We develop a new version of a Cellular Automaton (CA) for the simulation of the dynamics of a stellar atmosphere sitting on top of an inert core, and specified by the following physical input parameters: mass, radius and luminosity of core, and mass of atmosphere. The CA incorporates various parametrised simulation schemes of the instability mechanism (essentially ionisation). The initial state in all of our numerical experiments is a radially symmetric atmosphere of exponential density run and uniform temperature (input parameters: density scale– height and temperature of atmosphere). The initial atmosphere is not in hydrostatic and thermal equilibrium. After a transient stage, the system relaxes, for certain ranges of the parameters of the instability mechanism, towards a state of nontrivial dynamical behaviour: Local heat–driven circulations are set up which may range from nearly stationary and spatially symmetric cellular patterns to temporally and spatially irregularly fluctuating velocity fields. The traditional radial symmetry of the density pattern is broken, so that the star acquires a globally non–spherical shape. The residual non–stationary component, when integrated over the star to produce the counterpart of an observational velocity curve of a variable star, shows an irregular cyclic behaviour which does not have the signature of low–dimensional deterministic chaos.

Imaging spectropolarimetry is a powerful tool in solar physics. Multichannel Subtractive Double Pass (MSDP) spectrographs can produce simultaneous 2D images in a number of wavelengths covering several line profiles with the following advantages:

- Contrary to long slit spectroscopy, the spatial resolution can reach the diffraction limit.

- Contrary to narrow band filters, full line profiles are recorded at the same time without any image motion and differential seeing effect.

MSDP spectrographs use an entrance window instead of the usual long slit. A new generation MSDP using slicers made of mirrors instead of prisms is proposed for the future 4 m class European Solar Telescope. We describe the beam slicer prototype S4I (Spectral Sampling with Slicer for Solar Instrumentation) that will be tested soon at the 14 m spectrograph of the Meudon Solar Tower.

A new multi-wavelength solar telescope, Optical and Near-infrared Solar Eruption Tracer (ONSET), is constructed by Nanjing University, being run in cooperation with Yunnan Astronomical Observatory. ONSET is able to observe the Sun in three wavelength windows: He I 10830 Å, Hα and white-light at 3600 Å or 4250 Å. Full-disk or partial solar images with a field of 10 arcmin at three wavelengths can be obtained nearly simultaneously. It is designed to trace solar eruptions with high spatial and temporal resolutions. This telescope has been installed at a new solar observing site near the Fuxian Lake, Yunnan Province. The site is located at E102N24, with an altitude of 1722 m. The seeing is stable and very nice. We give a brief description of the scientific objectives and the basic structure of ONSET. Some preliminary results are also shown.

High contrast imaging opportunties abound in astronomy, and some carry such intrinsic interest that they justify considerable effort to master the technical challenges. The field has a rich history dating back to the beginnings of electromagnetic theory, and ten years ago one might have been forgiven for thinking that the topic was passé. But just within the last decade the study has fluorished with major advances on multiple fronts - scientific as well as technical. The analytical and conceptual generalization of classical coronagraphy to include complex masks and apodizations has opened a fertile field of study. Nulling in interferometry and direct imaging has developed in several promising directions, with empirical and theoretical understanding sometimes passing via different routes to arrive at firm conclusions. Critical supporting technology is developing apace, often for reasons having little to do with high contrast imaging. Thus very large telescopes, space telescopes, adaptive optics, and ultra-precision optics are all steadily advancing, and thus building a priceless technological foundation for future high contrast imaging experiments and facilities. This chapter offers a brief, simple overview, intended primarily to give a context for the many detailed technical papers in this volume.

Our aim is to present new unified line profiles of sodium perturbed by H2 from the optical to the infrared spectral range. We compare the specific results obtained for the 3s-3p transition to laboratory spectra.

This paper reviews recent continuum surveys done at (sub)millimeter wavelengths towards z>3.7 quasars and observations of the CO line emission in high z sources.

The general formalism for Lyot and Roddier & Roddier coronagraphy is detailed. The influence of the masksize, chromatism and central obscuration are discussed. The necessity of entrance pupil apodization forcoronagraphy is introduced from the fundamental limitation that appears in the classical technique. Prolatespheroidal functions are presented as the natural apodizations for coronagraphy.

The complexity of composite spectra of close binary star system makes study of the spectra of their component stars extremely difficult. For this reason there exists very little information on the photospheric chemical composition of stars in close binaries, despite its importance for informing our understanding of the evolutionary processes of stars. In a long-term observational project we aim to fill this gap with systematic abundance studies for the variety of binary systems. The core of our analysis is the spectral disentangling technique, which allows isolation of the individual component star spectra from the time-series of observed spectra. We present new results for high-mass stars in close binaries. So far, we have measured detailed abundances for 22 stars in a dozen detached binary systems. The parameter space for the stars in our sample comprises masses in the range 8–22 M⊙, surface gravities of 3.1–4.2 (c.g.s.) and projected rotational velocities of 30–240 km s−1. Whilst recent evolutionary models for rotating single stars predict changes in photospheric abundances even during the main sequence lifetime, no star in our sample shows signs of these predicted changes. It is clear that other effects prevail in the chemical evolution of components in binary stars even at the beginning of their evolution.

GAIA will likely be a real milestone for asteroid science. Itsunprecedented astrometric accuracy can be exploited to compute orbitsbetter than those obtained by using the whole set of availableastrometric observations carried out from ground during the last 100 years. GAIA will make it possible to measure asteroid masses throughthe measurement of the tiny displacements caused by asteroid mutualencounters. This will be a major breakthrough for physical studies ofminor planets. Moreover, sizes will be also directly measured for abig sample of more than 1000 objects. From masses and sizes, estimatesof the average densities will be also obtained. The spectrophotometriccapability of GAIA will be used for purposes of taxonomicclassification, with important implications for surface mineralogicalcharacterization. Finally, GAIA will be an ideal platform to detectnear-Earth asteroids having orbits interior to that of the Earth.

The fate of metals after they are released in starburst episodes is still unclear. What phases of the interstellar medium are involved, and in which timescales? Evidence has grown over the past few years that the neutral phase of blue compact dwarf (BCD) galaxies may be metal-deficient as compared to the ionized gas of their H ii regions. These results have strong implications for our understanding of the chemical evolution of galaxies. We review here the main results and the main caveats in the metal abundance determination from far-UV absorption-lines. We also discuss possible scenarios concerning the journey of metals into the interstellar medium.

We discuss the role of Configuration Interaction (CI) and the influence of the number of configurations taken into account in the calculations of nickel and iron spectral opacities provided by the OPAC international collaboration, including statistical approaches (SCO, CASSANDRA, STA), detailed accounting (OPAS, LEDCOP, OP, HULLAC-v9) or hybrid method (SCO-RCG). Opacity calculations are presented for a temperature T of 27.3 eV and a density of 3.4 mg/cm3, conditions relevant for pulsating stellar envelopes.

We give examples of where the Heun function exists as solutions ofwave equations encountered in general relativity. While the Diracequation written in the background of Nutku helicoid metric yieldsMathieu functions as its solutions in four spacetime dimensions,the trivial generalization to five dimensions results in thedouble confluent Heun function. We reduce this solution to theMathieu function with some transformations. We must applyAtiyah-Patodi-Singer spectral boundary conditions to this systemsince the metric has a singularity at the origin.

Gaia will provide accurate parallaxes, spectrophotometry and spectroscopy for hundreds of thousands of emission-line stars across the whole HR diagram. In preparation for the Gaia mission, we are developing algorithms to recognize and classify emission-line stars. A large collection of ground-based spectroscopic observations has been collected and will be used for testing and training the algorithms.

Gaia will also provide information on several millions of early-type stars. Determining accurate parameters for these stars from Gaia data only will be difficult due to the AV – Teff degeneracy.

The conditions of thermodynamic equilibrium, local thermodynamic equilibrium, and statistical equilibrium are discussed in detail. The equations of statistical equilibrium and the supplementary equations are shown together with the expressions for radiative and collisional rates with the emphasize on the solution for trace elements.

Resonance broadening is important for the hydrogen lines in the spectra of F-type and later stars. In the corresponding temperature regime, the extended wings of the Balmer lines are used as a stellar effective temperature indicator. We show the effect of the use of two broadening theories, Ali & Griem (1965, 1966) and Barklem et al. (2000a, 2000b), on the effective temperature derived in non-LTE from Hα and Hβ in the Sun and the metal-poor star HD19445. Van der Waals broadening is important for strong spectral lines in the atmospheres of F-type and later stars. For the selected transitions in Ca I and Ca II, line profile comparisons are made between applying the van der Waals damping constants from laboratory measurements, the ABO perturbation theory, and the classic Unsöld approximation.

The paper starts from the rationale, already presented in 2004 at the firstToulouse meeting on astronomy at Dome C, to propose an infrared, wide-fieldImaging FTS (IFTS) as a first generation instrument behind a 2 to 3 moptical telescope. Such an instrument could fully take advantage of all theproperties of the site for imagery and spectroscopy and offer an instrumentpresently needed after the numerous imaging surveys. Simulations have beenconducted to define the range of field size and of resolution which couldbe reachable. Then, derived from the study of H2 Explorer (H2EX) an IFTSfor a space project, an optical design for a 2 to 25 μm instrument,imaging a 10'×10' field, has been developed, based on a dual ouputinterferometer, using cat's eyes retroreflectors in its arms. With amaximum optical path difference (OPD) of 30 cm a spectral resolution of105 at 2 μm (20 000 at 25 μm) is possible with this fieldsize, behind a PILOT-type telescope (2.4 m) and a minimum beam size of80 mm within the interferometer. With the same optics and the samemechanism of control of the OPD, two interchangeable beamsplitters (2 to5.5 μm and 6 to 25 μm) and the corresponding detector arrays (InSband Si:As) cover the entire spectral range. Theinstrument must be cryogenic (temperature around 50 K) to make the thermalbackground from the optics negligible. The best sensitivity is obtainedthrough narrow-band filters (2%) isolating lines in emission-lineregions. Such a survey instrument has never been built before. It calls fora dedicated telescope for the best use of this type of instrument on theDome C site.

We discuss models of AGB star atmospheres. Special emphasis is put onthe question of opacities, treatment of radiative transfer andsimulation of interferometric results.

The standard model of stellar structure is unable to account for various observational facts, such as anomalies in the surface composition, and there is now a broad consensus that some extra mixing must occur in the radiation zones, in addition to the always present convective overshoot or penetration. The search for the causes of this extra mixing started in the late seventies, and it was quickly realized – in particular by Sylvie Vauclair and her co-workers – that some mild turbulence must be present to counteract the effect of gravitational settling and radiative levitation. What could be responsible for this turbulence? One suggestion was the internal gravity waves emitted at the boundary of convection zones, but it is still not established whether these waves will lead to true mixing. However they transport angular momentum, and therefore they generate differential rotation, which may be shear-unstable and thus lead to turbulence. Another way to transport angular momentum and produce an unstable rotation profile is through the large-scale circulation which is induced by the structural adjustments as the star evolves, or by the torques applied to it (due to stellar wind, accretion, tides). These processes participate in what is called the “rotational mixing”; their implementation in stellar evolution codes – again under Sylvie's impulse – has given birth to a new generation of stellar models, which agree much better with the observational constraints, although there is still room for improvement.