We study the problem of a wind ejected from a star which orbits around a (wind-less) companion star. The orbital motion induces the formation of a spiral shock structure in the wind. An analytic formulation of the problem allows us to obtain the distance from the star at which the shock waves appear, and also the locus of the spiral, two-shock structure (i.e., the working surface). The full, three-dimensional structure of the working surface is found to have a spiral intersection with the orbital plane, and a cylindrical “hole” around the polar axis.

NGC 2359, a H II region located at a distance of 5 kpc from the Sun (e.g., Goudis et al. 1994), appears as a ring like nebula surrounding HD 56925, a Wolf-Rayet star of type WN4. The nebula consists of a filamentary shell, a southern bar and streamers of diffuse gas (cf. Schneps et al. 1981, SHWB). Here we report the results of H I 21-cm line and radio continuum observations in the direction of NGC 2359.

SN1997ab belongs to a class of luminous type II SNe which are thought to be powered by the interaction of the shock wave with a dense circumstellar medium. We report the discovery of narrow P-Cygni profiles atop broad Balmer emission lines, an unambiguous signature of a dense and slow circumstellar wind due to mass loss in the final stages of the progenitor's life.

Wolf-Rayet stars are losing mass via their strong winds. Some of them show thermal and non-thermal radio emission and from this group some have companions forming binary systems. It has been suggested that the synchrotron emission arises from the interaction region where the winds of the two stars collide. WR 147 seems to be one of these systems, having a companion and emitting thermal as well as non-thermal radiation. Besides, it has been suggested that it has an anisotropic wind. In the present work we continue studying the WR 147 system by observing it at a radio wavelength of 3.6 cm in two different epochs. We have looked for evidence to support the idea that WR 147 is a colliding-wind binary system. We have also looked for time variations in the source during the time interval of ∼ 1.4 years separating our observations.

Using both MERLIN and the VLA, we have succeeded in detecting the radio emission from three components in WR 146: the WR star, the wind-wind collision region, and for the first time, the stellar companion to the WR star. This allows the unique possibility of determining the mass loss rate ratio of the two winds, an important observable that is independent of distance.

Radio observations of Wolf-Rayet stars currently available in the literature are examined to determine whether binarity is a common feature of WR systems with non-thermal emission. Among 24 stars with observed spectral index values, seven are definite non-thermal emitters, and six others possibly have composite thermal/non-thermal spectra. Stellar companions have been identified in 71% of the non-thermal emitters, strongly supporting a link between non-thermal emission and binarity.

We report the results of a re-analysis of KPNO-IRS spectroscopy of 30 locations in the prototypical WR shell nebula NGC 6888 (WN6 central star). The spectra covered a 3500–7200 Å wavelength range with R ≃ 360 effective spectral resolution. Electron temperatures for a majority of the locations were derived from the [N II] λλ(6548+6583)/5755 and the [O III] λλ(4959+5007)/4363 emission line ratios. Te([N II]) ≃ 8000 ± 2400 K for eleven locations in the north and west parts of the shell and Te([N II]) ≃ 13 000 ± 4000 K for five locations in the southwest part. By contrast, the [O III] temperatures show great variation with location, ranging from 12000 K to 55000 K, with the highest value being that for an [O III] filament located to the north and outside of the ensemble of knots defining the northern extent of the mass loaded ejecta from the star.

Using a combination of spectral ‘arithmetic’, shock- and photoionization models, we demonstrate that NGC 6888 is permeated by a strong hot wind-shocked gaseous medium (which extends outside the mass-loaded ejected material in the north and west) that contaminates the spectrum of any given location and must be removed to determine realistic Te, Ne, and abundances for the ejected material in the observed knots. For some knots, the effects are such that the abundances obtained via naive empirical methods were found to be several times too small (particularly for O/H) than in reality. We present a few illustrative examples and discuss the implications the results have on abundances previously derived for NGC 6888, but more importantly, what these results imply about the origin of temperature fluctuations in other types of nebulae which may be influenced by stellar winds (i.e., planetary nebulae and H II regions).

A new approach to 3D optically thick non-LTE radiative transfer for moving media is presented. As a first application, we look at the ionization state of the colliding winds interaction zone between two stars.

WR30a (MS 4) was first suspected as a possible Wolf-Rayet star by McConnell & Sanduleak (1970) during a deep objective-prism survey performed around the Carina Nebula region. From subsequent studies, the spectrum turned out to be composite, with a WR component classified W04 (or alternatively WC4, W05 and WC3) and an 0 component classified 04. Niemela (1995) reported the first, and up-to-now unique, radial velocity study for that star. She noticed large variations of CIV λ4658 from night to night, suggesting that WR30a might be a short period binary. A plot of the C IV emission-line velocities versus the He II absorption ones clearly indicates that they are exhibiting opposite binary motions. The apparent velocity amplitudes imply a rather low mass ratio Mwo4/Mo4 = 0.15, although the radial velocities of the C IV line could be distorted due to line-profile variations.

First results concerning the HST-Hα imaging of M1-67 are found in Grosdidier et al. (1998). With the étalon of the Université Laval (Québec), we have obtained complementary Fabry-Pérot Hα data using CFHT-OSIS (August 1996, seeing ≃ 0′′.6, FSR ≃ 392 km s−1, 5.9 kms−1 velocity sampling, see Figure 1). From these data, M1-67 appears more-or-less as a spherical shell seen almost exactly along its direction of rapid spatial motion in the ISM (Moffat et al. 1982). The radial velocity of the center of expansion is rv 137kms−1 (Sirianni et al. 1998). Instead of appearing as a nice hollow-type shell projected on the sky, we probably see the cap of the bow-shock nearly straight on from behind. The far side is greatly intensity-enhanced compared to the near side, probably as a result of raming with the ISM. This was already claimed by Solf & Carsenty (1982). The bright bullets (see Grosdidier et al. 1998) are possibly, after all, Rayleigh-Taylor instabilities seen along the line of sight at or near the bow-shock head, as they slightly ‘fall’ back towards the star. More details will be found in Grosdidier et al. (1999 in preparation).

We present four epochs of high-resolution IR spectroscopy of the peculiar X-ray binary Cygnus X-3. The observations cover quiescent, small flaring and outburst states of the system as defined by radio and X-ray monitoring. The underlying IR spectrum of the source, as observed during radio and X-ray quiescence and small flaring states is one of broad, weak He II and N V emission. Spectral variability in this state is dominated by modulation at the 4.8 hr orbital period of the system. H-band spectra confirm the significant hydrogen depletion of the mass donor. In outburst, the infrared spectrum is dramatically different, with the appearance of very strong twin-peaked He I emission displaying both day-to-day variability and V (iolet) / R(ed) variations with orbital phase. We argue that the most likely explanation appears to be an enhanced stellar wind from the companion. Thus the X-ray and radio outbursts in this system are likely to originate in mass-transfer, and not disc instabilities. We suggest that the wind in Cyg X-3 is significantly flattened in the plane of the binary orbit. This may explain the observed twin-peaked He I features as well as reconcile the large infrared luminosity with the large optical depth to X-rays if Cyg X-3 is embedded in a spherically symmetric wind.

It is crucial to better understand the winds from massive stars. Not only does their mass loss affect their own evolution but it contributes an amount of energy and momentum to the ISM capable of affecting the chemical and dynamical evolution of their environments. Hot star binaries offer an opportunity to learn more. Colliding winds in such systems might be expected to lead to a bow shock which wraps around the star with the weaker wind. As material flows along the shock, it may give rise to extra line emission. Variations in these emission features may allow the characteristics of the shock region to be deduced thus providing a wealth of information about the winds.

Detailed analysis of the phase-dependent line-profile variations of IUE observations γ2 Velorum it is found that selective absorption by the wind is the dominant source of variation in the UV. Excess emission from the shock zone also contributes but this too is selectively absorbed.

Using IUE-SWP spectra, an orbital solution is derived for both components in the γ2 Velorum, which supports the lower mass of the O star found previously.

A detailed kinematical analysis of wind-blown bubble ring nebula NGC 6888 swept-up by the wind of the Wolf-Rayet star WR 136, combining high resolution echelle [O III] spectra, high resolution HST imaging and high resolution ground base imaging, is presented. The kinematics is compared to new theoretical models for the dynamics of WR bubbles based on a three-winds scenario. The actual visible nebula is formed by the red supergiant wind swept-up by the fast WR wind. We conclude that the intringuing filamentary morphology, mainly formed by clumps, tails and ripples are explained by the actuation of Vishniac instabilities on the swept-up shell during the expansion of a red supergiant wind, as predicted by the gas dynamical simulations. The kinematics confirm that NGC 6888 is actually on a breakout process at the NW side, as derived from the blowouts. The blowouts are formed by shocked gas which is directly interacting with the cavity formed by the main sequence wind. The fact that these blowouts are bounded by shocks suggests that the cooling is efficient in a main sequence bubble during the evolution.

We have resolved, for the first time in any WR+OB system, IR-emitting dust in the close environment of the long-period binary WR 137. The dust emission occurs in a few clumps within about 0″.5 of the star, as well as in a jet-like structure with total extension of about 0″.25.

We present the first 12CO 1→0 emission-line maps of the vicinities of two Wolf-Rayet stars (WR 16 and WR 75) and their associated ring nebulae. We illustrate that sizeable amounts of molecular gas appear associated with these ring nebulae and therefore that the mass of gas in ring nebulae is significantly higher than inferred from observations of the ionized gas component alone. We discuss the possible stellar and interstellar origins of these molecular materials and the implications for the evolution of massive stars up to the WR phase.

We present a kinematical study of ring nebulae surrounding Wolf-Rayet stars in the Local Group galaxy M 33, based on Fabry-Perot data obtained at the CFHT. Most of these rings show evidence for multiple phases of mass ejection from the central star. Variations are noted in the [OIII]/Hα emission-line ratios across several ring nebulae generally associated a variation in kinematics. Significant [O III] emission appears to arise from the collision between the fast WR wind and surrounding ejecta from a prior phase, such as a RSG or LBV.

High resolution optical spectra of the planetary nebula Abell 78 were gathered, covering the wavelength ranges 3500–6600 Å and 3358–7361 Å, with a spectral resolution of ∼0.1 Å. Two different regions of Abell 78 are analyzed: the strongest knot near the central star which is thought to be a mass-loaded wind from the central star, and the outer, hydrogen-rich envelope. Physical parameters and chemical composition of both regions are estimated. The inner knot appears to be cooler and denser than the hydrogen-rich envelope. The chemical composition of the inner knot shows that there is almost no hydrogen near the central star and the emission is dominated by helium and processed material which has been dredged-up from the inner layers of the star. The outer, hydrogen-rich envelope appears to be deficient in heavy elements, mainly in oxygen, compared to the average abundances that are found among galactic planetary nebulae.

The timing of PNe formation around low-mass WC stars is unsettled with respect to pulsations early in the post-AGB phase, or later thermal pulses (e.g., Tylenda & Gorny 1997). The chemistry of the dust in the nebulae can be used to trace the mass-loss history. Using ISO-SWS spectroscopy, the PNe BD+30°3639 [WC9] and He2–113 [WC11] have been identified by Waters et al. (1998) to exhibit emission from C-rich dust (PAHs) in the surrounding envelopes at λ 15 μm, while O-abundant silicate features are present at longer wavelengths. Figure 1 shows the PAH features, which include additional WCPNe observations to extend the range of stellar spectral subtypes.