Results are presented from studies of the process of plasma acceleration along the current sheet width under different experimental conditions. The behavior of the neutral component is included in the analysis.

We characterize PAH populations in 22 metal-poor blue compact dwarf galaxies (BCDs), 16of which have an oxygen abundance 12+log(O/H) ≲ 8. This is the largest sample ever studiedat such low metallicities. The relative PAH intensities of the 6.2, 7.7, 8.6 and11.3 μm features in these BCDs suggest a deficit of small PAH carriers,or alternatively, an excess of large ones at these low abundances.

We show the power of the method of the color indices that uses the commonly availablemultiband photometry of optical afterglows (OAs) of long GRBs detected bySwift. Our study shows that for most OAs, in the observer frame, thesecolors, corrected for the Galactic reddening, display prominent clustering in thecolor-color diagrams. The color indices enable us to distinguish OAs from other types ofobjects even without available gamma-ray emission. The color-color diagrams can be used toassess the extinction inside the host galaxy. Our approach is also generally important forinvestigating the numerous faint OAs for which obtaining spectra with good S/N ratio isoften impossible.

Owing to its wide sky coverage and broad energy range, the FermiGamma-ray Burst Monitor (GBM) is an excellent observer of the transient hardX-ray sky. GBM detects about 240 triggered Gamma-Ray Bursts (GRBs) per year, includingover 30 which also trigger the Swift Burst Alert Telescope (BAT). Thenumber of GRBs seen in common with Swift is smaller than expected fromthe overlap in sky coverage because GBM is not as sensitive as the BAT and the GBM GRBpopulation is thus skewed to the brighter, closer bursts. This population includes about45 short GRBs per year, giving GBM an excellent opportunity to observe the electromagneticcounterpart to any gravitational wave candidate resulting from the merger of compactbinary members. The same characteristics make GBM an ideal partner for neutrino searchesfrom nearby GRBs, and for the elusive Very-High Energy (VHE) counterparts to GRBs. Withthe deployment of the next-generation gravitational-wave detectors (Advanced LIGO/VIRGO)and VHE experiments (CTA and HAWC) potentially within the lifetime of the FermiGamma-ray Space Telescope, the prospects for breakthrough observations aregood.

The ESTA activity under the CoRoT project aims at testing the tools for computing stellar models and oscillation frequencies that will be used in the analysis of asteroseismic data from CoRoT and other large-scale upcoming asteroseismic projects. Here I report results of comparisons between calculations using the Aarhus code (ASTEC) and two other codes, for models that include diffusion and settling. It is found that there are likely deficiencies, requiring further study, in the ASTEC computation of models including convective cores.

We have expanded our model of photodissociation regions (PDRs) to include the freezing of O- and C-bearing species on dust grains, simple grain surface chemistry, and desorption processes, including photodesorption, that may be important in the surface layers of diffuse, translucent, and dense molecular clouds. The main result of including these processes is that a number of important gas-phase species, including H2O and O2, peak in abundance at AV ~ few into the cloud. Most of the gas-phase column, and most of the emission, from these species arises in the peak. Closer to the surface, H2O and O2 are photodissociated, while deeper into the cloud, they freeze out onto grain surfaces. The result is H2O and O2 column densities that are nearly constant for a wide range of gas densities, n, and for FUV fields G0 $\lesssim$ 500. The roughly constant column densities of these species provides an explanation for the low line-of-sight average abundances of H2O observed toward GMCs. The model results also suggest that regions of high FUV field are the best places to search for O2.

We describe the current, 9-spacecraft Interplanetary Network (IPN). The IPN detects about325 gamma-ray bursts per year, of which about 100 are not localized by any other missions.We give some examples of how the data, which are public, can be utilized.

A report on the current status of the ESTA- Task 2 (oscillation frequencies comparison) is presented. Several types of comparisons have been made using the frequencies provided by different numerical codes. The equilibrium model is the same for all of them, and additionally some requirements such as boundary conditions, no re-meshing, etc, are also imposed. Some unexpected differences appear in the frequency and large separation comparisons. In the high frequency region these differences can be due to the order of the integration scheme used to solve the partial differential equations (or to the lack of number of mesh points in the outer layers). In the region around the fundamental radial mode and the low frequency region, important differences appear for the avoided crossing and the trapped modes respectively, the reason maybe due to the different sensitivity of each code to the profile of the Brunt-Väisälä frequency. The next step will be to test the accuracy of the codes using a model with a larger number of mesh points and with a better described Brunt-Väisälä frequency.

Nonparametric regression is a powerful tool to estimate nonlinear relations between some predictors and a response variable. However, when the number of predictors is high, nonparametric estimators may suffer from the curse of dimensionality. In this chapter, we show how a dimension reduction method (namely Sliced Inverse Regression) can be combined with nonparametric kernel regression to overcome this drawback. The methods are illustrated both on simulated datasets as well as on an astronomy dataset using the R software.

Regarding its seeing properties or its photometric quality aswell, the Dome C Concordia site is presented as being anintermediate solution between space and a good mountainobservatory. This statement still needs somewhat further nighttime confirmation. If really true, as is more and more expectedafter the preliminary site testing campaigns (Aristidi etal. 2004; Storey et al. 2004), thisopens extremely promising prospects for asteroseismology ofsolar-type stars, and also of any kind of star for which acontinuous observation much longer than 12 hours is an importantrequirement.

In this paper we present some preliminary simulations concerning adaptive-optics-aided coronagraphy.The starting point used for this goal is the software system CAOS (Code for Adaptive Optics System),because of the simulation design ease given by its graphical programming environment, and thecompleteness and flexibility of its set of modules dedicated to adaptive optics (AO) simulations.We have so developed the complementary numerical tools necessary to implement the CoronographeInterférentielle Achromatique (CIA) within CAOS, together with differential imaging, andconsidering Fresnel propagation through the turbulent atmosphere. Hence we give an example ofapplication to exoplanet detection with the characteristics of the Very Large Telescope AO systemNAOS and the CIA.Finally, we also discuss on some other recent developments concerning CAOS.

The main characteristics of the average spectrum of radioquiet AGN in the UV and X-ray range are reviewed, and the emissionmechanisms are discussed in the framework of accretion disk models,in particular the "irradiated cold relativistic disk". It is shown thatsome problems arise in confronting the predictions of the model to theobservations. We propose an alternative model in terms of a hot disksurrounded by a cold Compton thick medium. Finally we mentionproblems with remote regions of the accretion disk.

This paper reviews the various population and depopulation mechanisms that establish the statistical equilibrium of atoms and shows how departures from LTE for level occupation numbers translate in non-LTE effects for spectral lines.

Progress in our understanding of solar magnetism and activity rest to a large part on our ability to improve spatial resolutionfor resolving the solar surface magnetic fields fine structure. The solarcorona is permeated by magnetic fields emerging from the sun and, inturn, ejects particules and magnetic field into the heliosphere. It isof prime importance to measure the coronal magnetic field to understand mechanisms at work in the corona. We explain why Dome C isexpected to be an outstanding site for such observations and describethe Solar Brightness Monitor we prepare to probe sky background andaerosols levels at this site. We also discuss coronal observations Dome C could allow to obtain.

The Square Kilometre Array is a global project to develop the nextgeneration radio telescope at metre to centimetre wavelengths. It willhave a collecting area of order one million square metres, asensitivity 100 times higher than the extended VLA, an instantaneousfield of view (FOV) larger than the full moon, and, in some designs,more than one FOV allowing multiple simultaneous use. It will be anextremely powerful survey telescope with the capability to follow upindividual objects with high angular and time resolution. The SKA willreach a point source sensitivity of 25 nano-Jy in 1 hour ofintegration, and a maximum resolution of better than 1 milli-arcsecond at20 GHz with excellent imaging over several orders of magnitude at anygiven frequency. The SKA science reach will be enormous, allowing newdiscoveries in astroparticle physics and cosmology, fundamentalphysics, galactic and extragalactic astronomy, and solar systemscience. Technological innovation, closely paralleling commercial ITdevelopments, is key to the design concepts under investigation and tothe cost goal of USD 1000/m2. The selection of technologies for theSKA is scheduled in early 2008. A number of possible locations for thetelescope are under investigation with a choice scheduled in early2006. Construction of the array will take most of the next decade.


All stars end through a phase where they form copious amounts of dust either in a stellar outflow or following explosive events. The most efficient dust factories seem to be stars that evolve through the Red Giant stage and form for several 105 yrs, dust in a cool stellar wind. The dust returned by them triggers the interstellar dust cycle and therefore is vital for the matter cycling in space. We discuss the theoretical basis for calculating the dust production by such stars. First, some elements of the theory of chemical equilibrium condensation calculations are presented and it is then discussed how the concept of activities can be used to also study non-equilibrium condensation. Then we discuss how dust particle growth in stellar winds can be calculated and which kind of input data are required for such calculations. Finally some results for dust production by AGB stars are discussed.


In the past years a wealth of observationsallowed to unravel the structural properties of the Dark Matter Halos around spirals. First, their rotation curves followan Universal profile (URC) that can be described in terms of an exponential thin stellar disk and adark halo with aconstant density core, whose relative importance increases with galaxy luminosity. Careful studies of individual objects, from dwarfs to giants, reveal that dark halos have a core, whose size r0 correlates with the central density ρ0.These properties are in serious discrepancy with the cuspy density distribution predicted by N-body simulations in collisionless ΛCDM Cosmology.

In NLTE computations of trace elements in stellar atmospheres, background opacities are generally treated in LTE. It is thus important to assess the impact of different methods of including this background opacity on the statistical equilibrium of the trace element and its resulting NLTE abundance. This article illustrates these effects using two examples, nitrogen in Vega and carbon in the Sun.

New observations of stellar pulsations, particularly from the CoRoT and Kepler space missions, have opened completely new possibilities for asteroseismic investigations for stars in large parts of the Hertzsprung-Russell diagram. Particularly dramatic has been the development of asteroseismology of stars showing solar-like oscillations, where hundreds of stars near the main sequence and tens of thousands of red giants can now be investigated. Although the analysis of the data have yielded extensive information about the global properties of the stars we are still only at the beginning of learning how to use the data for more profound studies of stellar interiors. Here I give a brief overview of the observations and discuss the potential contributions to the understanding of stellar physics.

Pulsating variable stars are powerful tools to study the structure and evolution of galaxies. Among different types of pulsating variables the Classical Cepheids trace the young stellar component in galaxies, and are one of the most important primary stellar distance indicators in establishing the cosmic distance scale. Instead, the RR Lyrae stars, with ages comparable to the age of the Universe, eyewitnessed the processes occurring in the very early times of galaxy formation, and thus can provide hints on how galaxies have formed. The role played by the pulsating variable stars in our understanding of the galactic structure and evolution is briefly reviewed in light of the promises of the scientific exploitation of the Gaia mission.