Although clearly a peculiar object (Anger 1933), HD 45166 has been the subject of remarkably few published optical studies. Heap & Aller (1978, HA) discuss its optical spectrum and give evidence that the object is a binary system comprising a B8v star and a hotter WR-like object, denoted qWR by van Blerkom (1978). This paper presents the first UV observations of the system obtained with IUE at the epochs listed in Table 1. These new data show drastic line (but not apparently continuum) variations with epoch, which cast doubt on the WR-connection, although herein we still adopt the notation “qWR”.

This paper presents a preliminary study of the IUE UV spectrum of the planetary nebula NGC 40. Details of the observations are given in Table 1 which were obtained in the low resolution (Δλ ∼ 6å) spectrophotometric mode using both SWP (λλ1150–2000) and LWR (λλ1850–3250) spectrographs. All data were acquired using the large (10′x20′) apertures. SWP3076 was taken with the centre of the aperture offset by 7′.5N of the central star: all other images were obtained with the slot centred on the nucleus.

We have started a study of WC central stars of planetary nebulae, including “O VI” objects which show WC characteristics. One of our purposes was to check, all along the WC spectral sequence, if the emission lines of planetary nuclei are narrower than for Population I objects, as they are in the case of the WC9 central star BD+30°3639 (Smith and Aller 1971).

We have used the plate data from An Emission Line Survey of the Milky Way by Parker, Gull and Kirschner(1979) to make a new search for ring nebulae around Wolf-Rayet stars. The Survey consists of narrow-band interference filter direct imagery centered on the emission lines of Hα + [N II] at λ6570, [O III] at λ5007, and [S II] at λ6730. We have discovered at least five new ring nebulae. of the fifteen ring nebulae we were able to detect on the Survey, including our new discoveries, eleven were brighter in the [O III] bandpass than in the Hα + [N II] bandpass, and were filamentary in [O III]. All of the nebulosities we were able to detect were rated on the basis of three criteria:

1. 1) Sharp, filamentary structure present in any or all bandpasses.

2. 2) Wolf-Rayet star centered in projected nebulosity, or, if off-center, the segment of the ring nearest the star proportionally brighter than the rest of the ring.

3. 3) Absence of any O stars within the nebulosity, or O star in off-centered position not adjacent to the brightest or sharpest portion of the ring.

Using strict selection criteria, we have searched for ring nebulae associated with Wolf-Rayet stars in the Galaxy and the Magellanic Clouds. In our search, 15 WR ring nebulae are identified in the Galaxy (Chu 1981a; Chu 1981b, Paper G1), 9 in the Large Magellanic Cloud, and none in the Small Magellanic Cloud (Chu and Lasker 1980, Paper LI; Chu 1981a). We have subsequently observed the morphology and kinematics of these 24 nebulae to study their nature. The data and analyses are reported in G (galactic) and L (LMC) series of papers. These nebulae and their references are listed in Table 1. This table is nearly, but not quite, complete. An extremely careful search might result in more cases, e.g., NGC6357 (Lortet et al. 1981). In a later search by Heckathorn et al. (1982), more ring nebulae are suggested; however, only three cases (associated with HD92740, HD187282, and HD211564) are more convincing. We have obtained some data for these nebulae and will discuss them in a conclusion paper of the galactic series (Chu et al. 1982, Paper G8).

Three cases of ring nebulae around a WC6 star are definitely known : one is around HD 92809 north of the Carina Nebula (Lortet et al. 1980), another around θ Mus has been studied by Heckathorn et al (1982). We here study the third one, NGC 6357 around HD 157504, first quoted in the survey by Heckathorn et al (1981 and 1982).

Preliminary results on the radial velocity field of the ring-shaped nebula N206 in the LMC are given. Several early type stars are located inside this nebula one of them being a WC5-6 star. A discussion about the kinematics of the gas around the WR star is also given.

It is shown that most of usually apparently single nitrogen WR stars with ring emission nebulae around them (WN + Neb) are a probable product of the evolution of a massive close binary with initial masses of components exceeding ∼20 MO.

We have obtained low resolution UV spectrophotometry of the WN-C star HD 62910 in both the SWP (λλ1150–2000) and LWR (λλ1850–3250) IUE spectrographs, and also for HD 117688, WN6, used for comparison. The UV spectrum of HD 62910 is shown in Fig 1 and is seen to be dominated by many strong emission lines, which by comparison with the IUE spectra of other galactic WR stars (Nussbaumer et al. 1981) is found to reflect a predominantly WN-type spectrum, but in addition, weaker features characteristic of WC spectra are also seen, particularly in the LWR wavelength range. In Table 1 we list the principal observed WN and WC features in HD 62910. A comparison of the relative strengths of the WN emissions with those observed in various WN subtypes (Nussbaumer et al. 1981) and with our spectra of HD 117688 confirms the subtype of HD 62910 as WN6 as inferred in the visible (Smith 1968, Van der Hucht et al. 1981).

Results of a statistical analysis of massive stars and of WR stars show general agreement with the scenario that identifies the majority of the WR stars with the He-burning evolutionary phases. The duplicity, the morphological properties and the galactic distribution of the WR stars are valuable pieces of evidence that suggest correlations between the different WR types and the “channels” defined in the scenario. A rough analysis of the “traffic through each channel” is attempted.

Repeated spectra to V-mag 13.0 (13.5) have been obtained since 1978 for the 25 (5) brightest WR stars in the LMC (SMC). More than half of these are orbiting spectroscopic binaries, mainly SB1 for the luminous subclasses WN6-9, and SB2 for the rest. Together with galactic data, the Cloud SB2's lead to a correlation between mass ratio WR/OB and WR spectral subclass for each of the WN and WC sequences. This correlation is interpreted as an evolutionary sequence in which the peeling-off process of the strong stellar wind exposes successively hotter regions and eventually converts WN to WC at a point in time which appears to depend on the ambient metal abundance.

After the systematic survey carried out by Azzopardi and Breysacher (1979, 1980) at La Silla, Chile, with the 40-cm Objective Prism Astrograph, the census of the Wolf-Rayet population (101 stars) in the Large Magellanic Cloud (LMC) can probably be considered as quite complete except, perhaps, for stars located in the core of dense HII regions. The catalogue by Breysacher (1981) includes 100 stars to which one has to add one star of the WN type discovered by Sanduleak (private communication) outside of the survey limits.

November 27, 1980, we had the opportunity to make near infrared observations of a few WR stars of the Magellanic Clouds with the ESO reticon system attached to the Boller and Chivens spectrograph at the 3.6 m telescope. The observing conditions as well as the reduction procedure have been described in another paper of this symposium (Vreux et al., 1982). We will immediately show how the near infra-red can be useful to improve our knowledge of some WR stars.

A search to continuum magnitude B ∼ 21.5 (MB∼ −3) using a narrow band filter at λ4670å and a wide B-band filter has revealed 21 Wolf-Rayet star candidates in about half the giant Sb galaxy M31. Some weak-line WR stars, particularly WN subtypes, may have escaped detection. These numbers are compatible with the total number of luminous (i.e. massive) stars in M31. Eighteen of twenty confirmed candidate stars in M31 lie in the direction of 0B associations in the ring of prominent star formation 5–16 kpc from the center.

We have made a search for line-of-sight coincidences between WR stars and open clusters using the new catalogue of galactic WR stars (van der Hucht et al., 1981, called the HCLS catalogue) and the catalogue of open cluster data (Lyngå and Lundström, 1980). As a measure of the separation we used the angular distance between the WR star and the cluster centre expressed with the cluster angular radius, r', as unit.

Giant HII regions as sites of massive star formation.

Giant HII regions are the brightest extragalactic emission line objects that can be studied in detail. With diameters of several hundreds of parsecs, these nebulae can be easily resolved out to distances of a few Mpc. Typically 100 or more 0 stars are required to account for the observed ionization of the nebular gas and this implies that the cores of giant HII regions contain populous young star clusters. The stars in these clusters have essentially the same age and chemical composition. Thus, giant HII region cores provide excellent sites where theories of the formation and evolution of massive stars and, in particular, of Wolf-Rayet (WR) stars can be tested.

The central cluster of the 30 Doradus complex in the Large Magellanic Cloud (LMC) contains at least a dozen Wolf-Rayet (W-R) stars of the nitrogen sequence according to Melnick (1978). In addition to the six stars previously identified by Feast, Thackeray and Wesselinck (1960), Melnick identified an additional six using an Echele spectrograph on the 1.52 m telescope at La Silla. I have obtained high resolution spectra of ten of these stars and would like to discuss the spectral types.

NGC 604, the largest H II region in M 33, is comparable in many respects (eg. ionized mass, total extent of a few hundered pc) with the giant H II complex 30 Doradus of the LMC. Recently D'Odorico and Rosa (1981) discovered broad WR emission features at 4640 å, 4660 å, He II 4686 å and 5812 å in a number of the bright knots in the core of NGC 604. In that paper it was concluded, that about 50 WR stars, mainly of the transition type WN 7 but WC characteristica seen as well, are present in the H II region. These findings were confirmed by the observations by Conti and Massey (1981).

Data on Wolf-Rayet (WR) stars in extragalactic H II regions and emission line galaxies are presented and discussed. The sample is still limited and inhomogeneous but two important points appear to be already established: a) The WR stars are more numerous than the blue supergiants at least in same phase of the evolution of the stellar clusters which ionize the giant H II regions, b) when the WR stars are detected, two cases are apparently observed, one in which only WN, the other in which both WN and WC, are present.

The 30 Doradus nebula is the brightest H II region in the local group. Radio continuum and Radio recombination line observations indicate that it is photoionized by the equivalent of ∼100 05 stars. Observations of the central object R136 made at low and high spectral resolution with the IUE reveal a peculiar hot object with a massive stellar wind. An outflow speed of 3500 kilometers per second and a temperature of approximately 60,000 K are indicated by the spectra. The bulk of the observed ultraviolet radiation must come from R136a, the brightest and bluest component of R136. Its absolute visual magnitude and observed temperature imply a luminosity about 108 times that of the sun. Most of the ionizations produced in 30 Doradus are provided by this peculiar object. If R136a is a dense cluster of very hot stars, about 30 stars of classes 03 and WN3 exist in a region estimated to have a diameter of less than 0.1 parsec. This is inconsistent with the ultraviolet line spectrum and the evidence for optical variability. An alternative interpretation of the observations is that the radiation from R136a is dominated by a single super-luminous object with the following approximate properties: luminosity and temperature as given above, a radius 100 times that of the sun, a mass 2500 times that of the sun, and a loss rate of 10−3.5 solar masses per year. Model interior calculations for hydrogen-burning stars are consistent with these parameters. Such stars, however, are expected to be unstable, and this may account for the massive stellar wind.