We review direct and indirect methods to derive metallicity through infrared spectroscopy of massive stars. The choice of different spectral types to obtain abundances allows to trace metallicity for a wide range of ages of the cluster hosting the massive stars. These methods have a great potential to understand the evolution of large amount of heavily obscured galactic clusters, which are currently being discovered through infrared surveys.

During the GA the Task Force for the Preservation and Digitization of Photographic Plates (PDPP) held an open two-session meeting, during which a formal merger between the WG-AC/CdC (Commission 8) and the TF-PDPP was confirmed. A dominant fraction of the members already belonged to both groups, and the nature of the merger is such that the activities of the WG-AC/CdC are now performed by the TF-PDPP.

The standard theory of radiation driven winds has provided a useful framework to understand stellar winds arising from massive stars (O stars, Wolf-Rayet stars, and luminous blue variables). However, with new diagnostics, and advances in spectral modeling, deficiencies in our understanding of stellar winds have been thrust to the forefront of our research efforts. Spectroscopic observations and analyses have shown the importance of inhomogeneities in stellar winds, and revealed that there are fundamental discrepancies between predicted and theoretical mass-loss rates. For late O stars, spectroscopic analyses derive mass-loss rates significantly lower than predicted. For all O stars, observed X-ray fluxes are difficult to reproduce using standard shock theory, while observed X-ray profiles indicate lower mass-loss rates, the potential importance of porosity effects, and an origin surprisingly close to the stellar photosphere. In O stars with weak winds, X-rays play a crucial role in determining the ionization balance, and must be taken into account.

During the course of their evolution, massive stars lose a substantial fraction of their initial mass, both through steady winds and through relatively brief eruptions during their Luminous Blue Variable (LBV) phase. This talk reviews the dynamical driving of this mass loss, contrasting the line-driving of steady winds to the potential role of continuum driving for eruptions during LBV episodes when the star exceeds the Eddington limit. A key theme is to emphasize the inherent limits that self-shadowing places on line-driven mass loss rates, whereas continuum driving can in principle drive mass up to the “photon-tiring” limit, for which the energy to lift the wind becomes equal to the stellar luminosity. We review how the “porosity” of a highly clumped atmosphere can regulate continuum-driven mass loss, but also discuss recent time-dependent simulations of how base mass flux that exceeds the tiring limit can lead to flow stagnation and a complex, time-dependent combination of inflow and outflow regions. A general result is thus that porosity-mediated continuum driving in super-Eddington phases can explain the large, near tiring-limit mass loss inferred for LBV giant eruptions.

Unfortunately the Business Meeting clashed with interesting sessions on stellar convection theory that were very relevant to most members of this Working Group. Hence the attendance was very small, and some preliminary discussions were later followed up by email among the Organising Committee members.

The Business Meeting of Commission 45 was held on 16 August 2006. It was attended by the president and vice-president of the Commission as well as by twenty other members of the Commission. Attendance was limited, as usual, by the unavoidable occurrence of parallel sessions.

The president of the Commission welcomed the participants in the business meeting and provided an overview of the activities carried out during the past triennium 2002-2005. A good number of meetings have been held during this period on close binaries, about two per year, including both classical and interacting systems. One specific Symposium at the General Assembly in Prague, devoted to binary stars as astrophysical tools, showed the vitality of the field and the trend of cooperation between scientists studying close binaries and those specialized in visual double stars. The study of very low-mass binaries, including those containing planet-sized components also received much attention as well as the analysis of massive objects in nearby galaxies.

The meeting was attended by six from the WG (K. Aksnes, J. Blunck, G. Consolmagno, B. Marsden, R. Schulz, V. Shevchenko) and two from the Task Groups (D. Morrison, J. Watanabe). Also the incoming WG members E. Bowell and R. Courtin, as well as some guests, attended.

Applications have been received from Dr. Peter Wheatley (proposed by UK), Prof. Harald Schuh (proposed by Austria), and Dr. Busaba Kramer (proposed by Thailand). All applications were endorsed, with the caveat that Dr. Kramer's application needs to be endorsed by at least one of the other commissions since she has not a publication record in our field.

The president welcomed all the participants of the Business Meeting and remarked that several of the major ongoing and planned Radial Velocity projects were well represented.

The current content of the database was presented, emphasising the substantial progress accomplished since the IAU XXIV General Assembly in Manchester, 2000. More than 1 200 stellar systems have been added to the 8th Catalogue over the past six years, for a total of 540 papers compiled. A first paper was published to make the community aware of this facility (Pourbaix et al. 2004).

Seismic estimates of core overshoot have been derived from extensive high-precision photometric and spectroscopic ground-based (multisite) campaigns for five main-sequence B-type stars. For three of these, the ratio of the near-core rotation frequency to the surface rotation frequency could be estimated as well, from the identified oscillation modes. We summarise these seismic results obtained for B stars. Now that the technique of asteroseismology was proven to work for probing the interior of massive stars, we expect a drastic increase in the precision of the structure parameters from the space missions CoRoT and Kepler, as well as from currently ongoing ground-based campaigns, in the coming years.

The current Statutes and Bye-Laws were extensively re-written and approved at the Sydney GA in 2003 in order to streamline many of the processes of the IAU and to bring the IAU more into conformity with the structure of other ICSU unions. These revision have generally been well received, however there have been several changes to the Statutes and Bye-Laws that Individual Members and National Members have deemed desirable in the past three years and which have been brought to the attention of the EC.

Young O stars are strong, hard, and variable X-ray sources; properties that strongly affect their circumstellar and galactic environments. After ≈ 1 Myr, these stars settle down to become steady sources of soft X-rays. I will use high-resolution X-ray spectroscopy and MHD modeling to show that young O stars like θ1 Ori C are well explained by the magnetically channeled wind shock scenario. After their magnetic fields dissipate, older O stars produce X-rays via shock heating in their unstable stellar winds. Here too I will use X-ray spectroscopy and numerical modeling to confirm this scenario. In addition to elucidating the nature and cause of the O star X-ray emission, modeling of the high-resolution X-ray spectra of O supergiants provides strong evidence that mass-loss rates of these O stars have been overestimated.

The programme International Schools for Young Astronomers, hereafter named ISYA, is organized by IAU COMMISSION 46 on Astronomy Education & Development since 1967. We present here a brief history of the development of this programme since its creation till 2006. Much more data can be found in the Transactions of the IAU, either Vol. A or B, as well as in two papers published in proceedings of meetings; the references of these publications are given at the end of this report.

Red supergiants (RSGs) are an evolved stage in the life of intermediate massive stars (≤ 25 M⊙). For many years, their location in the H-R diagram was at variance with the evolutionary models. Using the MARCS stellar atmospheres, we have determined new effective temperatures and bolometric luminosities for RSGs in the Milky Way, LMC, and SMC, and our work has resulted in much better agreement with the evolutionary models. We have also found evidence of significant visual extinction due to circumstellar dust. Although in the Milky Way the RSGs contribute only a small fraction (< 1%) of the dust to the interstellar medium (ISM), in starburst galaxies or galaxies at large look-back times, we expect that RSGs may be the main dust source. We are in the process of extending this work now to RSGs of higher and lower metallicities using the galaxies M31 and WLM.

The evolved cool stars near the empirical upper luminosity boundary in the HR Diagram all show evidence for considerable instability perhaps due to their proximity to this stability limit and/or their evolutionary state. Recent high resolution imaging and spectroscopy of several of these stars have revealed a subset characterized by complex ejecta and evidence for episodic mass loss driven by convective activity and magnetic fields. This group includes famous stars such as the red supergiants VY CMa, NML Cyg and the post RSG IRC +10420. I will review the observational evidence and discuss the implications for the final stages of these evolved stars, their mass loss mechanism, and evolutionary state.

In our commission the vice-president (VP) becomes the president, and a new VP is chosen from members of the Organizing Committee. The position of secretary was discontinued and its responsibilities incorporated into the VP position. The president announced that the new officers are Steven R. Federman (president) and Glenn M. Wahlgren (vice-president).