Emission-line galaxies contain a large number of hot stars responsible for the emissive gas. They offer the opportunity of investigating the initial mass function of stars in regions of active star formation. So far, only integral properties of the ionizing complexes in giant H II regions or emission-line galaxies have been used (Lequeux et al., 1981) but no direct emission-line stellar feature has been thoroughly analyzed.

The size of typical errors in log L/L⊙ and log Teff is investigated for WR stars, and it is found that typically Δ log L/L⊙ = ±(0.25 ± 0.03), and Δ log Teff = ±(0.05 ± 0.02). The major sources of error are the uncertainties in the distance modulus of the star and the integrated continuous flux from about 1400 å to 1 µm or so. The same is true for O and early B stars. With uncertainties of these sizes in log L/L⊙ and log Teff, it is unreliable to estimate the mass of an early-type star from its observed position in the HR diagram. The WN7/8 stars lie with the O9/B0 Ia stars, the other WR stars with the B0/B1 III stars.

Each of four WR binaries has been observed in the 0.1 −5 keV range on four consecutive days for a total of ∼ 104 sec with the IPC on the Einstein Observatory. One of the stars is the well-known WN5 + 06 binary V444 Cyg; the other three have suspected compact companions; all have periods close to four days.

Neither HD 197406 (WN7) nor HD 96548 (WN8) was detected; hence Lx (0.5–3.0 keV) ≲ 1032 erg s−1, which is on the low side, even for 0-stars. EZ CMa (WN5) and V444 Cyg are moderately strong, variable X-ray sources with Lx (0.5–3.0 keV) ≃ 1033 erg s−1, kT ≃ 0.5 keV and NH ≃ 1022 cm−2. These values suggest that the X-ray flux arises in the outer part of the wind. The variable component may be produced by collision of two winds.

There is no evidence of harder X-rays coming from accretion onto a compact star. Nevertheless, the presence of a collapsar is not excluded at hv ≲ 5 keV, where absorption in the WR wind would likely reduce the X-ray flux to a level which is masked by the flux coming from the hot stellar wind.

The ratio of binaries among the WR stars is subject of many discussions essentially due to two reasons: First, the important role that the presence of a companion can play in the evolution of a massive star and as consequence in the interpretation of the evolutionary phase of the WR stars. Second, the strong difficulty to determine the binarity of the WR stars due to the width of the spectral lines.

Preliminary results of three X-ray surveys are presented. Out of a sample of 20 stars, X-rays were detected from four Wolf-Rayet stars and two 08f+ stars. The detected stars have about the same mean value as 0 stars for the X-ray to total luminosity ratio, LX/L = 10−7, but exhibit a much larger variation about the mean. The spectral energy distributions are also found to be like that of 0 stars in that they do not exhibit large attenuation of X-rays softer than 1 keV. This indicates that for both the 0 stars and WR stars much of the X-ray emission is coming from hot wisps or shocks in the outer regions of the winds and not from a thin source at the base of the wind. The general spectral shape and flux level place severe restrictions on models that attribute the lack of hydrogen emission lines to extremely high temperatures of the gas in the wind.

The task I have would appear to be an impossible one. The assembled company is to be congratulated. In the ten years since the last WR Symposium, you have systematically investigated every correlation that appeared at that time to be emerging, and found most of them untrue: The WR spectra are no longer pure emission spectra (Conti et al., 1979); the WN sequence is not a simple sequence of ionisation (Leep, this symposium, session I, henceforward referred to by session number only) or of H abundance (Willis, II; Perry & Conti, II) or of mass loss rate (Barlow; Hogg; Abbott et al., III). The Of, WN and WC stars are no longer discrete classes but are bridged by intermediate types (Conti, I; Willis and Stickland, VI; Williams, IV) and there are now WO stars (Hummer & Barlow, I & V) and supermassive stars (Cassinelli et al., V) as well. The Ring Nebulae are no longer around only strong-line, single WN stars, but are found around any type of WN star, WC stars and binaries (Heckathorn et al.; Chu; Lortet et al., VI). At best, I can hope to highlight a few things about which the majority of us will agree and to point out a few contradictions.