We have recently identified a previously unknown radial migration mechanism resulting from the overlap of spiral and bar resonances in galactic discs (Minchev & Famaey 2010; Minchev et al. 2010b). This new mechanism is much more efficient than mixing by transient spirals and its presence is unavoidable in all barred galaxies, such as our own Milky Way. The consequences of this are a strong flattening in the metallicity gradient in the disc, an extended disc profile, and the formation of a thick disc component, all taking place in only a couple of Gyr. This timescale is drastically shorter than previously expected and thus can put strong constraints on the longevity, strength and pattern speeds of the Galactic bar and Spiral Structure.

Recently, it has been suggested that the metallicity aversion of long-duration gamma-raybursts (LGRBs) is not intrinsic to their formation, but rather a consequence of theanti-correlation between star-formation and metallicity seen in the general galaxypopulation. To investigate this proposal, we compare the metallicity of the hosts ofLGRBs, broad-lined Type Ic (Ic-bl) supernovae (SNe), and Type II SNe to each other and tothe metallicity distribution of star-forming galaxies using the SDSS to represent galaxiesin the local universe and the TKRS for galaxies at intermediate redshifts. The differingmetallicity distributions of the LGRB hosts and the star-formation in local galaxiesforces us to conclude that the low-metallicity preference of LGRBs is not primarily drivenby the anti-correlation between star-formation and metallicity, but rather must beoverwhelmingly due to the astrophysics of the LGRBs themselves. Three quarters of our LGRBsample are found at metallicities below 12+log(O/H) < 8.6, whileless than a tenth of local star-formation is at similarly low metallicities. However, ourSN samples are statistically consistent with the metallicity distribution of the generalgalaxy population. Using the TKRS population of galaxies, we are able to exclude thepossibility that the LGRB host metallicity aversion is caused by the decrease in galaxymetallicity with redshift. The presence of the strong metallicity difference between LGRBsand Ic-bl SNe largely eliminates the possibility that the observed LGRB metallicity biasis a byproduct of a difference in the initial mass functions of the galaxy populations.Rather, metallicity below half-solar must be a fundamental component of the evolutionaryprocess that separates LGRBs from the vast majority of Ic-bl SNe and from the bulk oflocal star-formation.

In this course, I will review the main properties of internal gravity waves, andexamine how they can lead to particle and angular momentum transport in stars. Iwill then present some recent results that have been obtained for angularmomentum transport which show that waves are an important ingrediant of stellar modelling.

In a first part of the paper we give a simple introduction to the free space propagation of light at the level of a Master degree in Physics. The presentation promotes linear filtering aspects at the expense of fundamental physics. Following the Huygens-Fresnel approach, the propagation of the wave writes as a convolution relationship, the impulse response being a quadratic phase factor. We give the corresponding filter in the Fourier plane. As an illustration, we describe the propagation of wave with a spatial sinusoidal amplitude, introduce lenses as quadratic phase transmissions, discuss their Fourier transform properties and give some properties of Soret screens. Classical diffractions of rectangular diaphragms are also given here. In a second part of the paper, the presentation turns into the use of external occulters in coronagraphy for the detection of exoplanets and the study of the solar corona. Making use of Lommel series expansions, we obtain the analytical expression for the diffraction of a circular opaque screen, giving thereby the complete formalism for the Arago-Poisson spot. We include there shaped occulters. The paper ends up with a brief application to incoherent imaging in astronomy.

In a few years, the VLTI will be able to combine light from 4 to 8telescopes equipped with adaptive optics. In order to exploit thefull VLTI infrastructure, a second generation instrument, based onthe densified pupil concept (VIDA), has been proposed for veryhigh resolution direct imaging and coronagraphy. This paperpresents some possible coronagraphic devices providing a totalstar extinction on the VLTI when there are no phase errors.Lastly, the expected performances considering cophasing andadaptive optics residual errors are also presented.

We discuss the potential role that tidal flows in asynchronous binary stars may play in transporting chemically enriched material from deep layers towards the surface and the corresponding observational consequences of these processes. We suggest that the time-dependent velocity field induced by asynchronous rotation may contribute significantly to the mixing, thus providing a channel for the formation of chemically enriched slowly rotating massive stars.

Observations of spectroscopic double stars with long baseline optical interferometry have resolved many pairs, allowing their orbits to be measured and stellar masses and distances to be derived. A number of these measurements have accuracies worthy of comparison with high quality results from eclipsing binaries, thus able challenge stellar evolution models. I will review the contributions, and also show recent results, among them observations of massive O-stars and multiple systems.

Finite Difference and Finite Element algorithms for the solution of the radiative transfer equationas required for the modeling of modern high quality observations are briefly describedand discussed. It is emphasized that in the Finite Element approach there is the possibility to obtain an a-posteriori error estimator, which allows to locally refine the grid and in this way to obtain numerical solutions that do not differfrom the (unknown) analytical solutions by more than a prescribed tolerance.

"Densified-pupil multi-aperture imaging interferometers" also called "hypertelescopes" can provide direct images at their focal plane. Coronagraphic masking is applicable for nulling a star's image and searching associated planets. The scheme is applicable at the infra-red wavelengths where a planet has its best contrast, but also potentially at visible wavelengths where chlorophyll-like spectral features are to be searched. In the infra-red, where zodiacal and exo-zodiacal clouds tend to contaminate the image, the scheme provides a better rejection of this contamination than schemes using a beam-splitter and flat interference. For a typical Earth-like exo-planet the detection time is reduced 10 to 100 times. In the visible, planets are often resolved from their star by an interferometer's sub-aperture. Visible coronagraphy is then achievable in each sub-aperture before combining the beams and producing the high-resolution image. This relaxes the piston tolerances. Whether for sub-apertures or a densified pupil, or even a conventional telescope, multiple stages ofcoronagraphy are of interest, if equipped with as many deformable mirrors or transmissive plates. Located in the successive image planes, such adaptive correctors can phase the residual stellar speckles without affecting the planet peak. This generates a central peak of starlight, which can be masked without much obstructing the planet's wavefront. A design concept studied for an "Exo-Earth Discoverer", a hypertelescope variant proposed to NASA for its Terrestrial Planet Finder, involves 37 mirror elements of 1 m, driven by small solar sails and arranged to form a 40-300 m diluted spherical mirror. One or several focal combiners move along the focal surface. Optical solutions have been explored in preliminary detail.

Gamma-ray bursts (GRB) are extremely energetic events and produce highly diverse lightcurves. Light curves are believed to be resulting from internal shocks reflecting theactivities of the GRB central engine. Hence their temporal studies can potentially lead tothe understanding of the GRB central engine and its evolution. The light curve variabilitytime scale is an interesting parameter which most models attribute to a physical origine.g., central engine activity, clumpy circum-burst medium, orrelativistic turbulence. We develop a statistical method to estimate the GRB minimumvariability time scale (MVT) for long and short GRBs detected by GBM. We find that the MVTof short bursts is distinctly shorter than that for long GRBs supporting the possibilityof a more compact central engine of the former. We find that MVT estimated by this methodis consistent with the shortest rise time of the fitted pulses. Hence we use the fittedpulse rise times to study the evolution of burst variability time scale. Variability timeis in turn related to the minimum bulk Lorentz factor. Using this we relate the GRBspectral evolution to the evolution of the variability time scale.

The status of the AMICA project is reported. Final tests are currently running at Teramo Observatory before moving the instrument to Antarctica. AMICA is a camera equipped with two array detectors to perform astronomical imaging in the 2–28 μm band. It will be mounted at the IRAIT focal plane. Its very special feature is the antarctic operability. AMICA subsystems have been tested at typical antarctic conditions, in order to adopt technological solutions that ensure the correct operation of AMICA even on the antarctic plateau. Moreover, since human operations are not possible during the antarctic “winter", AMICA has been designed to operate in a completely automatic mode. AMICA is essentially aimed to demonstrate the potential of Antarctica for Infrared Astronomy and should therefore produce significant data, both for astronomy and site-testing. In addition, the experience gained in its technological development will be useful for building future astronomical instruments for extreme environment sites.

We show that the X-ray emission observed towards the center of our Milky Way Galaxy is consistent with a strong (2.1 M⊙/yr) outflow powered by both cosmic-ray pressure and thermal-gas pressure. In addition, the inferred launch parameters of such an outflow seem consistent with conditions inferred in the central Milky Way and other galaxies (although it is not clear if a significant vertical magnetic field exists in the center of the Galaxy). We also show that in galaxies with cosmic-ray pressure, gas pressure, and a vertical magnetic field component, cosmic-ray pressure can yield outflows over a wider range of conditions.

Directional detection is a promising search strategy to discover galactic Dark Matter. We present a Bayesian analysis framework dedicated to data from upcoming directional detectors. The interest of directional detection as a powerful tool to set exclusion limits, to authentify a Dark Matter detection or to constrain the Dark Matter properties, both from particle physics and galactic halo physics, will be demonstrated.


We report our recent progress on extragalactic spectroscopic and continuum observations,including HCN(J=1–0), HCO+(J=1–0), and CN(N=1–0) imaging surveys of local Seyfert and starburst galaxies using the Nobeyama Millimeter Array,high-J CO observations (J=3–2 observations using the Atacama Submillimeter Telescope Experiment (ASTE) and J=2–1 observations with the Submillimeter Array) of galaxies, and λ 1.1 mm continuum observations of high-z violent starburst galaxiesusing the bolometer camera AzTEC mounted on ASTE.

Chondritic meteorites constitute the most ancient rock record available in the laboratory to study the formation of the solar system and its planets. Detailed investigations of their mineralogy, petrography, chemistry and isotopic composition and comparison with other primitive solar system samples such as cometary dust particles have allowed through the years to decipher the conditions of formation of their individual components thought to have once been free-floating pieces of dust and rocks in the early solar nebula. When put in the context of astrophysical models of young stellar objects, chondritic meteorites and cometary dust bring essential insights on the astrophysical conditions prevailing in the very first stages of the solar system. Several exemples are shown in this chapter, which include (1) high temperature processes and the formation of chondrules and refractory inclusions, (2) oxygen isotopes and their bearing on photochemistry and large scale geochemical reservoirs in the nebula, (3) organosynthesis and cold cloud chemistry recorded by organic matter and hydrogen isotopes, (4) irradiation of solids by flares from the young Sun and finally (5) large scale transport and mixing of material evidenced in chondritic interplanetary dust particles and samples returned from comet Wild2 by the Stardust mission.

We discuss the support for the cooling of gas directly at the disk-halo interface as a mechanism to continually fuel a galaxy. This may be an important reservoir as there is not enough cold gas observed in galaxy halos and simulations indicate the existing cold clouds will be rapidly destroyed as they move through the surrounding halo medium. We show possible evidence for a net infall of the WIM layer in the Milky Way, simulation results showing the recooling of warm clouds at the disk-halo interface, and GALFA HI data of small, cold HI clouds that could represent this recooling.

We present the results of the analysis of our recent interferometric observations of Betelgeuse, using the AMBER instrument of the VLTI. Using the medium spectral resolution mode (R ~ 1500) we detected the presence of the water vapour and carbon monoxide (CO) molecules in the H and K bands. We also derived the photospheric angular diameter in the continuum. By analysing the depth of the molecular lines and the interferometric visibilities, we derived the column densities of the molecules, as well as the temperature and the size of the corresponding regions in the atmosphere of Betelgeuse (the MOLsphere) using a single shell model around the photosphere. Our results confirm the findings by Perrin et al. (2004) and Ohnaka et al. (2011) that the H2O and CO molecules are distributed around Betelgeuse in a MOLsphere extending to approximately 1.3 times the star’s photospheric radius.

Recent systematic surveys providing massive datasets of white dwarf stars show that there is still a deficit of a factor of 2.5 in the ratio of white dwarfs showing helium absorption lines to those with hydrogen absorption lines in the temperature range 30 000 K < Teff < 45 000 K. Since all white dwarfs have to evolve through this temperature range along similar sequences in the color-magnitude diagram, this implies that most of the helium atmosphere white dwarfs evolve into hydrogen atmosphere hot DA stars in that temperature range and then back again to helium atmosphere white dwarfs. I describe possible scenarios for this chameleon-like disguises of white dwarfs with helium dominant atmospheres and a new kind of pulsating white dwarfs predicted to appear near the lower end of the temperature range 45 000–30 000 K from these scenarios. Recently searches have discovered a pulsating DA white dwarf, WD1017−138, in the predicted temperature range. This discovery opens the possibility of a direct test of the explanation for the deficit of helium atmosphere white dwarfs at these temperatures by asteroseismic probing of the atmospheric layers of the hot DAV stars.

Non-LTE modelling for a particular atom requires accurate collisional excitation and ionization cross-sections for the entire system of transitions in the atom. This review concerns with inelastic collisions with electrons and neutral hydrogen atoms. For the selected atoms, H i and Ca ii, comparisons are made between electron impact excitation rates from ab initio calculations and various theoretical approximations. The effect of the use of modern data on non-LTE modelling is shown. For most transitions and most atoms, hydrogen collisional rates are calculated using a semi-empirical modification of the classical Thomson formula for ionization by electrons. Approaches used to estimate empirically the efficiency of hydrogenic collisions in the statistical equilibrium of atoms are reviewed.