Metal enrichment of intracluster medium (ICM) is reanalysed in the hierarchical galaxy formation scenario. In order to investigate metal abundances of $\alpha$ and iron-peak elements, we incorporate metal production processes by type Ia supernovae (SNe Ia) as well as type II supernovae (SNe II) into the GALFORM model of semi-analytic galaxy formation. We find that a top-heavy initial mass function (IMF) of stars with a power index $x\simeq 0.35$ for starburst is required under the constraint that the IMF for quiescent disc star formation is the Kennicutt IMF. Our model shows an only mild evolution of [Fe/H] as suggested by a recent observation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We approach the dynamics in proto-stellar systems via the two-body problem associated to an anisotropic Schwarzschild-type potential. On the basis of the natural symmetries of the characteristic vector field, and using variational methods (particularly the classical lower-semicontinuity method), we prove the existence of infinitely many families of symmetric periodic orbits.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

It was suggested by Terlevich & Melnick (1985) that many nuclei classified as Seyfert 2s could be associated with WR stars recently formed in a powerful starburst. Since then, the signature of WR stars has been claimed to be observed in several Seyfert 2s and LINERs. Gonçalves et al. (1999) have shown that a small number of Seyfert 2s have very weak [N II] 6548,6584 lines, suggesting that these objects could be partly ionized by WR stars. We have obtained high S/N spectra of such “Weak-[N II] Seyferts” to investigate if WR stars can be observed in galaxies without any other evidence for a starburst nebulosity. Amongst other findings, we have detected the presence of emission features such as Si II 5056,6347 and Ni II 7380. Other lines, such as [Ar VI] 4711,4740 and [Fe III]4658 are possibly present, mimicking the Bowen blend.

The detection of WR stars in AGN poses interesting questions concerning the link between nuclear activity and star formation, providing another angle to the study of the Starburst–AGN connection. However, one must be very careful in interpreting the available data; for the time being, the role played by WR stars in these AGN remains an open debate.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Recent progress of theories of eruptive flares (and CMEs) is reviewed within a framework of reconnection model with emphasis on development of basic idea and concept.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present observations of the dynamic evolution of photospheric magnetic elements in the G-band, magnetograms and Dopplergrams. The observations were obtained with the Swedish 1m Solar Telescope on La Palma at close to the diffraction limit of $0{\hbox{.\!\!^{\prime\prime}}}1$. In the most quiet regions we observe individual bright points in the G-band with corresponding magnetic signal in the magnetograms. Where the filling factor of the magnetic field is larger, the bright points interact when advected by the granular and super-granular flow-fields, flux sheets form and fragment. The plage region of the decaying active region is filled with more complex topologies like ribbon structures with darker interior and bright, knotted edges. These change into flower-like shape when small in extent and into micro-pores when the flux region is larger in extent. The magnetic elements in the plage region are associated with upflows with strong downflows in the immediate vicinity in the low-field region.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present spectroscopic observations of the peculiar system AM1003-435, which is composed of two strong interacting galaxies, and numerical simulations of the encounter between the galaxies, following the dynamical evolution of the stellar and gaseous components.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A new cosmological multidimensional hydrodynamic and N-body code based on an Adaptive Mesh Refinement scheme is described and tested. The hydro part is based on modern high-resolution shock-capturing techniques, whereas N-body approach is based on a Particle Mesh method. The code has been specifically designed for cosmological applications.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The temperature, velocity and magnetic field structures of solar atmosphere are extremely in-homogeneous under consideration on a small spatial scales. This fact is the reason of significant difficulties in the attempts of disambiguous interpretation of observations. Particularly informative for investigation of the complex polarized radiation formation processes in the dynamic solar atmosphere with a fine-structured organization of magnetic fields are the distributions across the solar disk of the amplitude asymmetry ($\delta a$) and area asymmetry ($\delta A$) of Stokes profiles, as well as of the strength ratios $R$ in different combinations of spectral lines. At this paper such information has been obtained using the Stokesmeter of the STOP telescope at the Sayan observatory. It was found that for some Fraunhofer lines the distribution of $R$ has an evident equatorial-polar asymmetry, which is difficult to explain yet. Additionally this paper presents some new results of the theoretical simulation (with different parameters of magnetic flux tubes models and of the medium in their neighborhood) of the center-to-limb variations of $\delta A$ on the example of the FeI $\lambda 525.02$ nm spectral line and of the $R = B_{525.02}/B_{524.70}$. The conclusion is made that a reasonably good agreement theory and experimental data can be achieved, for the time being, only for the central regions of the disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this paper we present the new possibilities of classical ground – based observations for the purpose of improving the proper motions of some HIPPARCOS stars. The coordinates of asteroids, comets and other objects are calculated mostly by using the relative method and presented in a relevant reference frame via nearby stars (at the moment of observation) which materialize that reference frame. To improve the proper motions of stars we can use the latitude/universal time variations of ground – based data. Here, the results of improved proper motions in declination of some HIPPARCOS stars are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We include gravity in a loss of equilibrium model for the initiation of coronal mass ejections (CMEs). We examine equilibria for both normal and inverse polarity and neglect the effects of current sheets. Although equilibria exist for normal polarities, in the absence of current sheets, the equilibria are unstable to horizontal perturbations. For the inverse polarity configuration, we find that gravity generally has a negligible effect if the magnetic field is strong ($>$50 G) but that it can have a significant effect if the magnetic field is weak. Specifically, if the characteristic magnetic field is less than about 6 G, no eruption occurs if the CME mass is on the order of 2 $\times 10^{16}$ gm.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

SHIBAHASHI: I would like to know how many unknowns – how many equations – you must solve for in the inversion procedure in your new magnetic Doppler imaging method?To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Magnetic helicity, which is a measure of magnetic flux linking, is widely believed to play a crucial role for the solar coronal energetic processes, e.g. heating, flares and eruptions. In this paper, we introduce the several new findings of magnetic helicity physics in the solar corona both from the observational and theoretical points of view. The new observations based on the vector magnetograms successfully revealed that the solar coronal activity is indeed related not only to the intensity of magnetic helicity injection from the photosphere, but also to the complexity in the structure of magnetic shear. In particular, we recently found through the advanced analyses of vector magnetogram data that steep reversal of magnetic shear may efficiently activate the liberation of free energy stored in the coronal magnetic field. Motivated by the results, we developed the large scale three-dimensional simulation to investigate the causal relationship between the magnetic helicity injection and the energy liberation in the solar corona. The simulations clearly demonstrated that the reversal of the magnetic shear in a magnetic arcade can cause the sudden onset of plasmoid eruption. The mechanism is able to be explained as a self-exciting process of multiple magnetic reconnections. Finally, we propose a new scenario for the triggering mechanism of eruptive flares, which is called the reversed-shear flare model.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A series of coronal magnetograms, related to the active region NOAA 9068 is derived using the effects of the quasi-transverse (QT-) propagation at microwaves. In the assumption that the product of the electron density $N$ and the scale of magnetic divergence $L_d$ is constant and equal to $10^{18}$ cm$^{-2}$, the sensitivity of the measurements peaks at $B(G) \approx 180 \, \lambda^{-4/3} (cm)$, where $\lambda$ is the observational wavelength. The radio maps of the Sun taken with the Solar Siberian Radio Telescope (SSRT) at $\lambda = 5.2$ cm were sampled and converted into the 2D coronal magnetograms supplying absolute values of the total magnetic vector $\vec B$ in the range 10-30 G. Each coronal magnetogram covers the portion of the microwave source in the active region affected by the QT-propagation conditions in the corona.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We form a sample of nearby single stars. Their masses are estimated on the basis of the mass-luminosity relation. Our aim is to specify a reasonable space limit, i.e. a heliocentric volume, as small as possible, but to contain a sufficient number of stars so that an application of statistical laws becomes possible. Among the quantities calculated by us a special attention is paid to the mean mass of a single star and, also, to the local value of Agekyan's factor.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from dynamical Monte Carlo simulations of dense star clusters near the Galactic center (GC). While these clusters spiral in toward the GC by dynamical friction, they could undergo core collapse and form an intermediate mass black hole (IMBH) by runaway collisions. Clusters can reach within a parsec of the GC where, following tidal disruption, they would inject many young stars still bound to the IMBH into the GC region. This scenario (Gerhard 2001; Hansen & Milosavljević 2003) provides a possible explanation for the youth paradox raised by recent IR observations (Ghez et al. 2003).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In the last few years, new instruments mounted at modern large telescopes, as well as satellite instruments, have given to us the possibility of obtaining observations of much higher quality than in the past. Yet, the large majority of observations of A-type stars are performed with small to middle size class telescopes. In this paper I discuss the scientific case for the use of large size class telescopes for the A-star research.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study the effects of radiative cooling, star formation and stellar feedback on the properties and evolution of galaxy clusters using high-resolution Adaptive Mesh Refinement N-body+gasdynamics simulations of clusters forming in the $\Lambda$CDM universe. Cooling leads to the condensation of gas in the inner regions of clusters, which in turn leads to steepening of the dark matter profile. The cooling gas is replaced by the higher-entropy gas from the outer regions, which raises the entropy and temperature of gas in the cluster core. The magnitude of these effects is likely overestimated in the current simulations because they suffer from the overcooling problem: a much larger fraction of baryons is in the form of cold gas and stars than is observed. We find that the thermal stellar feedback alone does not remedy this problem. Additional ad-hoc preheating can lower the amount of cold gas but a simple uniform preheating results in incorrect star formation history, as it delays the bulk of star formation until $z<1$. Our analysis shows that the overcooling in a cluster as a whole is really the overcooling in the central galaxy and its progenitors at high redshifts. This indicates that an additional heating mechanism that can continuously heat the gas in the cluster core is required to reproduce the observed cluster properties. Energy injection by the Active Galactic Nuclei, which may provide such heating, may thus be an important missing ingredient in the current theoretical models of cluster formation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Virtual Observatory (VO) will revolutionise the way we do Astronomy, by allowing easy access to all astronomical data and by making the handling and analysis of datasets at various locations across the globe much simpler and faster. I report here on the need for the VO and its status in Europe, including the first ever VO-based astronomical paper, and then give two specific applications of VO tools to open problems of A-stars research.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report on some of the recent work that has come from our Hubble Space Telescope programme to find massive black holes in nearby spiral galaxies. Determining black hole masses from gas kinematics in spiral galaxies is difficult, but results have been reported for NGC 4041 and new results are soon to be reported for NGC 1300 and NGC 2748. Complementary programmes are also looking for the presence of nuclear star clusters in our Space Telescope Imaging Spectrograph (STIS) and archival Near-infrared Camera and Multi-Object Spectrometer (NICMOS) images. We are also currently analysing United Kingdom Infrared Telescope (UKIRT) Fast Track Imager (UFTI) near-infrared images to determine the surface brightness profiles for 37 of the galaxies in the sample.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Equilibria and evolutions in the coronal magnetic configurations due to the interactions among active regions are investigated. The magnetic structure includes a current-carrying flux rope that is used to model the prominence or filament. We use either two dipoles or four monopoles on the boundary surface to model active regions, and the change in the boundary conditions corresponds to either the horizontal motion of magnetic sources or decaying of the active regions. Both cases show the catastrophic behavior in the system's evolutions. The results have important observational consequences: most eruptive prominences that give rise to CMEs are driven by the interactions between two or more active regions. Such eruptions may not necessarily take place in the growing phase of the active regions, instead they usually occur at the decay phase.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html