We report on the spectroscopic observation of a new Wolf-Rayet star not already identified. This star is located in our Galaxy, in the Canis Majoris region and was found during a southern spectroscopic survey of stars previously identified as Hα emission objects. The star, SPH 2, after Schwartz, Persson & Hamann (1990), shows the main characteristics of a WN star and a strong C IV 5808 Å emission line typical of a WC star.

We are motivated to study the Ne/He abundance ratio at the surfaces of Wolf-Rayet stars by evolutionary models, which have predicted enhancements by more than an order of magnitude over cosmic levels during the WC stage (e.g., Maeder 1991). This should occur early in the WC phase, as core-hydrogen is exhausted and the CNO bi-cycle gives way to the following chain of reactions for the Galactic stars:

The latest evolutionary models, which include the effects of interior mixing due to stellar rotation, indicate that the enhancement may be somewhat more gradual, but that the Ne/He ratio is essentially unchanged in its peak value, coinciding with complete H-depletion (e.g., Meynet, these Proceedings).

The NEWSIPS-reprocessing of IUE data permits the extraction of spectra to wavelengths as short as 1150 Å. We present representative well-exposed IUE spectra of Wolf-Rayet stars covering the 1150–1220 Å region with a resolution of 0.1 Å. The C III 1175 Å line in WC and some WN stars typically shows a P-Cygni profile, with dacs apparent in time series spectra. Superimposed on the stellar spectra are many strong interstellar absorption lines of N I, Si II and other species. These spectra are a guide to a portion of the wavelength region to be covered by FUSE, and an indication of the new information that will be available in the far-UV range with FUSE.

We present first results of our search for Wolf-Rayet members of OB associations, aiming in determination of distances and absolute magnitudes for WR stars.

Clumping-corrected mass-loss rates of Wolf-Rayet stars lie in the range 0.2–10 x 10−5 M⊙ yr−1. It was found that optically thick wind models can lead to the observed mass-loss rates of WR stars at certain energy supply conditions in the subsonic zone.

Here we present fundamental parameters (masses, spectral classifications, rotational velocities) obtained from a combination of spectroscopic and photometric orbital solutions for the O-type binary systems HD 152248, HD 149404, and HD 135240. We also present estimated masses derived from theoretical single star evolutionary tracks for these same stars. In all cases the evolutionary masses are larger than those derived from observations.

The Wolf-Rayet WO spectral sequence was introduced by Barlow & Hummer (1982) for four Pop I WR stars with very strong O VI 381 nm doublet emission. At the time, the evolution of very massive stars was poorly known, and their classification was based on phenomenological grounds. Recently, efforts to improve the WO spectral subtype classification are increasing (Kingsburgh et al. 1995; Crowther et al. 1998).

Although substantial progress has been achieved since the discovery of X-ray emission from early-type stars with the EINSTEIN satellite, several crucial aspects of this phenomenon are still not fully understood. Considerable breakthroughs in this field are expected from observations with the X-ray Multi-Mirror satellite (XMM) due for launch in early 2000. XMM is the second cornerstone mission of the ESA Horizon 2000 science programme (see Lumb et al. 1996 and references therein for an overall description of the satellite). XMM offers a large effective area over a wide range of energies and its instrumentation provides simultaneously non-dispersive spectroscopic imaging (EPIC - European Photon Imaging Camera), medium-resolution dispersive spectroscopy (RGS - Reflection Grating Spectrometer) and optical-UV imaging (OM - Optical Monitor).

We summarize an analysis of low-resolution IUE archival data for galactic and LMC Wolf-Rayet stars. We examine the correlation between ionization potential with line-width (FWHM) constituting a sample of stars showing a well-defined UV ionization structure.

In the present paper, we discuss photometric observations of the February 1996 eclipse of the very massive WR+O binary WR 22. Our data were obtained with a set of narrow-band filters, specially designed for the study of WR stars.

We use ISO-PHOT maps around five WN stars to derive their far-infrared fluxes. In some cases we also detect a nebula around the star.

We are investigating two long-period WR+O binaries, γ2 Velorum (WC8+O7.5, P = 78.5d) and WR 22 (WN7+abs+O, P = 80.3 d). We derive new orbital elements for both binaries and we give preliminary results of our analysis of the expansion velocity and ionization structure of γ2 Vel.

We present the temporal variation of the stellar parameters of the erupting star in HD 5980. We derive the effective temperature and radius from the observed changes of the visual magnitude. Our analysis is based on the assumption that the luminosity of the erupting star remained constant and that the brightness of the second star did not vary.

We present a deep look into the Cygnus OB2 region using the WSRT. A 2° x 2° map of the optically highly-obscured region was obtained at 1400 MHz, with a noise level down to 0.2 mJy and an angular resolution of 1″. We will compare the resulting radio point source list with optical and near-IR catalogues, in order to identify stellar wind sources like WR and OB stars.

We have completed a direct narrow-band/broad-band Schmidt-plate survey of large areas of the southern Milky Way for new Wolf-Rayet stars as faint as 19th b magnitude. The 31 newly detected stars in the completed survey are amongst the reddest and/or most distant known in the Galaxy. We have obtained spectra of all candidate WR stars in the 22 fields stretching from l = 282° to l = 341° in longitude, and Δb = 3.5° in latitude, covering about 180 square degrees. We also observed two isolated Milky Way fields centered at l = 0° and l = 8°. Eighteen new WR stars are reported here for the first time. Combined with the 13 new WR stars we have already reported in Carina, our list of 31 new Galactic WR stars reaches 3–4 magnitudes fainter than previous surveys. Thirteen of the 18 new WR stars reported here are of subtype WN, while five are of subtype WC. Our new WR stars clearly demonstrate an increasing WN/WC number ratio with increasing Galactocentric distance.

We present the results of observations of a sample of Galactic WR stars with SCORE, the SIRTF Cornell Echelle spectrograph. Spectra with resolution R ≃ 600 and wavelength coverage from 7.5–15 μm were obtained for a variety of WR subtypes.

After a quarter century of dreams and designs, the Space Infrared Telescope Facility (SIRTF) has begun formal development, with a planned launch date of December 2001. SIRTF consists of a 85 cm telescope and three cryogenically-cooled science instruments capable of performing imaging, photometry, and spectroscopy in the 3–180 μm wavelength range. Incorporating the latest in large-format infrared detector arrays, SIRTF offers orders-of-magnitude improvements in capability over existing programs. One of the many innovative aspects of this observatory is the Legacy Science program, in which hundreds, perhaps thousands of hours of observing time will be allocated to coherent groups of scientists to carry out programs whose scientific data, upon archiving, are of general and lasting importance to the broad community. The capabilities of this telesope, and the possibiltiy of participating in a Legacy Science proposal, offer the community of hot stellar astronomers an unprecedented scientific opportunity.

Spectroscopy of the individual stellar components in four compact OB multiple systems of the LMC, previously imaged with the HST-WFPCS, has been performed with the HST-FOS. In every case, the uncontaminated spectra of the WR and/or Of-type components have been observed for the first time. The spectra of the normal OB companions provide information about the initial masses and ages of the peculiar objects. Several additional evolved and peculiar objects within these systems have also been discovered.

We present preliminary results of our HST-WFPC2 pc-survey of Wolf-Rayet stars. Initiated in 1996, the goal was to discover new companions to, and cluster/association memberships of, known Galactic WR stars. From these results, Niemela et al. (1998) have already established a firm link between non-thermal radio emission and the location of binary wind-collision zones for WR 146 (confirming radio data of Dougherty et al. 1996) and WR 147 (confirming radio and IR data of Williams et al. 1997; see also Williams, these Proceedings), and confirmed the presence of a binary companion for WR 86 (listed by Jeffers et al. 1963). Here, for the first time, we present new information on WR38, WR38a, and WR 104.

We have updated the list of promising candidates for observations of non-thermal high-energy emission from Galactic Wolf-Rayet stars with present and future X/γ-ray instruments.