).

We studied the short-period (P ≈ 6–8 hr) binary system WR46 using simultaneous photometry and spectroscopy. We show that the long-term photometric variation is accompanied by changes in the equivalent width of the He II Λ5411 emission line and by an apparent period decrease on the rising branch. Furthermore, the brightening of the object is repeating.

We study here the influence of micro-turbulence in the synthesis of H and He lines, in order to quantify its effect on the determination of stellar parameters of O-type stars, in particular on the stellar He abundance. We find that only He I lines and He II λ 4686 are considerably affected, the effect being more relevant for models corresponding to supergiant stars. We also find that neglecting micro-turbulence in the analyses of O-type stars introduces deviations in the derived parameters that are within our standard error box. The He content is not or slightly reduced, thus micro-turbulence cannot be responsible for the He-discrepancy to all its extent.

The supersonic winds of the most luminous stars carry kinetic energy as well as mass. Where such stars are members of binary systems, some of this energy is released in strong shocks which form on both sides of the wind-collision boundary. Originally, the consequent heating of the gas in such systems was predicted to make the stars strong X-ray sources. However, the most conspicuous colliding-wind effects have been observed at longer wavelengths: synchrotron radiation from the shock-accelerated electrons and, most unexpectedly, infrared emission from dust condensing in the shock-compressed gas. Recent developments in observational techniques, especially increased spatial resolution, have led to delineation of these effects, and extensive observing campaigns have given a better idea of their incidence.

It is in the ultraviolet-optical domain where the strongest known emission lines arise in hot star winds. In the case of hot-star binaries, culminating in the relatively common, strong-wind WR+O systems, similar line-emission is seen in the cooling flows downstream from the highly compressed, X-ray emitting heads of the bow shock regions produced when the two winds collide. Time-resolved UV-optical spectroscopy of these flows around a complete orbit can provide important constraints not only on the colliding wind process itself, but also on the winds and the orbit. Spectroscopic wind-wind collision effects have now been seen in every relatively close WR+O system (P ≲ 100 d) that has been adequately observed so far.

We report on recent advances in the modelling of colliding stellar winds in WR binaries. Here, we concentrate on the modelling of X-ray observations using numerical gas-dynamics, in some cases including radiation hydrodynamics, and look in detail at a few systems, such as γ2 Velorum, η Carinae and HD 193793. We also report briefly on the modelling of infrared line-profile variability in a number of close WR+O-star systems, which can reveal further information on the dynamics of the interaction region. We discuss recent 3D-simulations and describe the exciting prospects that AXAF and XMM open up.

We present large scale 3D simulations of colliding winds in the WR binary γ2 Velorum (WR 11). The O-star wind is confined by cold, high density shells and forms a spirally shaped region within the WR-wind. As a consequence of the elliptic orbit, the opening angle and the curvature of the spiral as well as the ratio of the volumes occupied by the WR- and the O-wind are functions of the orbital phase. Our model qualitatively reproduces the observed X-ray light-curve. The impact of magnetic fields and heat conduction on the physics of colliding winds is briefly discussed and some remarks on the important question of stability are made.

The environments of evolved massive stars provide an opportunity of obtaining information on the past, as well as current, condition of the stars themselves. In this review we will look at the incidence of ring nebulae around Wolf-Rayet stars, their differing morphologies at various wavelengths and the existence of multiple, concentric shells. We use this information to show that WRs are indeed evolved stars and that the various phases of evolution for a WR star are evidenced in their environments. Abundance measurements and kinematics show that complex forms of mass ejection are likely to have occurred in the evolution of WR stars providing clumpy structures of dust, and both ionized and neutral gas. Gas kinematics also provide estimates to the time-scales of each of the evolutionary phases of WR stars, which can be combined with estimates of nebular masses to provide the approximate values for such crucial parameters as total mass-loss and historical mass-loss rates. Overall, it is illustrated that studies of the environments of WR stars have the potential to provide important information about the mass-loss history of very massive stars, including estimates of the time period of each mass-loss phase, typical mass loss rates, total mass lost and likely evolutionary path. Some of the remaining problems relating to the use of ring nebulae as probes to the evolutionary history of WR stars are also discussed.

The interaction of the stellar wind of a supersonically moving massive star with its surrounding interstellar medium can result in the formation of an observable bow-shock. Recent studies at optical and infrared wavelengths indicate the presence of wind bow-shocks around several OB runaways, including the high-mass X-ray binary system Vela X-1. A large fraction of runaway stars do not seem to form wind bow-shocks. Obviously, when the local sound speed is high (∼ 100 km s−1), as is the case e.g., inside a hot superbubble, the (subsonic) space velocity would not be sufficient to form a bow-shock. Two-dimensional time-dependent hydrodynamical simulations indicate that the bow-shock is generally unstable; for certain combinations of ISM and wind parameters a bow-shock is not formed at all. The runaway nature of Wolf-Rayet stars in relation to the formation of wind bow-shocks is also discussed.

The formation of ring nebulae and their shapes is studied by numerical simulations. The old problem of the origin of the nebular shape is addressed. Two proposed mechanisms are discussed: stellar rotation and stellar magnetic fields, or a combination of both. Two and three-dimensional hydrodynamical and magneto-hydrodynamical simulations indicate that these processes are equally efficient in driving elliptical nebulae such as those surrounding Wolf-Rayet stars, like NGC 6888 around WR136. However, bipolar nebulae are better reproduced by rotation.

The neutral matter distribution from the interstellar medium located in the vicinity of the galactic WR stars WR 132 and WR 140 has been examined by means of the H I 21-cm line observations obtained with high angular resolution observations. The most interesting discoveries are the presence of huge ovoidal H I minimum spanning the velocity range +13 to +21kms−1 (WR132) and −18 to −7kms−1 (WR 140). These minima were created, very likely, by the joint action of the progenitor of both WR stars and the WR star itself. Inside each cavity, two minima are clearly discernible. The WR star is offset with respect to either the geometrical centre of the main H I void or the inner H I minima. The dual H I minimum geometry observed inside the main H I cavity, a feature also seen in the H I distribution of the ISM located close to other galactic WR stars, may be a consequence of the interaction process itself.

We report the results of long-slit spectroscopy of the wind-blown bubble and photo-evaporating knots around the O6.5IIIf star BD+60°2522 made with the HST-Space Telescope Imaging Spectrograph. The Of star is the primary ionizing source for the H II region NGC 7635, located in the Perseus Arm. The spectra were taken through a 0″.2 x 52″ slit with low and medium resolution gratings covering the wavelength range 2900-6870 Å. Observations with two slit orientations were made; one across the line of embedded knots to the west of the Of star and the second running from the Of star across the bubble to the NE.

The 2D-STIS spectra permit us to subtract the surrounding H II region's diffuse emission from that of the knots and the bubble, and to study the spatial variations in various emission lines in these features to a resolution of ∼ 0″.2, an order of magnitude improvement over the best ground-based spectra of this object in the literature. We present high spatial-resolution emission-line and line-ratio profiles across the bubble and knots, and compare them with the predicted variations from photo-ionization, photo-evaporation, and wind-shock models. We also present an analysis of temperatures, densities, and abundances in the features from higher S/N spectra extracted over selected lengths of the slit.