The difficult goal of directly detecting a planet around a star requiresto cancel as much as possible the stellar light.Since the first proposal by Bracewell of a nulling interferometer, where thestar is put on a central dark fringe, several interferometricconfigurations have been presented in order to improve the quality ofthe rejection, especially to avoid the leaks due to the finite angular dimensionof the stellar disk, resolved by the interferometer. In the Bracewell interferometer, the behaviour of the nulling efficiency vs the angular distance θ to the star is as (1-cosθ)∝ θ2. One goal is to increase the exponent of the term θn whichgives the cancellation efficiency. I present one method to define configurations of telescopes positions, sizes and phase-shift that canachieve any given power of θ. The principle is based on a peculiar property foundby Prouhet of a partition into two sets of the integers, done according to the Thué-Morse sequence.2L telescopes regularly spaced on a line, are distributed into two groups, following their rankin the Thué-Morse sequence and, to the telescopes of one of the groups, is applied a π phase shift. The result is a fractal-like distribution of the telescopes where redundancy is minimum andwhose interferometric combination produces a very efficient nulling in θ2L.I first examine 1-D patterns of identical telescopes, then extend the method to 2-D configurations, then show that the lattercan be used to define 1-D arrays of non identical telescopes, according to some algebra of interferometers. The generalizationto arrays where the phase shift between n groups of telescopes is 2kπ/n is finally proposed.

Observations of jet- like phenomena near the solar limb are reported for a long time, first in Hα (Secchi observations of spicules in the 1870 ies), and after, from eclipse high resolution coronal images taken in white-light (1920–1973) as spiky structures. EUV jets were reported in the 70 ies from rocket and space-borne CIV filtergrams and finally X-EUV jets were reported from SXT observations of Yohkoh and from EIT and CDS SoHO observations. There is now little doubt that they are of magnetic origin although no magnetic field measurements exist for these regions and thermo-dynamical models are still work out. New observations of both spicules and jets with the SOT/SXT of Hinode were subjected to an analysis showing the influence of the null point(s) of the magnetic field. The collective behavior of the H CaII SOT(Hinode) time sequences of processed with the Madmax operator images of limb spicules show the torsional effects which were partly suggested before from the interpretation of high resolution limb spectra taken on Russian coronagraphs and the VTT at SacPeak. 100 s and shorter period waves are recorded. We propose a reconnection process occurring at the top of an emerging twisted flux tube for explaining some peculiarities of the spicular eruptions and possibly, as a viable mechanism for explaining the SXR jet eruptions. The result of a numerical 3D modeling illustrates this erupting mechanism although the behavior of the magneto-plasma structure near a null point, as shown by coronal filtergrams, does not necessary imply reconnections, especially the case of jets making a long coronal ray we observed in white-light with Lasco C2.

Recent advances in the determination of stellar abundances and their impact on thestudy of nucleosynthesis and the chemical evolution of galaxies are discussed. It is argued thatdetailed interpretation of the abundance patterns among chemical elements foundat different metallicities still requires solid spectroscopic data. Despite current improvementsin abundance analyses, these are not, however, free from systematic errors which can hidethe real history of the chemical evolution. Some examples are discussed.


We explore the problems of determining the abundance of Si in a numberof hot Ap stars.

In this paper, some basics concepts in statistical approachesfor detection of signals embedded in noise are brieflyreviewed. Though most material presented in the first part ofthe paper is well documented in the litterature (seereferences), some effort is made to provide a self-containedand concise introduction to the subject. The importance andrelevance of the likelihood ratio is highlighted from aBayesian formulation of the problem; the optimal (in the senseof maximized detection probability for given false alarm rates)Neyman Pearson test and likelihood ratio test are discussed inthe general framework of test performance studies. Therefore,the usefullness of the ROCs (Receiver OperatingCharacteristics) is illustrated on simple examples. When someunknown parameters must be taken into account, extension of theprevious approaches are mentionned, with some emphasis put onthe GLRT (generalized likelihood ratio test). Most resultsintroduced in this tutorial are then applied and discussed inthe framework of the extra-solar planet detection problem. Aobservation model involving Poisson random variables isstudied. A thorough study in performed, and the Gaussianasymptotics are discussed in the case where all parameters ofthe model are assumed. In a more realistic situation where someparameters must be estimated, the GLRT is derived and itsperformances are evaluated by Monte Carlo simulation.

At Dome C most of the seeing is located in the lower atmosphere, below 50 meters height.In this introduction we describe ways in which one might mitigate those ground layer seeingeffects and thus be limited solely by the ~0.25 arcsec seeing of the so-called“free atmosphere”.

It has recently been suggested that the peculiar cluster Pal 1 is associated to the Canis Major dwarf galaxy, which existence is still at the center of a debate. Our first measurement of the cluster’s chemical abundance ratios allows us to examine this association and to advance further in the clarification of Pal 1 possible origin.

Studying the internal structure of exoplanet-host stars compared to that of similar stars without detected planets is particularly important for the understanding of planetary formation. The observed average overmetallicity of stars with planets is an interesting point in that respect. In this framework, asteroseismic studies represent an excellent tool to determine the structural differences between stars with and without detected planets. It also leads to more precise values of the stellar parameters like mass, gravity, effective temperature, than those obtained from spectroscopy alone. Interestingly enough, the detection of stellar oscillations is obtained with the same instruments as used for the discovery of exoplanets, both from the ground and from space. The time scales however are very different, as the oscillations of solar type stars have periods around five to ten minutes, while the exoplanets orbits may go from a few days up to many years. Here I discuss the asteroseismology of exoplanet-host stars, with a few examples.

This paper discusses numerical simulations performed in order tobetter understand the dynamics of various physical processes present in theradiative regions of stars. Those processes includesemi-convection, Eddington-Sweet meridional circulationand anisotropic turbulence. The impact of some of those results onevolutionary models is also discussed.

As the SALT High Resolution Spectrograph is nearing completion, we plan to extend the Pennsylvania-Torun Planets Search (PTPS) with HET to the southern hemisphere. Due to overlap of the skies available for both HET and SALT in the declination range (+10, -10) deg, some cooperation and immediate follow-up is possible. Here we present, as an example, a ~1000 star sample of evolved stars for the future SALT Planet Search.

The ESA Gaia mission uses two telescopes to create the most ambitious survey of the Galaxy. The angle between them must be known with exquisite precision and accuracy. An interferometer: the Basic Angle Monitoring system measures its variations. High quality data have been retrieved and analysed for more than a year. A summary of the in-orbit performance and some early results are presented.

The detection is a real challenge for most of the UV-space missions. First, the classical detectors quantum efficiency is very low between 100 and 300 nm. The second point is that the useful flux is very low, and the photon counting is sometimes required. The stray light flux (visible light) is often strong so that additional filters are needed. In addition to the fact that these filters reduce the effective quantum efficiency, it is well known that the filter quality is a big constraint for the UV applications. For these reasons, dedicated detectors with high performances are required. Fortunately, strong improvement in detectors has been done for years and promising detectors are merging. After having reminded the different UV-space mission needs, this paper will present the available UV detectors. In the last part, the CNES Roadmap will be shortly discussed.

The Concordia Station (Candidi 2003), on the AntarcticaPlateau, will soon become one of the best observatories to performinfrared observations in the 2–20 μm atmospheric windows andbeyond, thanks to its low sky background, low temperature andhigh atmospheric transparency. The possibility of passivelycooling the telescope is a further advantage. We describe herethe first permanent Antarctic infrared telescope, underdevelopment for the Dome C base. It is the InternationalRobotic Antarctic Infrared Telescope (IRAIT). We briefly outlinea few scientific motivations for it, then we review the technicalcharacteristics and the status of its development. The infraredcamera for IRAIT is described in another dedicated paper in thisvolume.

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of interstellar magnetic fields. Total fields in gas-rich spiral arms and bars of nearby galaxies have strengths of 20–30 μG and are dynamically important. Ordered fields with spiral structure exist in grand-design, flocculent and even irregular galaxies. The strongest ordered fields of 5–10 μG are found in interarm regions, sometimes forming “magnetic spiral arms”. Faraday rotation sometimes reveals large-scale patterns which are signatures of coherent fields generated by dynamos, but in most galaxies the field has a complicated structure. – Magnetic fields with X-shaped patterns are observed in radio halos around edge-on galaxies. The synchrotron scale height allows to measure the mean outflow velocity, which seems to increase with the star-formation rate.

Gravitational settling and microscopic diffusion affects the main sequence lifetimes, main sequence turn-off luminosities and temperatures of metal-poor halo stars. As a result, the inclusion of diffusion in the stellar evolution models has important consequences for age determinations of old stars. In contrast, diffusion has little impact on the post-main sequence evolution of metal-poor stars. Observations of the heavy element abundances in turn-off and giant branch stars in the globular cluster NGC 6397 suggest that diffusion occurs in metal-poor stars, but that the diffusion must be inhibited by turbulent mixing.

COCHISE is a 2.6 meter millimetric telescope, mainly devoted to cosmological observations, located at Concordia. In this paper we report on the installation phases and preliminary operations performed with this instrument. At present, COCHISE is the largest telescope located at Concordia, for that reason it represents a pathfinder for future telescopes.

We present the Mirror Advanced technology Coronagraph (MAC) as a new generation solar telescope to be put at suitable high altitude coronal sites in order to resolve modern problems of solar physics, like the origin of the heating of the chromosphere and of the corona, the analysis of the mesospheric layers of the solar atmosphere and the effects of shearing the photospheric magnetic fields on the dynamics of the upper coronal layers.

The THz spectral region includes a number of important transitions which allow us to trace the evolution of the interstellar medium. Because of the opacity of the atmosphere in this spectral range, the best sites for ground-based THz observations are on the Antarctic Plateau; of these sites, Dome A is expected to be the best. THz survey science can be carried out with small telescopes, easing logistical constraints. By deploying a submillimetre-wave tipper/ telescope to Dome A, we have trialled several technologies for such an instrument, and we are able to test whether the site quality is sufficient for THz surveys.

The interaction between stellar winds and the interstellar medium (ISM) can create complex bow shocks. We have studied the bow shock region around Betelgeuse using Herschel PACS images at 70, 100, and 160 μm and SPIRE images at 250, 350, and 500 μm. These data were complemented with ultraviolet GALEX data, near-infrared WISE data, and radio 21 cm GALFA-HI data.

The infrared Herschel images of the environment around Betelgeuse are spectacular, showing the occurrence of multiple arcs at  ~6–7′ from the central target and the presence of a linear bar at  ~9′. Remarkably, no large-scale instabilities are seen in the outer arcs and linear bar. The dust temperature in the outer arcs varies between 40 and 140 K, with the linear bar having the same colour temperature as the arcs. The inner envelope shows clear evidence of a non-homogeneous clumpy structure (beyond 15′′). The non-homogeneous distribution of the material even persists until the collision with the ISM. A strong variation in brightness of the inner clumps at a radius of  ~2′ suggests a drastic change in mean gas and dust density  ~32 000 yr ago. Using hydrodynamical simulations (see van Marle & Decin, these proceedings), we try to explain the observed morphology of the bow shock around Betelgeuse.

Different hypotheses, based on observational and theoretical constraints, are formulated to explain the origin of the multiple arcs and the linear bar and the fact that no large-scale instabilities are visible in the bow shock region. We infer that the two main ingredients for explaining these phenomena are a non-homogeneous mass-loss process and the influence of the Galactic magnetic field. The linear bar is probably an interstellar structure illuminated by Betelgeuse itself.

Applications of the theory of the optimal design of radial-velocity planet-search surveys are discussed. Two important practical problems are considered. The first problem is finding the time for future observations to yield the maximum improvement of the accuracy of exoplanetary orbital parameters and masses. In this case, the optimal scheduling rules are designed to maximize the determinant of the Fisher information matrix (the so-called D-optimality criterion). This method is asymptotically equivalent to the maximization of the expected gain of the Shannon information provided by making extra observations. The second problem is finding the most favourable observing time for distinguishing alternative orbital fits (the design of discriminating experiments). In this case, the optimal scheduling rules are designed to maximize the Kullback-Leibler divergence information.
We also consider the potential efficiency of these methods of optimal planning of radial velocity observations for multi-planet systems.