A systematic study of 30 Radio Loud AGNs available in the BeppoSAX archive has been carried out. The sample consists of 9 Broad Line radio Galaxies, 5 Steep Spectrum Radio Quasars and 16 Flat Spectrum Radio Quasars. These objects represent, according to Unified Models, objects with decreasing viewing angles. Our analysis shows considerable differences between FSRQs and BLRGs'SSRQS. As expected in the AGN Unified Model: i) the X-Ray spectrum of FSRQs is a simple power law with a hard spectral slope (the only exception being 3C273), ii) Broad Line and Steep Radio Spectrum AGNs show a steeper X-Ray continuum and Seyfert like features. We also find that the Fe line is weaker than in radio quiet objects. However no strong evidence emerges that a jet contamination may be the main responsible for the EW shrinking in BLRGs and SSRQs. Recent XMM-Newton observations of Pictor A, 3C445 and PKS 2152-69 confirm the nuclear BeppoSAX results and better constrain the Fe line parameters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A complex solar radio burst was observed on 19 October 2001 with the spectrometers of NAOC (National Astronomical Observatory of China) and Nobeyama Radioheliograph (NoRH). Basing on the analysis of brightness temperature spectra of radio sources and various fine spectral structures, we get a diagnosis of magnetic field of radio active region.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We show the utility of the Systematic Ranging technique by analyzing the orbit determination of asteroid 2004 FU$_{162}$, which passed approximately 6400 km from the surface of the Earth on March 31, 2004. The limited observations introduce strong nonlinearities that must be accounted for when estimating the actual encounter distance.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study the dark matter halos of galaxies with galaxy-galaxy lensing using the COMBO-17 survey. This survey offers an unprecedented data set for studying lens galaxies at $z=0.2-0.7$ including redshift information and spectral classification from 17 optical filters for objects brighter than $R=24$. So far, redshifts and classification for the lens galaxies have mainly been available for local surveys like the Sloan Digital Sky Survey (SDSS). Further, redshifts for the source galaxies have typically not been available at all but had to be estimated from redshift probability distribution which – for faint surveys – even had to be extrapolated.

To study the dark matter halos we parametrize the lens galaxies as singular isothermal spheres (SIS) or by Navarro-Frenk-White (NFW) profiles. In both cases we find a dependence of the velocity dispersion or virial radius, respectively, on lens luminosity and colour. For the SIS model, we are able to reproduce the Tully-Fisher/Faber-Jackson relation on a scale of $150h^{-1}~\mathrm{kpc}$. For the NFW profile we also calculate virial masses, mass-to-light ratios and rotation velocities.

Finally, we investigate differences between the three survey fields used here.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A white-light flare on 2001 March 10 was well observed in the H$\alpha$ line and Ca II$\lambda$8542 line using the imaging spectrograph installed in the Solar Tower Telescope of Nanjing University. Three small sunspots appeared in the infrared continuum image, one of which showed that the infrared continuum is enhanced by 4%-6% compared to the preflare value and it almost disappeared in the continuum image for about 3 min. Near the sunspot, there appeared a hard X-ray (HXR) source, the flux of which showed a good time correlation with the profile of the continuum emission. We propose that electron precipitation followed by radiative backwarming may play the chief role in heating the sunspot.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Determinations and measurements of the parallax of the Pleiades, obtained with ground-based studies and with Hipparcos data, are reviewed. A number of uncertainties in both sets of data are found. Although a further correction for abscissa correlations brings the Hipparcos determination closer to the ground-based value, the difference still seems too large. The new Hipparcos parallax determinations seem to reinforce a possible age related effect. A new reduction of the Hipparcos data is in progress. It reduces significantly the contribution of the attitude noise, providing higher accuracies and lower correlation levels for the brighter stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This article reviews the methods of measurement which allow us to infer the presence of magnetic fields in (A) stars. Beginning with the basic observational consequences of the Zeeman effect, we describe various modern spectroscopic and polarimetric techniques which allow us to directly detect and characterise magnetic fields in stellar photospheres. Sometimes, nature conspires to make such detections difficult, forcing us to rely on indirect (proxy) indicators of magnetism. This talk will also briefly discuss a number of these indirect field indicators, some of which demand space-based observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

There is now firm evidence that the ICM consists of a mixture of hot plasma, magnetic fields and relativistic particles. The most important pieces of evidence for non-thermal phenomena in galaxy clusters come from the diffuse Mpc-scale synchrotron radio emission (radio halos), observed in a growing number of massive clusters (Feretti 2003), and from hard X-ray (HXR) excess emission (detected in a few cases), which can be explained in terms of IC scattering of relativistic electrons off the cosmic microwave background photons (Fusco-Femiano et al. 2003). There is now growing evidence that giant radio halos may be naturally accounted for by synchrotron emission from relativistic electrons reaccelerated by some kind of turbulence generated in the cluster volume during merger events (Brunetti 2003). With the aim of investigating the connection between thermal and non-thermal properties of the ICM, we have developed a statistical magneto-turbulent model which describes the evolution of the thermal and non-thermal emission from clusters. We calculate the energy and spectrum of the magne-!tosonic waves generated during cluster mergers, the acceleration and evolution of relativistic electrons and thus the resulting synchrotron and inverse Compton spectra. Here we give a brief description of the main results, while a more detailed discussion will be presented in a forthcoming paper (Cassano & Brunetti, in preparation). Einstein-De Sitter cosmology, $H_0=50$ km s$^{-1}$ Mpc$^{-1}$, $q_0=0.5$, is assumed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the study of the gas mass fraction, $f_{\rm gas}$, properties of distant galaxy clusters observed within the XMM-$\Omega$project, based on a sample of distant ($z\sim 0.5$) clusters of median luminosity. These clusters were previously detected as serendipity ROSAT clusters surveys. We first study the $f_{\rm gas}$ profiles traced up to the virial radius in both Einstein de Sitter (EdS) and concordance cosmologies. We find that the mean gas fraction profile of our high-$z$ sample is similar to the local mean profile and in good agreement with numerical simulations predictions. This result confirms the self-similarity of the shape predicted by the simple scenario of structure formation up to high redshifts. We observe $f_{\rm gas}$ in the central part of distant clusters to lie below the local ones in the case of an EdS model, consistently with the observed evolution in the $\hbox{$L_{\rm X}$--$T$}$ relation, which is indeed found to be weaker than expected in a self-similar model. We investigate quantitatively this departure from scaling laws by comparing $f_{\rm gas}$ in our distant XMM clusters with those derived from the local sample at fixed scaled radii. We show that the internal structure is very complex, i.e. the variation of the gas mass fraction with radius, with temperature and with redshift reveals differences that cannot be described in a simple scaling scheme. The observed variations in the central parts are a clear indication that, in these regions, the argument based on the non-evolving $f_{\rm gas}$ with redshift cannot be used to infer the cosmological parameters, given the present (lack of) understanding of the gas physics in clusters. At the virial radius, where this argument could be valid, we find that the $\Lambda$CDM model is excluded at more than 3-$\sigma$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

When a new Near Earth Asteroid is discovered, it is important to know if there is the possibility of an impact with the Earth in the near future. In these last years second generation software for impact monitoring (CLOMON2 and SENTRY) have been developed and the performances have been significantly increased in comparison to the earlier, simpler and solitary system CLOMON. The two systems use the Line Of Variations (LOV) approach: they sample the LOV, an 1-dimensional subspace, to perform the sampling of the 6-dimensional confidence region. This approach is very useful when the confidence region is elongated and thin, that is an eigenvalue of the covariance matrix is much bigger than the others. When the observed arc is short (1$^\circ$ or less), usually for asteroids observed for few nights, the confidence region is like a flat disk and we propose to use a 2-dimensional sampling. We triangulate the admissible region in the $(r, \dot r)$ plane, using the nodes of triangulations as Virtual Asteroids (VAs). After orbit propagation we project the VAs and the triangulation on the Target Plane (TP) of a given epoch to study the existence of a Virtual Impactor (VI) and complex dynamical behaviors such as folds.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyzed 13 narrow-line Seyfert 1 galaxies (NLS1s) observed with XMM-Newton. Their X-ray continua are well parameterized by a combination of a hard power law and thermal emission from a standard Shakura-Sunyaev accretion disk. However, the observed disk temperatures are significantly higher than the prediction from the standard disk, and the temperatures are distributed within an extremely narrow range (0.15–0.22 keV) in spite of the wide range of luminosities (LX = 1041–45 erg s−1). Furthermore, we found an anti-correlation between the disk temperature and luminosity of PKS 0558–504. These results strongly indicate the breakdown of the standard accretion picture in NLS1s. We suggest that a slim disk, which is a stable disk solution under a high mass-accretion rate, could be able to explain the observational results, if the photon trapping effect is properly taken into account.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Some theoretical problems associated with the presence of large-scale magnetic fields in A stars are reviewed. Possible implications of some recent theoretical and observational results are discussed, with particular attention to the survival of fields from the ISM and their long-term stability. A more coherent picture of the origin of the strong large-scale fields seen in the magnetic CP stars may be beginning to emerge.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The latitudinal time distribution of sunspots (butterfly diagram) was studied by Becker (1959) and Antalová & Gnevyshev (1985). Our goal is to revisit these studies. In the first case we check whether there is a poleward migration in sunspot activity. In the second case we confirm the results, and make more quantitative statements concerning their significance and the position of the activity peaks.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Hubble Deep Field (North) and the flanking fields are used investigate the occurrence of multiple weak lensing deflections along the line of sight in relatively deep imaging data ($z_{\rm lens} \sim 0.6$, $z_{\rm source} \sim 1.2$). Ray tracing simulations of galaxy–galaxy lensing in the HDF-North show that proper inclusion of multiple weak deflections is important for a correct prediction of the net shear for most sources, and for a given source redshift the number of multiple weak deflections is largely insensitive to the cosmography. The effects of multiple weak deflections on the magnitude of the weak lensing signal are, of course, strong functions of the adopted halo parameters. Independent of the halo parameters, however, the closest lens to a source (in projection on the sky) is not the strongest lens in the case of more than 50% of the sources which acquire a net shear of $\gamma \lo 0.01$. In addition, multiple weak deflections result in a tangential shear about the lens centers that is greater than the tangential shear that would occur if source galaxies were lensed solely by the closest lens. Further, multiple weak deflections give rise to correlated image ellipticities and account for a substantial amount of the total cosmic shear signal on small angular scales in $\Lambda$CDM and open CDM models.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The distance to the Pleiades open cluster is of fundamental importance to many aspects of stellar astrophysics but is currently controversial. The ‘long’ distance scale of $132 \pm 3$ pc is supported by main sequence fitting analyses, ground-based parallax observations and analysis of the astrometric binary Atlas. The ‘short’ distance scale of $120 \pm 3$ pc comes from parallaxes observed by the Hipparcos satellite. Munari et al. (2004) studied the detached eclipsing binary HD 23642 and found a distance of $132 \pm 2$ pc. We reanalyse the data of Munari et al. to explore the different methods of estimating the distance of an eclipsing binary system. We use the surface brightness relations of Kervella et al. (2004) to find a distance of $139 \pm 4$ pc, which is consistent with the ‘long’ Pleiades distance and in disagreement with the Hipparcos parallax distances to the Pleiades and to HD 23642 itself. By comparing the observed masses and radii of the binary with theoretical predictions we derive a metal abundance approximately equal to or slightly greater than solar. Further photometric observations of the binary are needed to improve the analysis.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study in focus to the multi-wavelength radio spectra associated with quite strong CME events observed in the time interval of October 26–28, 2003. Using multi-wavelength observations recorded by WIND/WAVES experiment, Learmouth Spectrograph (Australian), PHOENIX-2 (Switzerland), Hiraiso (Japan), DAM/Nançay (France), Izmiran (Russia) and Huairou/NAOC (China), an analyzing of radio bursts was performed for the those events over a large coronal region across the microwave, the decimetric wavelength, the metric wavelength and even to much longer wavelength. The composite spectra indicate there were many complicated structures of radio bursts, including type II bursts, type IV bursts, type III bursts, drifting pulsation structures (DPS) and many radio fine structures (FS).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The work presents the nonlinear interrelation estimation between paleoclimatic time series using reconstructions of topological models obtained by embedding corresponding time series into $R^{n}$To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High-resolution spectroscopic and spectropolarimetric data of the rapidly oscillating Ap star HD 24712 (HR 1217, DO Eri) has been analysed including modelling the vertical elemental abundance structures. We study the interaction and the relation of the vertical (stratification) and the horizontal (spots) abundance characteristics of Fe and the stellar magnetic field. By this synopsis and the relation of our results to the analysis of high resolution and high time resolved observations (Sachkov et al. 2005) we are likely to gain new insights about the atmospheric structure and the geometry, the origin, and the evolution of the magnetic fields of roAp stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The gravitational lensing constraints on the small mass end of the $\Lambda$CDM mass function are discussed. Here a conservative approach is taken where the most difficult to explain image flux anomalies in strong lenses are emphasized. Numerical simulations are performed to compare predictions for the $\Lambda$CDM small scale mass function with the observed flux ratios. It is found that the cusp caustic lens anomalies and the disagreements between monochromatic flux ratios and simple lens models can be explained without any substructure in the primary lenses' dark matter halos. Extragalactic $\Lambda$CDM halos are enough to naturally explain these cases. This does not mean that substructure within the host lens is not contributing. In fact, it could be dominating the lensing. It should also be noted that this extragalactic population has not been directly observed either.

Spectroscopic gravitational lensing provides more information on the nature of these substructures. In the one relevant case in which this technique has been used so far, observations of Q2237+0305, there is evidence that there are more small mass halos ($\sim 10^6\msun$) than is expected in the $\Lambda$CDM model.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We determined a central black hole mass of $M_{\rm virial}=1.8\pm 0.4\times 10^{7} M_{\odot}$ in the Seyfert galaxy Mrk 110 with reverberation mapping methods – i.e. from integrated optical line profile variations as well as from velocity-delay maps. But this black hole mass depends on the unknown orientation of the central accretion disk. Here we report on the detection of gravitational redshifted emission in the variable fraction of all broad optical emission lines in Mrk 110. We derive a central black hole mass of $M_{\rm grav}=14.0\pm 3.0\times 10^{7} M_{\odot}$ with this method. This value is independent on the orientation of the accretion disk. A comparison of both black hole mass estimates allows to determine the central accretion disk inclination angle i to 21° in Mrk 110, and therefore the orientation of the spin axis of the central black hole.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html