We present the evolution of helium stars in binary systems with a 1.4 M⊙ neutron-star companion which will produce double neutron-star binaries, i.e., systems with helium stars more massive than 2.5 M⊙. We found that mass transfer from helium star less massive than ~ 3.3 M⊙ will end up in a common-envelope phase. If the neutron star has enough time to complete the spiral-in before the core of the helium star collapses, the system will become a very tight double neutron-star binary (P ≈ 0d.01). More massive helium stars do not go through a dynamically-unstable mass transfer. The outcome of binaries with helium star in this range of mass is double-neutron star systems with period of 0d.1-1d, suggesting them to be the progenitor of the observed Galactic double neutron-star pulsars B 1913+16 and B 15344+12. Wide DNS pulsars like J 1518+4904 are produced from helium star-neutron star binaries which avoid Roche-lobe overflow. We are also able to distinguish the progenitors of Type Ib supernovae (as the high-mass helium stars or systems in wide orbits) from those of Type Ic supernovae (as the lower-mass helium stars or systems in close orbits).

Mass loss due to outflow is one factor introducing uncertainty into our understanding of the evolution of massive stars. There is a need of a theory, that would make it possible to take into account mass loss in the process of evolutionary computations in a self-consistent way. It is currently clear that the role of outflow is extremely important for stellar evolution, but quantitative conclusions about mass-loss rates remain uncertain. The evolution of stars with masses M ≥ 15 M⊙ is accompanied by mass loss at rates reaching 10–4-10–6 M⊙ yr–1. This strongly influences the evolution of such stars in the supergiant stage.

One of the best tracers of massive stars is the rate of supernovae in galaxies. Studies of the supernova rate in galaxies are though severely affected by the line of sight extinction. Geometrical effects (e.g., edgewise presentation) may lead to the majority of supernovae that appear in a galaxy being undetectable in the visible. We propose to use canaricam on the Spanish 10m Gran Telescopio Canarias to measure the true supernova rate in a sample of galaxies, independent of extinction and line of sight effects, by measuring at 10 μm where the extinction is almost negligible. This system allows Type Ia SNe to be detected out to 100 Mpc in 120 s of integration, thus 360 galaxies per year for which we are sensitive to SNe can be covered per hour of telescope time per month.

We have calculated detailed, fully non-LTE, model atomospheres for massive zero-metal stars. We find the atmospheres of massive primordial stars become unbound due to radiation pressure on lines and continua over a much larger fraction of their evolution than previously expected.

We identify two possible paths for the progenitor evolution of observed WNE+O binaries with WNE/O mass ratios close to 0.5 and periods between 7 and 10 d. We show, through detailed binary evolution models, that with the assumption that the O-type star expels most of the matter flowing at it during mass transfer, one possibility to obtain the observed systems is through Case A mass transfer. We find a second solution using standard common envelope evolution. We conclude that in either case the O-type star in the three investigated systems did not accrete significant amounts of mass. We discuss the intricate situation that in other cases massive close binaries may evolve conservatively.

We present very preliminary results of a spectroscopic survey of all known 47 WNL stars in the LMC.

A novel project to directly detect the progenitor stars of nearby core-collapse supernovae in pre-discovery archive images is briefly described.

The 1032, 1038 Å emission lines of O vi were detected from SN 1987A by the FUSE satellite observations in 2000 and 2001. The lines are extremely narrow (fwhm < 35kms–1), indicating that the emission is not a by-product of the various circums tellar shock phenomena. The most likely origin of the O vi emission lines is recombination of the SN progenitor's red giant wind that was photoionized by the SN shock breakout on 1987 Feb 23.

The principal role of strong horizontal diffusion in overcoming the inhibiting effect of mean molecular weight gradient and in producing partial matter mixing between convective core and radiative envelope of a rotating star, is shown.

The determination of the external galaxies morphology is generally based on their appearance on optical images. At these wavelengths young stellar population and their associated H ii regions, which can be grouped into star-forming complexes, appear preferentially located along spiral arms. Hence, it is naturally to use the same tracers to delineate the arms of our own Galaxy. But, where for external galaxies the distribution of star-forming complexes along the spiral arms is generally evident from direct imaging, for our Galaxy the spiral arms are strung out along the line of sight, leading to the superposition and mixing of information from the different complexes in the spiral arms making it difficult to distinguish them. Thus to access to the spatial distribution of young objects, hence to the large scale structure of our Galaxy, it is required first to identify and collect star-forming complexes (molecular clouds – H ii regions – OB stars) and then to determine their distance. In this framework I review the observational results and difficulties concerning the distribution of star-forming complexes and the determination of the structure of our Galaxy.

The recent VIIth Catalogue of Galactic Wolf-Rayet Stars (van der Hucht 2001), lists 227 Population I WR stars, comprising 127 WN, 87 WC, 10 WN/WC and 3 WO stars. Additional discoveries since then bring the census to ≳ 253 WR stars, including ≳ 27 WNL and 13 WCL stars within 50 pc of the Galactic Center. A re-determination of the optical photometric distances and the galactic distribution of WR stars shows in the solar neighbourhood (d < 3 kpc) a projected surface density of 2.7 WR stars per kpc2, a NWC/NWN number ratio of 1.3, and a WR binary frequency of 40%. Compared with other Local Group galaxies, the NWC/NWN number ratio in the solar neighborhood is a factor ~2 above the observed metallicity-dependent trend. This could imply that some 30 galactic WN stars in the d < 3 kpc volume are still hiding. Preliminary results of infrared photometric distance determinations are shown. The galactocentric distance (RWR) distribution per subtype shows RWN and RWC decreasing with later WN and WC subtypes. The observed trend is more indicative of WNE → WCE and WNL → WCL subtype evolution than of WNL → WNE and WCL → WCE subtype evolution.

I describe recent spectroscopic observations of Wolf-Rayet stars in three giant H ii regions of M 33 and in the Local Group starburst galaxy IC 10.

Current research using near-infrared techniques for investigating stellar populations in massive Galactic star clusters is reviewed. In particular, I discuss in some detail a survey of obscured Galactic Giant H ii (GH ii) regions and the associated stellar clusters embedded in them. The regions have been selected as the most luminous radio continuum sources. This selection criteria has the consequence that the observed clusters are among the youngest massive star clusters in the Galaxy. The emergent stellar populations are further studied through near-infrared spectroscopy of the brighter members, a number of which are young stellar objects with signatures of dense circumstellar material which might arise from in or out-flows, or in disks. New results from 8m class telescopes employing velocity resolved near-infrared spectroscopy and high angular resolution mid-infrared imaging hold great promise for future detailed investigations.

Near-infrared, spectroscopic studies of central ionizing sources of very young H ii regions is presented in conjunction with a recently available, sophisticated atmospheric code to constrain the physical conditions and environment of very massive stars at very early stages of evolution. Combining high quality near-infrared spectroscopy of very young massive stars with model atmosphere calculations should allow for the most accurate quantitative determination of Teff, rotation, L, and log g, and to search for binaries and possible disk or in-fall signatures in forming or recently formed massive stars. These characteristics make up a vital boundary condition constraining theories on massive star formation.

In recent years, a number of extragalactic massive stars clusters have been detected which are still deeply embedded in their birth material In many cases, these clusters are only visible in the mid-IR to radio regimes, and have typically been detected as ‘inverted’ spectrum radio sources. These clusters appear to have properties which are analogous to those of ultracompact H ii (UCH ii) regions in the Galaxy, albeit vastly scaled up in total mass and luminosity. The ultra-young clusters appear to form with a continuum of masses, and the most massive are consistent with being the progenitors of globular clusters. Here I will overview the properties of the currently known sample of ultradense H ii (UDH ii) regions and examine their relation to Galactic UCH ii regions.

The ionization structure of nebulae depends on the spectral energy distribution of the ionizing stars. Therefore nebulae are potential tools to check the validity of the energy distribution predicted by stellar atmosphere models. However, the problem is complicated by the fact that the ionization structure also depends on the nebular density distribution and that the predictions of photo-ionization models strongly rely on atomic physics computations, which bear their own uncertainties.

Our Galactic Center hosts over 10% of the known massive stars in the Galaxy. The majority of these stars are located in three particularly massive clusters that formed within the past 5 Myr. While these clusters are extraordinary, their formation repesents about half of the total inferred star-formation rate in the Galactic Center. There is mounting evidence that the clusters are just present-day examples of the hundreds of such similar clusters that must have been created in the past, and whose stars now comprise the bulk of all stars seen in the region. I discuss the massive stellar content in the Galactic Center and present a new analysis that suggests that effects of continuous star-formation in the Galactic Center can be seen in the observed luminosity functions newly-obtained HST-nicmos and Gemini-ao data.

High-resolution multi-frequency observations made with the VLA have revealed the presence of stellar winds in two of the three known massive stellar clusters at the Galactic Center (GC). At a distance of only 8.0 kpc, we are able to resolve radio sources associated with individual near-infrared sources known to be losing mass at high rates. Herein, I discuss the spectral and spatial properties of the radio sources and their near-infrared counterparts, their inferred mass-loss rates, variability and the prospects for detecting stellar winds sources in the Central Cluster, near the supermassive blackhole SgrA*. Such massive clusters as these three GC clusters have a profound impact on the interstellar medium, as evidenced by radio and X-ray observations of the surrounding regions.

The Cygnus X region is one of the most nearby star formation regions within our Galaxy, that is recognised by prominent emission throughout the entire electromagnetic spectrum, from radio to gamma-ray waves. The centre is populated by the peculiar stellar cluster Cyg OB2, traditionally classified as OB association, but in the light of modern data more likely the prototype of a young globular cluster within our own Galaxy. Heavily shredded by dense molecular clouds this object has been less thoroughly studied than other, more distant star formation complexes in the Milky Way. I will review our current knowledge about this object, by exposing its properties and that of its environment throughout the entire electromagnetic spectrum. Particular emphasis will be given to infrared, radio-continuum, X-ray, and gamma-ray line observations that find in Cyg OB2 a text-book case for multiwavelength studies.

While NGC 3603 is often quoted as the most massive visible Giant H ii Region in the Galaxy, there are other similar and even more massive regions now being found towards the inner Galaxy in the near-IR. Nevertheless, NGC 3603 still retains the status of clone to the dense core-object in 30 Dor, R 136 — but 7x closer and 49x less crowded! This paper summarizes the most recent findings concerning NGC 3603's color-magnitude diagram (CMD), initial mass function (IMF), mass segregation and stellar content — including its unusually luminous H-rich WNL members — down to its pre-main-sequence stars near the H-burning limit. Of special relevance are new high-resolution X-ray and radio images as related to merging/colliding winds and three massive proplyd-like objects. NGC 3603 is a somewhat younger, hotter, scaled-down version of typical starbursts found in other galaxies.