We start by looking at some recent developments in field measurements in middle main sequence and pre-main sequence stars. Then we consider how other magnetic effects such as the Hanle effect and continuum polarisation may be used to detect fields in a variety of stellar environments such as the solar corona and white dwarf atmospheres. Finally we consider how the current body of observational knowledge about magnetic stars may be integrated into a roughly coherent, provisional scenario of field origin and evolution.

We discuss our ideas how to make best use of the Antarctica Dome Csite equipped with a 2.4 m infrared telescope (“Hubble on the ground”),including day time observations of the Magellanic Clouds in the 3 monthsAntarctic Summer.

Site testing data provides an essential part of the justification for funding any new astronomical facility by defining the technological design and determining the telescope performance, thus allowing the scientific objectives to be prioritised. Here we review the current status of site testing at Dome C by examining the range of instruments that have been, or are planned to be, deployed to the site. We then investigate in more detail preliminary data which has so far proven crucial for telescope design, data for which discrepancies exist between two or more instruments, and required data for which there are no current plans to obtain. We discuss the implications of this data on the technical design, expected performance, and the scientific capabilities for a 2.5 m class optical/infrared telescope. Finally, we identify the site parameters that require further study, and define the experiments necessary to determine these parameters.

We describe a prototype instrument built to validate the principleof the dispersed speckle method (Borkowski et al. 2002;Borkowski et al. 2004). This prototype, still under test, is aspectrograph where the multiple pupil, highly reduced in size,replaces the slit. An array of optical wedges is added near thegrating to separate the spectra from each speckle. Thefabrication and properties will be explained.

This review presents basic equations for the solution of the NLTE radiative transferproblem for trace elements and methods for its solution are summarized. The importance offrequency coupling in radiative transfer in stellar atmospheres is emphasized.

We present new results of a long-term investigation of the stellar content of the Large and the Small Magellanic Cloud. The main aim of the project is to obtain a comprehensive knowledge of the star formation history of these two nearby galaxies. Here we discuss the latest findings obtained using new data and a variety of different observational approaches, based on wide-field ground-based photometry and low-resolution CaT spectra. We find evidence of two main star formation events across the LMC disk. We also found evidence that the young and intermediate age population (<5 Gyr) presents a steeper gradient with radius than the old one (>8 Gyr). In particular, the young (<2 Gyr) component seems to extend to 8 degrees from the center, distance at which it decreases abruptly. At larger distance, the old population dominates, extending to at least 13.5 kpc. We also report the discovery of a population of stars located across the Magellanic Bridge, compatible with the old population of the LMC.

Detection of a composite flux in Gaia photometry can serve as an indication of aphotometrically unresolved binarity and can allow us to contribute to the parameterizationof the components of binary systems. A main goal of the present study is to develop amethod of automatic photometric detection, based on theoretical stellar spectral energydistributions and general understanding of binary evolution.

The following procedure is applied to achieve the declared goal. One can compose possiblepairs of components, based on evolution concept, and using theoretical binary evolutionarytracks. This can be done for all stages of binary evolution, excluding perhaps the mostmarginal and rapid stages. Theoretical spectrophotometric spectral energy distributionsand response functions of Gaia photometric bands allows us to compute colour-indices ofsuch pairs, when they are unresolved, as well as of single stars. Usage of an interstellarextinction law gives us theoretical colour-indices of reddened objects, both single starsand unresolved binaries. When plotted on a multidimensional Gaia colour space, they allowus to indicate areas, where unresolved binaries can be easily separated from single stars.The procedure also indicates Gaia colour indices, suitable to distinguish those pairs fromsingle stars.

As an output of the procedure, a Gaia list of detected photometrically unresolvedbinaries with physical parameters can be compiled.

The standard model of cosmology suggests the existence of two components, “dark matter” and “dark energy”, which determine the fate of the Universe. Their nature is still under investigation, and no direct proof of their existences has emerged yet. There exist alternative models which reinterpret the cosmological observations, for example by replacing the dark energy/dark matter hypothesis by the existence of a unique dark component, the dark fluid, which is able to mimic the behaviour of both components. After a quick review of the cosmological constraints on this unifying dark fluid, we will present a model of dark fluid based on a complex scalar field and discuss the problem of the choice of the potential.

This paper describes a coronagraphic nulling interferometer calledKEOPS (Kiloparsec Explorer for Optical Planet Search) to be placedon the Dome C plateau of Antarctica. KEOPS is an interferometricarray of 39 1 m–2 m telescopes spread over kilometric baselines andoperated in the thermal IR region. It could search and characterizeall potential exoEarths within the 1 kpc diameter region observablefrom Dome C. We argue that even in the very difficult operationconditions of Antarctica, such a facility can compete at a muchlower cost with the non-zero risk space missions, both for for ExPNssearch and their spectroscopic characterization plus sub-massnap-shot imaging of galactic and extra-galactic compact sources.

Hereafter we give a brief history of our contribution to astronomical site testing in Antarctica, at least for thehigh angular resolution in the visible range. The decision to undertake the first site testing at South Pole began one year after a congress organized by French Académie des Sciences, in year 1992. Indeed, in 1993 a meeting took place in Chicagowith the participation of Peter Gillingham, Al Harper and Jean Vernin where each one took the respectiveresponsibility of 1) giving a PhD student, 2) the South Pole infrastructure and 3) the relevant instruments.During winter 1995, thanks to a mast equipped with micro-thermal sensors, we demonstrated (Marks et al., 1996, A&AS, 118, 1)that the first 30 m of the surface layer was disrupted by strong optical turbulence. Then, the year after,15 balloons equipped with micro-thermal probes were successfully launched from South Pole. Marks et al. (1999, A&AS, 134, 161)shown that most of the optical turbulence at South Pole was concentrated within a layer 200 m thick abovethe ice level.From this study, it becomes clear that the noticeable katabatic wind present at South Pole was generatingthis huge surface layer and that is why we oriented our astronomical site characterization towardDôme C.
Our first summer seeing estimations began in 2000, which demonstrated (Aristidi et al., 2003, A&AS, 406, L19 & Aristidi et al., 2005, A&A, 444, 651)that, as expected, the surface wind was much less than at South Pole, and, as a matter of fact, the seeingwas much better, and was even exceptional during the four hours of the afternoon where a seeing of less than 0.5 arcsec was measured. In 2005, the Concordia base was first open during the polar night, and one of us,A. Agabi was able to launch 41 balloons equipped with micro-thermal sensors. A differential image motionmonitor (DIMM) was also setup with success. At mid winter, Agabi et al. (2006, PASP, 118, 344) showed that mostof the optical turbulence came from the first 30 m surface layer and very little from the rest of theatmosphere (1.3 arcsec above 8.5 m and 0.37 arcsec above 30 m).

For more than ten years, a collaboration of European scientists has been producingsimulations of the Gaia mission. These simulations range from detailed realistic simulatedCCD images to large volume simulations of the Gaia telemetry.

The data of this decade of simulations has been used for many purposes: instrumentdesign, data processing software testing and validation, prediction of missionperformances, etc. Today the launch date is getting closer and the task of the simulatorin the mission preparation will be wrapped up in a couple of years.

However, this is not the end of the story since the Gaia simulator can also be used forthe preparation of the scientific exploitation of the Gaia data. In this talk we willpresent the simulator and its components, the data it can produce and the perspectives forthe utilisation of this data during the mission, both for data evaluation and scientificexploitation.

More than 100 reactions between stable molecules and free radicals have been shown to remain rapid at low temperatures. In contrast, reactions between two unstable radicals have received much less attention due to the added complexity of producing and measuring excess radical concentrations. We performed kinetic experiments on the barrierless N + OH and N + CN reactions in a supersonic flow (Laval nozzle) reactor. The results provide insight into the gas-phase formation mechanisms of molecular nitrogen in interstellar clouds (ISCs).

We present a new multi–fluid, grid MHD code PIERNIK, which is based on the Relaxing TVD scheme (Jin & Xin 1995). The original scheme (see Trac & Pen 2003; Pen 2003) has been extended by an addition of dynamically independent, but interacting fluids: dust and a diffusive cosmic ray gas, described within the fluid approximation, with an option to add other fluids in an easy way. The code has been equipped with shearing–box boundary conditions, and a selfgravity module, Ohmic resistivity module, as well as other facilities which are useful in astrophysical fluid–dynamical simulations. The code is parallelized by means of the MPI library. In this paper we present an extension of PIERNIK, which is designed for simulations of diffusive propagation of the Cosmic–Ray (CR) component in the magnetized ISM.

I review recent results on the angular distribution of substructure in CDM halos. I show that the subhalo distribution isanisotropic and generally prolate with a long axis that is closely aligned with the long axis of the total mass distribution of the host halo. I show that the correlation between the subhalo distribution and the long axis of the host halo is strong both in dissipationless and dissipational gasdynamical simulations. More massive subhalos tend to be more strongly clustered along the major axis of the host halo reflecting filamentary accretion. The anisotropy of subhalos has potential implications for the interpretation of several observations. For example, I show that while the mean projected mass fraction in substructure in the central regions of CDM halos is fsub ≈ 0.4%, fsub is a strong function of projection angle and is ~6 times higher for projections nearly collinear with the major axis of the host.

This paper presents the use of marked point processes for studying the galaxy distribution in our Universe. The methodology we propose has a general character and it is based on the following tools: summary statistics, stochastic modelling, simulation algorithms and statistical applications.

Inclusion compounds made of a water ice network, clathrate hydrates, are investigated by infrared spectroscopy. Because they can trap important “guest” volatiles species, they may influence the equilibrium, exchange and flux of volatiles in many bodies of the solar system. Their spectroscopic behaviour at low temperature (10–200 K) are shown and the search for their signatures by comparison to solar system objects remote spectra are discussed.

Many are the proposed scenarios for the formation of the thick disk of the Milky Way,going from the merger with smaller galaxies to fast gas accretion in the early Universe.Crucial information on which was the dominant mechanism for the formation of the thickdisk and other Galactic components is encoded in the chemical properties of their stars.By comparing the chemical properties of bulge, thick and thin disk stars one can addressthe question of which, among the competing processes of dissipation, satellite accretionand radial migration, play the dominant role in the formation of the different Galacticcomponents. The main difficulty at present is that current data samples suffer fromselection biases. Gaia shall bring a quantum leap to the solution of this problem, byproviding fiducial samples of the different galactic components with both, chemical andfull kinematic information. To pave the road for Gaia, theoretical models need to beimproved by taking into account both chemistry and dynamical aspects. A work of this kindis underway in Geneva Observatory.

By construction, optical (and near-infrared) interferometers typically have resolutions designed to resolve stellar and circumstellar features. Therefore gaging the point-source response of the interferometer in its operating environment is critical to the scientific interpretation of data from these devices. This is typically performed with observations of calibration sources that are modeled to be simple and quasi-unresolved by the interferometer. Herein I will discuss the goals and strategies for and issues with the selection of objects to serve as calibration sources for optical interferometry visibility measurements.