The statistics of giant arc formation by galaxy clusters has long held promise as a cosmological tool. Progress in this field relies upon advances in modeling, and in observational samples. We introduce several new lens samples from the Red-Sequence Cluster Survey (RCS-1) which provide a significant increase in the total sample of clusters with arcs, while adding several new observational puzzles. The most significant of these observations is that the redshift distribution of clusters which form arcs is unexpectedly skewed to higher redshifts. We also discuss upcoming samples from the ongoing RCS-2 survey and other planned surveys; preliminary results from RCS-2 support this unexpected redshift distribution and deepen the disagreement between theory and observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In order to explain the different average speeds between halo and limb CMEs, we investigate the relationship between the brightness and speed for 17 halo CMEs. It is found that faster CMEs tend to be brighter, which implies that many halo CMEs with slow speeds are missed in observation owing to the limited sensitivity of LASCO detectors or identifications. As a result, the statistical average speed of halo CMEs turns to be much larger than that of limb CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Radiation hydrodynamics simulations have been used to produce numerical models of the convective surface layers of a number of stars, including the Sun and other stars on or above the main-sequence, white dwarfs of type DA, and red supergiants.

While granulation of main-sequence solar-type stars resembles that of the Sun, the convective velocity fields of F-type stars are much more violent and accompanied by strong pulsations. The properties of the thin convection zone(s) of A-type stars differ again (see Fig. 1). In this contribution, the pattern and dynamics of their surface granulation, the photospheric velocity fields and their effect on line profiles are investigated, based on new 3-D models of surface convection in main-sequence A-type stars with $T_{\rm eff}$=8500 K and 8000 K. Furthermore, we will look below the surface to study overshoot and the interaction of the surface convection zone and the deeper helium II convection zone.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We identify the dominant emission processes in 3C 270 in the infrared to be non-thermal, and emission from its dusty disk does not contribute significantly to the total infrared output. This implies that such disks can be hard to find through their infrared emission, and that any circumnuclear torus, if at all present, is small and thin.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

It is possible that narrow-line Seyfert 1 galaxies (NLS1s) are in the early stage of active galactic nuclei (AGNs) evolution. It is important to estimate the mass of supermassive black hole (SBH) in NLS1s. Here we considered the different kinds of methods to estimate the SBH masses in NLS1s. The virial mass from the Hβ linewidth assuming random orbits of broad line regions (BLRs) is consistent with that from the statured soft X-ray luminosity, which showed that most of NLS1s are in the super-Eddington accretion state. The mass from the [O III] linewidth is systematically larger than that from above two methods. It is necessary to measure he bulge stellar dispersion and/or bulge luminosity in NLS1s.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of 3–D nonlinear simulations of magnetic dynamo action by core convection within A-type stars of 2 $M_{\odot}$ with a range of rotation rates. We consider the inner 30% by radius of such stars, with the spherical domain thereby encompassing the convective core and a portion of the surrounding radiative envelope. The compressible Navier-Stokes equations, subject to the anelastic approximation, are solved to examine highly nonlinear flows that span multiple scale heights, exhibit intricate time dependence, and admit magnetic dynamo action. Small initial seed magnetic fields are found to be amplified greatly by the convective and zonal flows. The central columns of strikingly slow rotation found in some of our progenitor hydrodynamic simulations continue to be realized in some simulations to a lesser degree, with such differential rotation arising from the redistribution of angular momentum by the nonlinear convection and magnetic fields. We assess the properties of the magnetic fields thus generated, the extent of the convective penetration, the magnitude of the differential rotation, and the excitation of gravity waves within the radiative envelope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A revolution is taking place in the research of extra-solar planets with the discovery of the first exoplanets only a decade ago to the more than 100 systems known to date. Almost all of these extrasolar planets have been discovered using the radial velocity technique. Unfortunately, this limits the amount of information which can be obtain from these systems, with a $\sin i$ ambiguity in the planet's mass, and no further measurements of fundamental parameters as long as these planets can not be detected directly. This situation is very different in the rare case that the orbit of a planet has an inclination such that it occults its host star, as in the case of HD 209458b. Not only can the mass and radius of the planet be accurately determined, but it makes the system also suitable for many detailed follow-up studies, in particular atmospheric transmission spectroscopy. This has resulted in the detection of the atmosphere of HD 209458b in Sodium, and the discovery of an evaporating exosphere in Hydrogen, Carbon and Oxygen using the Hubble Space Telescope. In this paper I briefly review transiting exoplanets and methods to probe their atmospheres, with the emphasis on a new method of transmission spectroscopy making use of the Rossiter effect, which may be more suitable for the large ground-based telescopes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results of our wide-field redshift survey of galaxies in a 285 square degree region of the Shapley Supercluster (SSC).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Radio emissions from the solar active regions can be generated by nonlinear coupling of Langmuir waves with Alfvén waves. Multi-wavelength observations can be used to provide evidence for Langmuir-Alfvén turbulence in the solar atmosphere.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The degree of polarization of Compton-scattered photospheric light observed in a coronagraph is dependent on the distance of the scattering electrons from the plane of the sky. Measurements of the polarization of light scattered by CME structures have been observed by LASCO C2. We have reduced and analyzed a month long sequence of such measurements which were taken at a cadence of 1 hour. The CME brightness has been distributed throughout a 3 dimensional cube and visualized at a variety of angles. Several CMEs are found to have considerable fine-structure consistent with expanding loop arcades. The analysis is subject to a variety of assumptions such as a lack of knowledge of whether a source is before or behind the plane of the sky. Nevertheless, the results obtained to date are intriguing.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Weak gravitational lensing is considered to be one of the most powerful tools to study the mass and the mass distribution of galaxy clusters. However, the mass-sheet degeneracy transformation has limited its success. We present a novel method for a cluster mass reconstruction, which combines weak and strong lensing information on common scales and can as a consequence break the mass-sheet degeneracy. We extend the weak lensing formalism to the inner parts of the cluster, use redshift information of background sources and combine these with the constraints from multiple image systems. We apply the method to N-body simulations as well as to strong and weak lensing ground-based multi-colour data of RX J1347–1145, the most X-ray luminous cluster known to date. If the redshift measurements of background sources (for strong and weak lensing) and the identification of the multiple-image system are correct, we estimate the enclosed cluster mass within $360\: {\rm h}^{-1}\mbox{kpc}$ to $M(<360\: {\rm h}^{-1}\mbox{kpc})= (1.2 \pm 0.3) \times 10^{15} M_{\odot}$. With higher resolution (e.g. HST) imaging data, reliable multiple imaging information could be obtained and the reconstruction further improved.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In the beginning we review briefly the evolution of the ideas on the motion of the bodies in our solar system, from Newton's clockwork Universe to the presently accepted ubiquity of chaotic transport in the asteroid belt. Then we discuss the result of chaotic motion, which is transport in phase space, and we introduce the concept of diffusion of an asteroid in action space. We proceed by reviewing recent work on numerical as well as analytical study of asteroids following chaotic trajectories and we summarize the main results. We present several applications of the theoretical modelling of asteroid motion as diffusion in action space, to problems of specific interest.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

There is a tight M−σ relation in nearby inactive galaxies. Nearby radio-quiet AGNs also followed this relation. In order to investigate whether radio-loud AGNs and NLS1s follow this relation or not, we estimated their central black hole masses from Hβ and the bulge velocity dispersions from [O III] linewidth. We found that radio-loud AGNs and NLS1s seemed to deviate from this relation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The warm-hot intergalactic medium contains a major part of all baryons in the universe. Despite this, it is very hard to observe in X-rays due to its relatively low temperature and the poor spectral resolution of most instruments. The high sensitivity and good spectral resolution of XMM-Newton allowed for the first time to show the presence of the warm-hot intergalactic medium in the outskirts of several nearby clusters of galaxies. In this contribution these results are presented. The physical state of the gas such as temperature, density, mass and chemical composition are discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Yarkovsky effect (YE), a tiny nongravitational force due to radiative recoil of the anisotropic thermal emission, is known to secularly affect the orbital semimajor axis. Therefore, angular phases such as longitude in orbit or proper longitude of node undergo a quadratic perturbation. This is fast enough to allow direct detection of the YE. The first positive case was obtained for (6489) Golevka in 2003 and prospects are very good for many more detections in the near future. To make productive scientific use of the YE detections, we need to accurately compute its strength for a given body. Simple models, available so far, will likely not be adequate in many of the forthcoming YE detection possibilities. We thus developed a complex numerical approach capable of treating most of them. Here we illustrate its power by discussing the cases of: (i) Toutatis, with a tumbling (non-principal-axis) rotation state, and (ii) 2000 DP107, a binary system.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The accomplishments of space flights and introduction of new astrometric methods (radar ranging, lunar laser-ranging, VLBI measurements) in the 1960s required considerably more precise planetary ephemerides than it was possible with classical analytical theories by Leverrier, Hill, Newcomb and Clemence. On the other hand, these modern data made possible the creation of such ephemerides. Two series of numerical ephemerides of planets most complete up to now, and of the same level of accuracy, are considered in this paper. There are the well-known numerical DE ephemerides of JPL as well as the EPM (Ephemerides of Planets and the Moon) ephemerides produced at the Institute of Applied Astronomy. The description of the dynamical models, the brief characteristics of DE118, DE200, DE403, DE405, DE410, EPM87, EPM98, EPM2000, EPM2004 ephemerides, and the comparison between DE410 and EPM2004 are given. The latest DE410 and EPM2004 ephemerides have resulted from a least squares adjustment to observational data totaling about 300000 position observations (1911–2003) of different types. The accurate radar observations of planets and spacecraft have made it possible not only to improve the orbital elements of planets but to determine a broad set of astronomical constants from the value of the astronomical unit (AU) to parameters of PPN formalism. Recent estimates of different astronomical constant are presented, and progress is shown in the improvement of the AU value, the parameters $\beta, \gamma $, as well as possible variability of the gravitational constant $G$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

I present recent observations from two Hubble Space Telescope(HST)/ACS programs that target the most X–ray luminous and thus (presumably) most massive galaxy clusters at $z{=}0.5$ – the highest redshift at which complete, well–defined samples of such rare systems are available. The first program (GO:9836, PI: R.S. Ellis) exploits a huge mosaic of 41 ACS pointings spanning a 10 Mpc region centered on MS0451-03. This is the largest contiguous space–based image of a cluster to date. I describe a preliminary weak–lensing analysis and a new Keck/DEIMOS redshift catalog of 1000 galaxies in this field. The second program (GO:9722, PI: H. Ebeling) studies the core regions of the twelve most luminous clusters at $z{\ge}0.5$ from the MAssive Cluster Survey (MACS; Ebeling et al. 2001). Multi–color ACS observations in combination with recent Keck/LRIS spectroscopy of gravitational arcs constrain the distribution of mass in the cluster cores, thus laying the foundation for detailed multi–diagnostic (lensing, X–ray, near–infrared, SZE) investigation of this sample. For example, it is of particular interest to explore how the structure and state of relaxation of massive clusters evolved between this sample at $z{\ge}0.5$ that measured by Smith et al. (2004, astro–ph/0403588) at $z{=}0.2$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The convection code of Nordlund & Stein has been used to evaluate the 3D, radiation-coupled convection in a stellar atmosphere with $T_{\rm eff} = 7300$K, log $g = 4.3$ and $[{\rm Fe}/{\rm H}]= 0.0$, corresponding to a main-sequence A9 star. I present preliminary comparisons between the 3D-simulation and a conventional 1D stellar structure calculation, and elaborate on the consequences of the differences.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In order to verify scenario of solar cycle suggested by Babcock and Leighton, a new index of activity is derived from observational data of bipolar spot groups by taking positions of magnetic poles of the groups into account. In agreement with the Babcock-Leighton scenario, this index reveals substantial correlation with amplitude of the axisymmetric magnetic field of the Sun measured at subsequent minimum of activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the eruption of a small $H_{\alpha}$ filament and associated partial halo coronal mass ejection (CME) occurring in NOAA AR 9616. Accompanied by a M1.5 flare, the filament quickly erupted, a remote coronal dimming region far away from the eruption site was formed above quiet-sun area, and then a long $H_{\alpha}$ surge developed from the flare site. During the eruption, remote $H_{\alpha}$ and EUV brightenings appeared near the dimming, along the dimming boundary in EUV and in its interior in $H_{\alpha}$, leaving behind EUV loops connecting the eruption source region and the remote EUV brightenings. Finnally, as a definite indication of the CME, a huge dark loop appeared to span the eruption region. These observations indicate that a much larger-scale rearrangement of the corona magnetic fields, eventually represented by the CME, was involved in the eruption of the small filament.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html