We use numerical simulations of galaxy clusters to study the dynamical and thermal evolution of the ICM from high redshift to the present time. We measure the properties of the satellites accreting on the cluster main progenitor and then measure their self-bound mass fraction as a function of time after the merging. We also calculate the mean properties of their orbits and investigate the time evolution of their internal velocity dispersion and gas temperature. We measure and model the mean pericentric and apocentric times, distances and velocities. Finally we show how the properties of the ICM at redshift zero can be understood by decomposing them as a function of the cluster merging history.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Fundamental information about the nature of solar filaments and governing physical processes are retained in their small-scale structure and dynamics. The paper reviews some recent high resolution studies of filaments, with emphasize on potential impact on current understanding of their physical nature.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from a set of high ($512^3$ effective resolution), and ultra-high ($1024^3)$ SPH adiabatic cosmological simulations of cluster formation aimed at studying the internal structure of the intracluster medium (ICM). We discuss the radial structure and scaling relations expected from purely gravitational collapse, and show that the choice of a particular halo model can have important consequences on the interpretation of observational data. The validity of the approximations of hydrostatic equilibrium and a polytropic equation of state are checked against results of our simulations. We also show the first results from an unprecedented large-scale simulation of 500 $h^{-1}$ Mpc and $2\times 512^3$ gas and dark matter particles. This experiment will make possible a detailed study of the large-scale distribution of clusters as a function of their X-ray properties.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Chemically peculiar stars are ideal astrophysical laboratories for furnishing a wide range of theoretical and observational aspects of our knowledge of the physical processes in stars. Recent dramatic improvements in the quality of the observational data and refinements of the modelling techniques led to an emergence of a new branch of stellar astrophysics which is focused on the reconstruction and the understanding of the origin of the three-dimensional structures in stellar surface layers. In this contribution I present an overview of recent results of the detailed modelling of the chemical nonuniformities, the magnetic and the pulsation velocity fields in the atmospheres of A stars. New Doppler imaging analyses of the magnetic field and the chemical inhomogeneities reveal an unexpected complexity of the surface formations and suggest that nonmagnetic phenomena play an important role in shaping the geometry of chemical spots. Consideration of the line profile shapes observed at high spectral and time resolution has made it possible to probe the radial dependence of the chemical abundances and the pulsation characteristics of cool pulsating Ap stars. An extension of Doppler mapping to the reconstruction of non-radial stellar oscillation structure delivers a solution of the long-standing problem of the pulsational geometry of roAp stars and helps to elucidate the interrelation between the pulsations, the magnetic field and the stellar rotation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

On 28 Oct 2003, one of the biggest flares (4B/X17.2) seen in recent years occurred in Active Region (AR) NOAA 10486 associated with a violent halo coronal mass ejection. It was a complex $\beta\gamma\delta$ region. After studying the evolution of the AR and the phenomena of this powerful flare, we obtained the following result. (1) Highly sheared transverse field was formed gradually on both sides of the neutral line by squeeze during the AR development; (2) Rotations of penumbra of main polarities were discerned, and the average horizontal velocities was as large as 0.55 km/s; (3) The spiral transverse field of main positive polarity was diffused after the large flare; (4) Some magnetic features submerged or emerged in the vicinity of the flare onset point. The emergence of this rotational and complex magnetic topology implies a transport of magnetic energy and complexity from the low atmosphere to the corona. Moreover, the rapidly submergence (emergence) and movements of the small magnetic features which represent the enhancement (cancellation) and squeeze of the magnetic field play a key role in the onset of the flare.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The results of a numerical simulation of the tidal evolution of the Earth-Moon system during the Phanerozoic epoch (the last 600 million years) are given. In most of the researches devoted to the solution of the problem the authors simplified and parametrized very complicated tidal phenomena to a primitive integral hump on the Earth's surface. As distinct from these the numerical model of the ocean tides in its most complete form is the core of the present study: the problem is solved for a viscous liquid in a paleoocean with variable outlines and depth allocations stimulated by the drift of the lithospheric platforms; the global interaction between the ocean and earth tides and the fluctuations of the gravitational field of the planet caused by them are taken into account. The astronomical component of the model is simplified. It is assumed that the Earth-Moon system is isolated, the Moon's orbit circular and the moment of inertia of the Earth constant during the Phanerozoic epoch. It is shown that the evolution of the Earth-Moon system during the Phanerozoic was nonuniform and that the primary role in this process belongs to the geodynamic factor.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a numerical code to synthesize the stellar population of galaxies, using the observed flux as observable, for the visible and IR range This code is an evolution of a previous one, which used the equivalent widths.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The sporadic solar radio emission of patrol solar radio observations within the periods 1980, 1984–1989 and of observations with high temporal and spectral resolution in 1989 are used to find the manifestation of pre CMEs activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this study we give a first description of De Haerdtl's 3:7 inequality between the Jovian satellites Ganymede and Callisto and 1:5 inequality between the Saturnian Titan and Iapetus and the resonant arguments associated. For each inequality, 19 arguments are associated. The overlapping of resonant zones induces stochasic layers that the system might have crossed in the past thanks to tidal dissipation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The chromosphere is an intriguing part of the Sun that has stubbornly resisted all attempts at a comprehensive description. Thus, observations carried out in different wavelength bands reveal very different, seemingly incompatible properties. Not surprisingly, a debate is raging between supporters of the classical picture of the chromosphere as a nearly plane parallel layer exhibiting a gentle temperature rise from the photosphere to the transition region and proponents of a highly dynamical atmosphere that includes extremely cool gas. New data are required in order settle this issue. Here a brief overview of the structure and dynamics of the solar chromosphere is given, with particular emphasis on the chromospheric structure of the quiet Sun. The structure of the magnetic field is also briefly discussed, although filaments and prominences are not considered. Besides the observations, contrasting models are also critically discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A comprehensive overview of the $\lambda$ Bootis stars is presented. This small group (only a maximum of 2% of all objects in the relevant spectral domain) are Population I late B to early F-type stars, with moderate to extreme (up to a factor 100) surface underabundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). They form a separate group among the classical chemically peculiar objects of the upper Main Sequence as their underabundances are quite outstanding. The basic membership criteria as well as the theories to explain the $\lambda$ Bootis phenomenon are covered. New observations including detailed elemental (surface) abundances, tests for pulsational instability, fluxes in the IR region, and measurements from the Hipparcos satellite permit one to make a statistical sound analysis of the group properties. Details of the evolutionary status, abundance pattern and tests for developed theories are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present simulation results about the interplay between super star clusters (SSCs) and the host dark-matter (DM) halo, with emphasis on the formation of bulges in very late-type galaxies. Simulations show that the NFW halo close to a stable state has no significant response to sinking of circumnuclear SSCs. Generally speaking, while the halo becomes hotter, its central cusp survives. The structures of the formed bulges are similar to what we obtained with fixed NFW halos, but the bulge formation fraction at various stages are smaller.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

To understand cluster formation and evolution it is important to understand the evolution of cluster substructure. The work described here focuses upon a set of fully self-consistent numerical simulations within a $\Lambda$CDM cosmology. Within the simulations we follow in detail the temporal and spatial properties of individually tracked satellite galaxies. The host galaxy clusters were chosen to sample a variety of formation histories, ages, and triaxialities. Despite their obvious differences, we find striking similarities within the associated substructure populations. Namely, the satellite galaxy orbital distributions are indistinguishable between the galaxy clusters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The results of solar microwave observations in the Radio Astronomical Observatory NIRFI “Zimenki” are examined. Data analysis shows the presence of periodic component, that arose prior to burst connected to CMEs onset, and its absence after burst. Obtained data are compared with the dynamics of the development of activity on the solar disk. Results can be considered as the illustration of the dynamics of wave motions in the periods of flare activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In view of the possibility of employing Cassini's experiments for the diagnosis of the Saturnian ring system, local $N$-body simulations of low and moderately high optical depth regions of Saturn's main rings are presented. A special emphasis is made on fine-scale spiral structures (irregular cylindric wave-type structures of the order of 100 m or so) of Saturn's A, B, and C rings. It is predicted that Cassini spacecraft high-resolution images of Saturn's rings will reveal this kind of small-scale irregular density wave structure.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present first results of numerical simulations of the dynamics of all three components of a galaxy cluster: the dark matter, the intracluster gas, and the member galaxies. Our first aim is to understand the enrichment of the gas component by studying various interaction processes between cluster galaxies and the intracluster gas, notably ram-pressure stripping and galactic winds. Our second aim is to find out how fast metals originating from such interaction processes diffuse throughtout the cluster, in order to understand observed metallicity maps of galaxy clusters obtained from X-ray observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have developed the technique and software to observe and process spectral data obtained with the CCD camera. It makes possible to construct two-dimensional maps of Doppler velocity and intensity in solar features simultaneously at two levels in the solar atmosphere. We present some results derived from study of the structure and space-time variations of the Doppler velocity in the region of quiescent filaments in the chromosphere (the $H_{\beta}$$\lambda 486.1$ nm line) and under filaments in the photosphere (the Fe I $\lambda$ 486.3 nm. and Fe I $\lambda$ 485.9 nm lines). We came to a conclusion that motions in quiescent filaments consist of both the stationary and oscillatory components and follow helical trajectories.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Two topics concerning A-type stars are discussed: starspots associated with the strong magnetic fields and the prospects for asteroseismology. Considering starspots as analogous to sunspots is misleading. The photosphere of starspots of a magnetic A-star is higher than the normal photosphere, contrary to sunspots. As for the prospects of asteroseismology, it is demonstrated how well (or poorly) we can probe the internal structure of the distant stars using a limited number of p-mode frequencies. Although the detectable eigenmodes must be limited to be $\ell \leq 4$, if the observational error is of the order of $10^{-3}$, inversion has still some hope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a new method to decompose the stellar population mixtures in galaxies. The method combines the spectra of simple stellar populations (SSP) of different ages and metallicities, computed with the recently published high spectral resolution evolutionary synthesis models of Bruzual & Charlot (2003). Statistical mechanics techniques, based on Markov Chain Monte Carlo methods, are used in the search for the combination of SSPs which best matches an observed spectrum. The spectral base covers 10 ages and 3 metallicities. The method provides the Star Formation History (SFH) expressed in a population vector $\vec{x}$, whose components represent the fractional contribution of each SSP to the total flux (or mass). The code also estimates the velocity dispersion σ[sstarf ]. A series of simulations were performed to evaluate the code's ability to recover the input parameters (SFH, extinction and velocity dispersion), to investigate the effects of noise in the data and map intrinsic degeneracies of stellar populations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Asteroseismology may help detect diffusion-induced helium gradients inside Main-Sequence A stars. Models have been computed for 1.6 and 2.0 $M_{\odot}$ stars with pure helium diffusion, at different ages, so that the helium gradient lies at different depths inside the star. The adiabatic oscillation frequencies have been analysed and compared with those of a model without diffusion. Clear signatures of the diffusion-induced helium gradient are found in the so-called “second differences”. These frequency differences present modulations due to the partial reflection of the sound waves in the layer where the helium gradient occurs. A tentative application to the roAp star HD 60435 is presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html