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The optical design for the proposed Euro50 extremely large telescopewith integrated adaptive optics (AO) is presented. For atmosphericturbulence correction, we propose using single and dual-conjugate AOsystems working with natural and laser guide stars. The corrective shapeof the deformable mirrors (DMs) is derived from an analytical algorithmbased on minimization of the sum of the residual power

Gaia is ESA’s ambitious space astrometry mission with a foreseen launch date in early 2012. Its main objective is to perform a stellar census of the 1000 Million brightest objects in our galaxy (completeness to V=20 mag) from which an astrometric catalog of micro-arcsec level accuracy will be constructed. A key element in this endeavor is the Astrometric Global Iterative Solution (AGIS) - the math

We present a new study of deep star counts in the Local Group dwarf spheroidal (dSph) in Ursa Minor. Both the luminosity function (LF) and the color-magnitude diagram (CMD) of the unevolved stars are compared with the LF and CMD of the old, metal-poor globular cluster M92. The main sequence locations and turn-offs are identical within the errors. Since we. know from the brighter evolved stars that

The expected distributions of eclipse-depth versus period for eclipsing binaries of different luminosities are derived from large-scale population synthesis experiments. Using the rapid Hurley et al. BSE binary evolution code, we have evolved several hundred million binaries, starting from various simple input distributions of masses and orbit-sizes. Eclipse probabilities and predicted distributio

We discuss mass transfer in eccentric binaries containing a white dwarf and a neutron star (WD-NS binaries). We show that such binaries are produced from field binaries following a series of mass transfer episodes that allow the white dwarf to form before the neutron star. We predict the orbital properties of binaries similar to the observed WD-NS binary J1141+6545, and show that they will undergo

ESA's Gaia mission will provide accurate astrometric, photometric andspectroscopic data for millions of stars in the Galaxy and beyond. Wediscuss the prospects of using this vast amount of astrophysicalinformation for understanding star formation histories in the Galaxy andits immediate neighbors within the Local Group.

Book abstract: The book reviews recent observations of non-evolved and evolved binary populations in clusters and the field with special emphasis on statistical biases, incompleteness and distribution functions. Different binary types are considered: cataclysmic variables, super-soft X-ray sources, double degenerate binaries, Algol-type binaries, Be binaries, X-ray binaries, and Wolf-Rayet binarie

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Dynamics of spontaneous decay and corresponding emission spectrum areexactly treated for a system of two identical two-level atoms in 1D.Just a one-dimensional case is considered in order to maximally extractan information on mutual influence of spatially remote atoms through theradiation field. As a result, an effect is revealed and considered indetail that there exist stable (metastable) entangl

We investigate the structure and evolution of blue straggler stars, which were formed from direct stellar collisions between main-sequence stars in globular clusters. In particular, we look at the rotational evolution of the products of off-axis collisions. As found in previous work, such blue stragglers initially have too high an angular momentum to contract down to the main sequence. We consider

The globular cluster M15 was observed on three occasions with the High Resolution Camera on- board Chandra in 2001 in order to investigate the X- ray source population in the cluster centre. After subtraction of the two bright central sources, four faint sources were identified within 50 arcsec of the core. One of these sources is probably the planetary nebula K648, making this the first positive