Pi of the Sky is a system of wide field-of-view robotic telescopes which search for shorttimescale astrophysical phenomena, especially for prompt optical GRB emission. The systemis designed for autonomous operation, follows the predefined observing strategy and adoptsit to the actual conditions. We describe the current status of telescopes located in Chileand Spain and prospects for future development.

The emission properties of the components of the multiphase interstellar medium (ISM) require observations at very different wavelengths covering the range from X-rays for the hot phase to radio emission for the non-thermal component. This contribution gives an overview of the observational evidence for the presence of a multiphase ISM in halos of spiral galaxies. It is shown that the presence of halo gas correlates with the starformation rate in the disk. Recent radiocontinuum observations for NGC 253 are discussed with regard to the propagation of cosmic rays into the halos.

A review of some of the most important studies of the past several decades pertaining to the study of atomic diffusion in stellar atmospheres is presented. A brief description of various studies of radiative accelerations and diffusion calculations in stellar atmospheres is given. Several physical phenomena such as ambipolar diffusion, light-induced drift and the effect of magnetic fields on diffusion are discussed. Results from recent self-consistent model atmospheres including elemental stratification are also reviewed. Particularities of radiative acceleration calculations in stellar atmospheres as well as difficulties and future challenges related to diffusion calculations in stellar atmospheres are also presented.

The observed brightness fluctuations and large-scale structures on thesurface of the Red Supergiant Betelgeuse make the star a prime targedfor future interferometric measurements. At the same time, they openthe possibility to resolve these structures in numerical radiationhydrodynamics simulations of the entire star. After some general remarksabout the possibility and difficulties of 3D simulations of stars ingeneral results of such calcuations of the outer convective envelope andthe atmosphere of a Red Supergiant and a star on the Asmyptotic GiantBranch are presented. These show that numerous short-lived small-scalesurface granules coexist with a few long-lived large-scale envelopeconvection cells. Pressure fluctuations deform the star and influencethe surface convection. The convective “granulation" pattern differsfrom the solar one. Convection and pulsations produce large-scalehigh-contrast brightness fluctuations that might explain the observedluminosity variations and surface “spots”. Shock waves and supersonicatmospheric velocities manifest themselves in broad line profiles.

In this contribution we briefly introduce a mechanism for short gamma ray burst emissiondifferent from the usually assumed compact objects binary merger progenitor model. It isbased on the energy release in the central regions of neutron stars. This energy injectionmay be due to internal self-annihilation of dark matter gravitationally accreted from thegalactic halo. We explain how this effect may trigger its full or partial conversion intoa quark star and, in such a case, induce a gamma ray burst with isotropic equivalentenergies in agreement with those measured experimentally. Additionally, we show how theejection of the outer crust in such events may be accelerated enough to produce Lorentzfactors over those required for gamma ray emission.

Long hypothesized to be the origin of planetary systems, disks around newly formed stars have been studied in detail in the last twenty years. Most, if not all stars form surrounded by a disk, with typical masses of 0.001–0.3 M๏ and up to several hundred AU. Molecular emission lines show the gas to be in Keplerian rotation, with most species (but not H2) frozen out onto dust grains in the cold and dense disk interior. The fraction of stars with disks decreases from > 80% at < 1 Myr to < 10% at 10 Myr. The disk “half-life" is 2–3 Myr, with the inner and outer disks disappearing nearly simultaneously. There is a small but distinct populations of disks with cleared-out inner regions, so-called cold or transitional disks, explained by photoevaporation, planet formation, or binarity. Inside the disks, planet formation begins, with clear observational evidence for the growth of dust grains to sizes of a few cm at least.

A very brief introduction to the theory of line broadening is presented.

The discovery that the short-lived radionucleide 60Fe was present in the oldest meteorites suggests that the formation of the Earth closely followed the death of a massive star. I discuss three astrophysical origins: winds from an AGB star, injection of supernova ejecta into circumstellar disks, and induced star formation on the boundaries of HII regions. I show that the first two fail to match the solar system 60Fe abundance in the vast majority of star forming systems. The cores and pillars on the edges of HII regions are spectacular but rare sites of star formation and larger clumps with masses 103-4 M๏ at tens of parsec from a supernova are a more likely birth environment for our Sun. I also examine γ-ray observations of 60Fe decay and show that the Galactic background could account for the low end of the range of meteoritic measurements if the massive star formation rate was at least a factor of 2 higher 4.6 Gyr ago.

We demonstrate the eclipsing binary detection performance of the Gaia variability analysis and processing pipeline using Hipparcos data. The automated pipeline classifies 1 067 (0.9%) of the 118 204 Hipparcos sources as eclipsing binary candidates. The detection rate amounts to 89% (732 sources) in a subset of 819 visually confirmed eclipsing binaries, with the period correctly identified for 80% of them, and double or half periods obtained in 6% of the cases.

We explore the possibility that galaxy clusters or halos could besuited environments to host fermions like massive neutrinos in theirdegenerate state. Equilibrium density profiles for galaxy clustersand halos are calculated where the contribution of fermion particlesto an isotropic collisionless component is taken into account.Fermions are supposed to cluster in CDM protoclusters while theirphase space density is sufficient for not neglecting the Pauli'sexclusion principle.


In low-mass disks, turbulent torques are probably the most importantway of redistributing angular momentum. Here we present the theory ofturbulent accretion disks. We show the molecular viscosity is far toosmall to account for the evolutionary timescale of disks, and wedescribe how turbulence may result in enhanced transport of (angular)momentum. We then turn to the magnetorotational instability, whichthus far is the only mechanism that has been shown to initiate andsustain turbulence in disks. Finally, we present both the basis andthe structure of α disk models.

Chemodynamical disc galaxy simulations coupled with stellar populations synthesis models allow to build multi-wavelength images from numerical simulations, and then to follow their morphological evolution in colour and not only on the mass distribution. Using such technique, we present the evolution of several photometric observables, of the Tully-Fisher relation, as well as the evolution of disc structural parameters.

The technique of pupil densification bridges the gap existing betweenconventionnal optical astronomy observing techniques and opticalinterferometry: it indeed leads to the concept of hypertelescope: an instrument that can provide direct images at the focus of an interferometer.The hypertelescope is the open sesame for high dynamic imaging with aninterferometer: indeed, the elementary remapping of the pupil operated by adensifier not only maximizes the dynamic range and the signal to noise ratioof images but also makes the interferometer compatible with most existingcoronagraphic devices.Moreover, a careful discussion about field of view show that for a dilutedarray, the pupil densification preserves all the relevant high angular resolution information collected by the interferometer and therefore inducesno field loss.

Planck is designed to image the anisotropies of the Cosmic MicrowaveBackground (CMB) over the whole sky, with unprecedented sensitivity (ΔT/T ~ 2 × 10-6) and angular resolution (~5 arcmin). Planckwill provide a major source of information relevant to several cosmologicaland astrophysical issues, such as testing theories of the early universe andthe origin of cosmic structure. The ability to measure to high accuracy theangular power spectrum of the CMB fluctuations will allow the determination offundamental cosmological parameters with an uncertainty of order a fewpercent. In addition to the main cosmological goals of the mission, the Plancksky survey will be used to study in detail the very sources of emission which“contaminate” the signal due to the CMB. This will result in a wealth ofinformation on the properties of extragalactic sources, and on the dust andgas in our own galaxy. One specific notable result will be the measurement ofthe polarized emission from our own Galaxy. The ability of Planck to measurepolarization across a wide frequency range (30–350 GHz), with high precisionand accuracy, and over the whole sky, will provide unique insight into theproperties of the interstellar medium. An overview is presented of the Planckmission, its scientific objectives, the key elements of its technical design,and its current status.

The author discusses models of the Milky Way. An interpolation formula for the contribution of the exponential disc to the circular velocity is proposed.

We have analyzed the distributions of CO and temperature in a large suite of simulatedmolecular clouds, in order to help us understand how to interpret CO line emission fromreal molecular clouds. We find that most of the CO is located at densities over103cm-3 where the temperature is roughly 10–20 K independently ofthe mean density, metallicity and UV field strength. Although, most of the volume is inwarmer and thinner regions where CO abundance is small. On that account, CO observationsalone give a misleading view of the physical conditions in the clouds.

Energy, and more generally conserved charges, is a subtle issue in general relativity and it is subject to controversy. Indeed, there aremany different definitions in the literature and in some cases they do not all give the same charges. For example, as emphasized byGibbons, et al. (2005), not even in four dimensions do all authors obtain the same expression for the energy of Kerr-AdS black holes and some of these expressions are in disagreement with the first law of black hole thermodynamics. I adopted in [arXiv:0705.0484] the method formulated by Regge & Teitelboim (1974). Based on the Hamiltonian formulation of gravitation, it associates to each asymptotic Killing vector a conserved charge without having to make any arbitrary choice. The charge is then expressed as a surface integral over a 2-sphere at spatial infinity. I investigate here conserved charges and asymptotic symmetries in both asymptotically flat and AdS spaces in arbitrary spacetime dimensions. The study is presented in general coordinates, including the ellipsoidal coordinates that are well adapted to the Kerr solution.

I briefly review the role of atomic diffusion in various types of stars and describe some of the limits of current calculations. These suggest numerous directions for further work.

The cooling of baryons in the centers of dark matter halos leads to a more concentrated dark matter distribution. This effect has traditionally been calculated using the model of adiabatic contraction, which assumes spherical symmetry, while in hierarchical formation scenarios halos grow via multiple violent mergers. We test the adiabatic contraction model in high-resolution cosmological simulations and find that the dissipation of gas indeed increases the density of dark matter and steepens its radial profile compared to the case without cooling. Although the standard model systematically overpredicts the increase of dark matter density, a simple modification of the assumed invariant from M(r)r to $M(\bar{r})r$, where $\bar{r}$ is the orbit-averaged particle position, reproduces the simulated profiles within 10%.