We estimate the gas mass fractions for a sample of 39 high-$z$ galaxy clusters using a combination of three different data sets: Chandra X-ray data, OVRO/BIMA centimeter-wave Sunyaev-Zel'dovich Effect (SZE) data, and published weak gravitational lensing data. The gas mass fraction $f_g$ is calculated in three different ways. The X-ray surface brightness and SZE decrement are used independently to determine the number of baryons in the intracluster gas and subsequently the gas mass; the total mass follows assuming spherical symmetry and hydrostatic equilibrium (HSE). The third, less model-dependent approach is to calculate the projected SZE gas mass along a cylinder and divide by the total mass derived from the lensing data. The goal of this study is to compare the $f_g$ results from the three different methods to investigate systematic uncertainties associated with clumping of the intracluster medium, cluster elongation, and the HSE assumption.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Based on Nançay Radioheliograph (NRH) observations, we have identified 4 Type I noise storm continua sources associated with the Bastille Day flare/CME event. Two of them were stable and closed to active regions. Their outskirts covered AR9077 and 9082, respectively. One source was over the south-west limb and in the high corona, it was stable for hours. All the Type I storm sources weren't observed simultaneously before 10:20 UT at the onset of the global CME, which indicated the intrinsic association of Type I noise storm and CME initiation. The wide span of the Type I storm sources and burst sources clearly implied that the Bastille Day flare/CME involves large or even global magnetic interaction.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The change in the measured position due to the chromatic effect in the optical system is usually so small that it can be neglected. However, in the case of the Hipparcos mission, this effect is of the same magnitude as the targeted precision; it is therefore mandatory to correct for it. The different assumptions adopted to build up such corrections in the Hipparcos framework are presented. Some of their limitations and how they can be overcome to improve the results even today are described. The chromaticity mainly affects red stars and has its strongest impact on the astrometry of very red and highly variable stars such as Miras. Nevertheless, the implications on distance scale determination are rather small.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper explores the advantages of using gravity assisted trajectories to perform flyby and rendezvous missions to accessible near-Earth asteroids (NEAs), in terms of the total velocity budget required for the mission. Combining the Opik's formalism of close encounters with the Monte Carlo sampling technique and Lambert trajectories, we give a general picture of the accessibility regions for NEAs in phase space of orbital elements, without considering the phasing requirements between bodies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

BAGNULO: I would like to ask Mathys and Moss to comment about the possible detection of the radial gradients of the magnetic .elds in Ap stars. What would be the consequence of such a feature on the stellar atmosphere? I refer in particular to that the length scale for horizontal variability of the field is not less than 105 km, whereas the depth of the photosphere may be 100 times less.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A total of 266 type III bursts observed with the 2.6 - 3.8 GHz high temporal resolution dynamic spectrometer of NAOC during the 23rd solar cycle (from April in 1998 to January in 2003) are statistically analyzed in this present paper. The frequency drift rates (normal and reverse slop), durations, polarizations, bandwidth, starting and ending frequencies are analyzed in detail. From the statistical results of starting and ending frequencies we show that the regions of starting frequencies are very large, which are from less than 2.6 GHz to greater than 3.8 GHz; but the ending frequencies regions are relative concentration, which are from 2.82 GHz to 3.76 GHz. These phenomena mean that the sites of electrons acceleration are quite scatter, while the cutoff regions of the radio type III bursts are in the limiting domain. The bursts number with positive and negative drift rates are nearly equal. This correlation may interpret the suggest that a proportional number of electron beams in the directions of upward and downward are accelerated in the range of 2.6 - 3.8 GHz. The other statistical results are similar to those of decimetric type III bursts as statistics in previous literature. The emission mechanisms of microwave type III bursts are mainly caused by the plasma radiation and electron gyro-maser radiation.

From the statistics of microwave type III bursts and associated coronal mass ejections (CMEs), it is found that the 36% of type III bursts (97) are corresponding to the CMEs for occurring time and site. The correlation between the type III bursts and CMEs is not close, and most type III bursts are occurred in the time regions of 26 – 30 minutes before CMEs. This means that the partial microwave type III bursts may be a precursor of the CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Eclipsing binary light curves have provided the ‘royal road’ (Russell 1948) to fundamental astrophysical information on stars. If radial velocities of the components and a reliable colour/temperature/flux relation are available, parallaxes may be determined and compared with direct measures, e.g. by Hipparcos. Accuracies of existing measures are considered and aspects of the development of this and other methods of distance determination reviewed. Roles for multiwavelength techniques (e.g. VLBA, broad-spectrum photometry) are noted. The recovery of information on new planets orbiting remote stars by transit phenomena will be looked into within this context.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An increasing number of AGNs exhibit broad, double-peaked Balmer emission lines, which arise from the outer regions of the accretion disk which fuels the AGN. The line profiles vary on timescales of 5–10 years. Our group has monitored a set of 20 double-peaked emitters for the past 8 years (longer for some objects). Here we describe a project to characterize the variability patterns of the double-peaked Hα line profiles and compare with those of two simple models: a circular disk with a spiral arm and an elliptical disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Present day estimates of the Hubble constant based on Cepheids and on the cosmic microwave background radiation are uncertain by roughly 10% (on the conservative assumption that the universe may not be perfectly flat). Gravitational lens time delay measurements can produce estimates that are less uncertain, but only if a variety of major difficulties are overcome. These include a paucity of constraints on the lensing potential, the degeneracies associated with mass sheets and the central concentration of the lensing galaxy, multiple lenses, microlensing by stars, and the small variability amplitude typical of most quasars. To date only one lens meets all of these challenges. Several suffer only from the central concentration degeneracy, which may be lifted if one is willing to assume that systems with time delays are either like better constrained systems with non-variable sources, or alternatively, like nearby galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The KLENOT project is a project of the Klet Observatory, Czech Republic, devoted to astrometric observations of Near-Earth objects, distant objects and comets. The improved effort of the large NEO surveys resulting in an increasing number of newly discovered NEOs calls for continuous follow-up astrometry to secure an accurate orbit determination of discovered bodies first in discovery opposition and then during next apparitions. Considering this urgent need of astrometric follow-up, the fact that many of these targets are fainter then magnitude 20.0 V and our results and experience in minor planet and comet CCD astrometry done at Klet since 1993, we decided to bring into operation a new 1-m class facility working on a permanent basis - the KLENOT telescope. The regular observing of the telescope started in March 2002 (the MPC code 246). Beside methods and techniques we use for follow-up astrometry we present most important results of the project.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have digitized and processed the daily K-CaII-line full disk spectroheliograms from the archive of the Kodaikanal Observatory during 1907-1995. The programm has been worked out to determine the boundaries of the bright areas (plages, decayed plages, enhanced network features, K-CaII bright points and so on) with contrast that exceeded a level of the quiet Sun on the given value. About the $1.2\,{\times}\,10^6$ K-CaII active regions of different scales were processed. The coordinates, areas, the tilt and latitude-time distributions of bright features were determined. At the high latitudes the K-CaII bright points form a polar branch of solar activity at the period between the polar magnetic field reversals. This polar activity shows both 11-year's and 22-year's cycles. We found that the polar K-CaII bright point cycles proceed on average 5.5 years the sunspot cycles.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The last decade has seen an explosion in the number and scope of wide-field surveys. The data provided by these surveys will greatly increase our understanding of the relationships between the outskirts and the cluster centers and the field. I summarize the status of current deep-wide optical surveys and describe the plans for the next generations of surveys, with particular emphasis on the applications of these surveys to weak gravitational lensing. As a concrete example of such a survey, I will present results from the Deep Lens Survey (DLS).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By fitting to the quiescent galaxy MBH−σ∗ relation, we calculate the average shift required to scale reverberation-mapped AGN masses to the same zero-point. We use reanalyzed virial products (rV2/G) and both new and published velocity dispersions to find the offset in the AGN calibration. This scaling factor, 〈f〉, accounts for the detailed dynamics and geometry of the broad-line region (BLR). Finally, we confirm the rough correlation between σ∗ and FWHM([O III]) for these 16 AGNs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Galaxy clusters at $z\sim1$ are particularly important in the study of cluster evolution and the application of clusters to cosmological studies. We briefly discuss the difficulties in creating well-defined, large, high-redshift cluster samples, and some of the techniques used in optical/IR imaging to overcome them. We give a summary of the current state of optical/IR observations of the relatively small number of high-redshift clusters identified so far, including discussions of the galaxy luminosity function, the Fundamental Plane, the color-magnitude relation, and the Butcher-Oemler effect. The application of photometric redshift techniques is also highlighted.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Here we analyse the solar cycle (SC) 23 behavior and we also make a comparison with some previous cycles and present a few aspects concerning the forecasts made for SC 23 maximum. As regards the following cycle, in accordance to other early predictions, our empirical method, based on observing the flare energy release during the descendant phase of the precedent SC, estimate that the amplitude of SC 24 will be low.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Recent years have seen a revolution in the possibility to understand cometary capture, i.e., the origin of the cometary population that moves in orbits confined to the inner Solar System. This is due to the discovery of the major source populations: the Edgeworth-Kuiper belt, and the scattered disk. We review the current understanding of the links between the distant sources, including the Oort cloud, and the observed, short-period population, and the problems that remain. Some highlights of present research in this field will serve to illustrate recent progress and major issues that are currently arising.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Very long baseline interferometry (VLBI) is a radio astronomy technique that allows imaging and astrometry at milliarcsecond or better resolution. The last decade has seen improvements in VLBI techniques and equipment which have enabled precision astrometry of pulsars. Most notably, VLBI arrays have become more sensitive and calibration has become more accurate. Pulsar astrometry using VLBI can readily yield a proper motion and in many cases a trigonometric parallax as well. These observables have have numerous applications which justify the difficulty of the measurements. The goals of pulsar astrometry include: 1. determination of the distribution of pulsar birth velocities, a critical probe of supernova asymmetry; 2. improvement in understanding of the ISM through observations of pulsar bow shocks, interstellar scattering, and timing dispersion measures; and 3. understanding characteristics of individual pulsars though knowledge of their distance and velocity. I will discuss these science cases, some recent results, and prospects for better astrometry in the near future.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe a new project aiming at measuring time delays for most known lensed quasars, from optical light curves obtained with five (almost) dedicated 1-2 m telescopes in the Northern and Southern hemispheres. The goal is to evaluate the Hubble constant H$_0$ with a precision below 2%. We present here numerical simulations in order to define the optimal temporal sampling in our observations as a function of typical quasar variations, object visibility, and for a given accuracy on the individual photometric points. It is also emphasized that the ongoing effort to obtain deep imaging using both space and ground based facilities must be continued, as illustrated by the comparison of HST and VLT near-IR images of the “cloverleaf”: H 1413+117.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We briefly review the traditional classifications of CP stars. The current availability of large numbers of abundances now make it possible to use multivariate techniques, both to supplement traditional classification methods and probe the abundance patterns. We discuss cluster analysis and correlation matrices for sample material. We review the historical resistance to the notion that CP stars were indeed chemically peculiar. Modern work shows that while these objects do indeed have atmospheric anomalies, they are nevertheless chemically peculiar.

Abundance patterns are an important clue to the origin of the abundance peculiarities. We contrast patterns due to nuclear and chemical differentiation processes. The roAp and related stars show vertical as well as horizontal abundance variations, and abnormal line profiles. Photospheric abundances in these stars are surely abnormal (nonsolar), but as long as the models are uncertain the derived abundances will be very crude.

For more than two decades, observations of CP stars in the X-ray and radio regimes have been made with increasing sensitivity and pointing accuracy. We discuss the current evidence linking magnetic and nonmagnetic CP stars to sources of galactic X-rays and radio radiation. There seems no doubt that high energy phenomena are associated with, if not produced by, some CP stars. This circumstance admits the possibility that the release of high energy particles (p's, n's and $\alpha$'s) during such events may initiate nuclear reactions on the surfaces of the CP stars. We briefly reconsider the viability of such processes for producing exotic species like Pm by proton bombardment using recent data for solar and stellar flares.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Although we are on the descending branch of solar cycle 23, a very strong active region, NOAA 652, crossed the solar visible hemisphere during the second half of July 2004. Its very large sunspot was of beta- gamma- delta type. This active region was a source of numerous X-ray flares and coronal mass ejections. Being in a favorable position not far from the equator, it represented a threat to planet Earth particularly when near its central meridian passage.

Using EIT images, it was possible to locate the position of the 2004 July 25 CME ejection as dimming of several loops to the SW of AR 652. As usual, the CME lift up was accompanied by type IV burst and followed by type II burst and a proton flare.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html