Much progress has recently been made in understanding and quantifying vertical mixing induced by double-diffusive instabilities such as fingering convection (usually called thermohaline convection) and oscillatory double-diffusive convection (a process closely related to semiconvection). This was prompted in parts by advances in supercomputing, which allow us to run Direct Numerical Simulations of these processes at parameter values approaching those relevant in stellar interiors, and in parts by recent theoretical developments in oceanography where such instabilities also occur. In this paper I summarize these recent findings, and propose new mixing parametrizations for both processes that can easily be implemented in stellar evolution codes.

The equation of transfer is a two-faced equation, easy to solve at times, and difficult to solve at other times, depending on the values assumed by its coefficients. It is rather tractable when applied to the deep layers of atmospheres and for frequencies from their continuum spectrum, but this solvability is in stark contrast to the difficulty in solving it close to the surface of atmospheres or within spectral lines. It follows that the photons most rich in information that reach our telescopes are also the most difficult to interpret. The purpose of this note is to stress this point and to illustrate it with some examples taken from the solar atmosphere.

In the current cosmological scenario, part of the linearly polarizedemission of the CMB is expected to be rotational (B-modes). Thiscomponent is due to tensor perturbations of the metric produced byprimordial gravitational waves, which are generated a split-second after theBig Bang. The signal expected is of the order of ≲ 0.1 μK, well below the non-rotational component of the polarizationsignal (E-modes), and beyond the sensitivity of present generationinstruments. New, more sensitive instruments are developed inseveral labs, with the goal to measure the B-modes. Control ofsystematics and foregrounds will be the key to make the results ofthese experiments believable. In this paper we shortly outlineBRAIN, a bolometric interferometer devoted to B-modes research,and its pathfinder experiment, devoted to test the Dome-C site.


This paper presents an ultra low noise instrumentation based on cryogenic electronic integrated circuit. We have designed an ASIC (Application Specific Integrated Circuit) in standard BiCMOS SiGe 0.35 μm AMS technology. The main functions of this circuit, the readout and the control of a 24 to 1 SQUID multiplexer, is presented. We also report the cryogenic operation of each part of this ASIC.


The solar interior has been scrutinized by two different and independent probes during the last twenty years with important revisions of the solar model, including a recent heavy element abundancerevision. Today, we get a quantitatively coherent picture (even incomplete) of the solar (stellar) radiative zones. In this review, we recallthe clues for solar gravitational settling definitively established by the seismic determination of the photospheric helium content. We comment also on the need for mixing in the transition region between radiation and convectionin the case of the Sun and of population II stars. We finally list the open questions and the importance to continue more precise investigations of the solar (stellar) radiative zone in detecting gravity modes with the project DynaMICS.

The ESA Gaia mission will provide a multi-epoch database for a billion of objects,including variable objects that comprise stars, active galactic nuclei and asteroids. Wehighlight a few of Gaia’s properties that will benefit the study of variable objects, andillustrate with two examples the work being done in the preparation of the data processingand object characterization. The first example relates to the analysis of the nearlysimultaneous multi-band data of Gaia with the Principal Component Analysis techniques, andthe second example concerns the classification of Gaia time series into variability types.The results of the ground-based processing of Gaia’s variable objects data will be madeavailable to the scientific community through the intermediate and final ESA releasesthroughout the mission.

Dust forming systems, in which a phase transition between the gas phase and the solid state takes place, are seriously affected by the presence of dust, which causes tight, non-linear interactions between various physical and chemical processes. As a consequence, the dynamics of, e.g., a stellar atmosphere and the formation ofdust grains are inseparably connected. Chemical conditions, dust formation, and dust-induced instabilities in such non-linearly coupled systems as well as some implications regarding stellar evolution are discussed.

ESPaDOnS is a new-generation cross-dispersed échelle spectropolarimeter, the commissioning phase of which is scheduled at the Canada-France-Hawaii Telescope (CFHT) for autumn 2003. This instrument will provide full coverage of the optical domain (370 nm to 1000 nm) in all polarization states (circular and linear) at a resolving power of about 70 000, with a peak efficiency of 20% (telescope and detector included). It includes a bench-mounted spectrograph, fiber-fed from a Cassegrain-mounted module including all polarimetric and calibration facilities. ESPaDOnS should be the most powerful tool dedicated to stellar spectropolarimetry, therefore opening unprecedented perspectives for major issues of stellar physics, from studies of stellar interiors to investigations of stellar atmospheres, stellar surfaces, stellar magnetic fields, and to observations of circumstellar environments and extra-solar planets.

The CEA, in coordination with IPEV and LUAN, will prepare an experiment to study frost formation on surfaces in radiative cooling in the winter. This experiment has been shipped to be installed at Concordia before the 2007 winter period. It will be controlled from Concordia winterover personal, through PC server that will locally archive data from WEBcams and several local heat regulators. This experiment will be used to give recipes on the way to compensate with heaters the radiative cooling from the sky and maintain instrument surfaces at temperature just above icing conditions. The individual regulators proposed in this experiment will be usable as standalone ice protection systems for existing and future telescopes.

The small-scale surface granulation on cool main-sequence stars and white dwarfs influences the overall appearance of these objects only weakly. And it is only indirectly observable by analyzing e.g. line-shapes or temporal fluctuations – except for the Sun. The large-scale and high-contrast convective surface cells and accompanying sound waves on supergiants and low-gravity AGB stars on the other hand have a strong impact on the outer atmospheric layers and are directly detectable by interferometric observations.

Necessary to interpret modern observations with their high resolution in frequency, time, and/or space are detailed numerical multi-dimensional time-dependent radiation-hydrodynamical simulations. Local simulations of small patches of convective surface layers and the atmosphere of main-sequence stars have matured over three decades and have reached an impressive level of agreement with observations and also between different computational codes. However, global simulations of the entire convective surface and atmosphere of a red supergiants are considerably more demanding – and limited – and have become available only for about one decade.

Still, they show how the surface is shaped by the interaction of small surface granules, that sit on top of large envelope convection cells, and waves, that can travel as shocks into the outer atmosphere. The route to more complete future models will be discussed, that comprise the outer atmosphere of the stars and that could explain some of the little-understood phenomena like chromosphere, molsphere, or wind-formation.

We present the initial performance of the Gaia Radial Velocity Spectrometer, providing an overview of its performance, which is essentially nominal in terms of spectral resolution, throughput and operation, except for the presence of unexpectedly high levels of scattered background. This is mainly Solar in origin, and reduces the limiting magnitude for radial velocity measurements by ∼1 magnitude to V  ∼ 16. Radial velocity calibration accuracies are compliant with requirements.

We have used the CFHT and Gemini South telescopes to obtain high-resolution, high signal-to-noise optical and near-infrared spectra of several lines of neutral helium in a number of helium-peculiar, HgMn and related stars. Since the helium lines observed have 3He isotope shifts of up to 1 Å and sample a large range of continuous opacities in the program stars, these spectra are being used to search for the presence of 3He in their photospheres and, where 3He is present, examine the possible stratification of both isotopes of helium in their atmospheres. Analysis of a number of previously identified 3He stars provides strong evidence for different vertical stratification profiles of 3He and 4He in these stars. 4He is generally enhanced deep in the photospheres but sharply depleted high in the atmospheres while 3He appears to be confined to a narrow layer above the 4He.

The low scintillation noise and the long continuous darkness areamong the unique properties of the Dome-C site on the eastAntarctic plateau. Ultra-high precision optical photometry istherefore among the techniques best suited for this particularsite. We propose a telescope (ICE-T) optimized for ultra-high andultra wide field photometry for Dome C. It consists of two 60 cmoptical ultra-wide-field Wynne-Schmidt telescopes and one 18 cmnarrow-field Maksutov spectrophotometric telescope on a singlemount. ICE-T is currently a team effort of the GermanAlfred-Wegener-Institute for Polar Research, the ItalianUniversities of Padova and Perugia, the INAF Observatory Catania,and the Catalonian IEEC in Barcelona, Spain, and the AIP, withcollaboration from the University of New South Wales, Australiaand the University of St. Andrews, UK. In this paper, I discusssome of the many problems associated with sub-milli-magphotometry.

This contribution aims to give a brief overview of the nature of the dust in the interstellar medium, its rôle there, where it comes from, what happens to it while it resides there and what are some key outstanding dust issues that yet need further attention.

I consider the relation of explanations for the observed data to testability in the following contexts: observational and experimental detection of dark matter; observational and experimental detection of dark energy or a cosmological constant Λ; observational or experimental testing of the multiverse proposal to explain a small non-zero value of Λ; and observational testing of the possibility of large scale spatial inhomogeneity with zero Λ.

Interstellar ices are widely observed in the infrared spectra of regions where stars and planetary systems form. Photochemical and thermal evolution of these ices is simulated and studied in our laboratory where the resulting production of complex organic residues is routinely performed. Observations of their variability with slightly different starting chemical conditions can be performed by means of infrared spectroscopy. Organic residues have interesting chemical properties that make them good potential candidates for prebiotic chemistry. Numerous other analytical methods (GC-MS, HPLC, mass spectrometry, etc.) can be combined to refine the knowledge of their chemical composition and structure. We present here some results on the obtained organic residue resulting from subsequent heating and sublimation of the irradiated ices which show the formation of some macromolecular species.

PLATO is a fully-robotic observatory designed for operation in Antarctica. It generates its own electricity (about 1 kW), heat (sufficient to keep two 10-foot shipping containers comfortably above 0°C when the outside temperature is at -70°C), and connects to the internet using the Iridium satellite system (providing ~30 MB/day of data transfer). Following a successful first year of operation at Dome A during 2008, PLATO was upgraded with new instruments for 2009.

PAHs are traditionally thought to form around carbon-rich AGB stars,where the presenceof inner-wind shocks and nucleation seeds can aid their formation. However,my recent workhas shown that the formation of benzene – thought to be the rate-limiting step in theformation of larger PAHs – can be efficient in other environments,namely the dense toriaround the evolved stars of pre-planetary nebulae and in the inner regions of theaccretion discs around young stars. I will discuss the chemical pathways to the formationof benzene in these regions and the subsequent formation of larger PAHs.

We review observational results of PAH emission in harsh interstellar environments, whichare mostly based on recent works by Spitzer and AKARI. The harsh environments includeshock regions in our Galaxy, the ionized superwinds and haloes of external galaxies, andthe hot plasmas of elliptical galaxies. Owing to the unprecedented high sensitivity forPAH emission with Spitzer and AKARI, it is found that an appreciable amount of PAHs arepresent in some cases with such hostile conditions. Some of them exhibit unusual PAHinterband strength ratios, reflecting either evolution of PAHs or physical conditions ofthe ISM. The distribution of the PAH emission, as compared to that of dust emission, isshown to discuss their ways of evolution and survival.

We present “A STEP” (Antarctica Search for Transiting ExtrasolarPlanets), a project dedicated to the search for planetary transitsfrom Antartica. The project consists of a semi-automatic ~40 cmtelescope equipped with a 16-million-pixel CCD installed at DomeC. The site offers crucial assets for a ground-based exoplanet transitsearch: uninterrupted phase coverage, excellent weather, low air-massvariations and reduced scintillation.
This system would be able to detect Pegasids transiting in front ofstars as faint as magnitude sixteen and could also detect smallerplanets in close-in period around brighter stars. This short termproject is meant to be a photometric qualifyer for the site and thefirst stage of a massive detection campaign. A mid-term objective of1000 detections for 2012 could be achieved either with many smalltelescopes or with a large Schmidt telescope with a large field ofview.
The project is relatively simple and cost-effective, and has thedouble purpose of qualifying the site and obtaining first-classscientific results. Our team is already familiar with transitdetection with an automated telescope and cold temperaturequalification.