Long-term behaviour of the interplanetary magnetic field is compared with that of the quadrupole harmonic of the solar axisymmetric magnetic field. Substantial correlation between them is found both on the time scale of 22-yr cycle and on the shorter time scale of several years.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

ACS observations of massive lensing clusters permit an order of magnitude increase in the numbers of multiply-lensed background galaxies identified behind a given cluster. We have developed a code to take the pixels belonging to any given image and generate counter-images with full resolution, so that multiple systems are convincingly and exhaustively identified. Over 130 images of 35 multiply lensed galaxies are found behind A1689, including many radial arcs and also tiny counter-images projected on the center of mass. The derived mass profile is found to flatten steadily towards the center, like and NFW profile, with a mean slope $d{\log{\Sigma}}/d{\log{r}}\approx-0.55\pm0.1$, over the range $r<250$ kpc/h, which is somewhat steeper than predicted for such a massive halo. We also clearly see the expected geometric increase of bend angles with redshift, however, given the low redshift of A1689, $z=0.18$, the dependence on cosmological parameters is weak, but using higher redshift clusters from our GTO program we may derive a more competitive constraint.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The RHESSI hard X-ray spectra are investigated for a total of 23 CME-related flares. It is found that about 17%, 70%, and 13% of the samples can be attributed to type A, B, and C, respectively. These ratios are not significantly different from those obtained using the data of HXRBS/SMM, although the ratio of type C in our CME-related flares is a little higher. More samples are obviously necessary to study the difference of hard X-ray spectra between the CME-related flares and non-CME-related flares.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this contribution we present the detection of two WHIM filaments in the Chandra-LETG spectrum of Mkn 421. This spectrum has been obtained following 2 of our pre-approved Target of Opportunity requests to observe Blazars in outburst to efficiently ‘X-ray’ the IGM at high spectral resolution. These observations caught the source at the unprecedented levels of 60 and 40 mCrab in the soft X-ray (0.5-2 keV) band. We detect, for the first time, two WHIM filaments at redshifts of z=0.011 and z=0.027, respectively. Based on these two detections and on the upper limits on associated HI and OVI absorption as inferred from the HST and FUSE spectra of Mkn 421, we estimate a number of WHIM filaments per unit redshift, with He-like ion columns $N_{X} \gs 8 \times 10^{14}$ cm$^{-2}$ of $dN/dz = 67^{+88}_{-43}$, and a baryon mass density of $\Omega_b = 0.021^{+0.028}_{-0.014}$, virtually all of the ‘missing baryons’ at $z\lt1$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The black-drop effect bedeviled attempts to determine the Astronomical Unit from the time of the transit of Venus of 1761, until dynamical determinations of the AU obviated the need for transit measurements. By studying the 1999 transit of Mercury, using observations taken from space with NASA's Transition Region and Coronal Explorer (TRACE), we have fully explained Mercury's black-drop effect, with contributions from not only the telescope's point-spread function but also the solar limb darkening. Since Mercury has no atmosphere, we have thus verified the previous understanding, often overlooked, that the black-drop effect does not necessarily correspond to the detection of an atmosphere. We continued our studies with observations of the 2004 transit of Venus with the TRACE spacecraft in orbit and with ground-based imagery from Thessaloniki, Greece. We report on preliminary reduction of those data; see http://www.transitofvenus.info for updated results. Such studies are expected to contribute to the understanding of transits of exoplanets. Though the determination of the Astronomical Unit from studies of transit of Venus has been undertaken only rarely, it was for centuries expected to be the best method. The recent 8 June 2004 transit of Venus provided an exceptionally rare opportunity to study such a transit and to determine how modern studies can explain the limitations of the historical observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have modeled the time-variable profiles of the Hα emission line from the non-axisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a $10^{6} M_{\odot}$ black hole. We find that the line profiles at these very early stages of the evolution of the post-disruption debris do not resemble the double peaked profiles expected from a rotating disk since the debris has not yet settled into such a stable structure. The predicted line profiles vary on fairly short time scales (of order hours to days). As a result of the uneven distribution of the debris and the existence of a ‘tidal tail’ (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Given the illuminating UV/X-ray light curve, we also model the Hα light curve from the debris.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study the population of asteroids inside the 2/1 mean motion resonance with Jupiter, in the so called Hecuba gap. Origin of these bodies is not well understood: (i) the long-lived (stable) population may be primordial, but this contradicts its steep size distribution, while (ii) the short-lived (unstable) population requires an efficient sustaining mechanism. Our working hypothesis is that the unstable asteroids are continuously resupplied from outside the resonance by the Yarkovsky effect. As a first step toward comparison of such model with observations, we report here an update of the observed population of asteroids residing in the 2/1 Jovian resonance, mainly because the number of cataloged orbits increased substantially during the last few years. We found there are 153 numbered and multi-opposition resonant asteroids in total and we classified them into the three sub-populations according to their dynamical lifetime. Our work also allowed us to derive several important parameters such as asteroid locations inside the resonance or size distribution of the sub-populations. As a particular novelty, we identified 6 asteroids located inside the high-eccentricity quasi-regular stable island, which previously seemed empty.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

When a layer of heavy matter is above lighter matter in a star, the inverse $\mu $-gradient may lead to thermohaline (or double-diffusive) convection. This has been studied in the past for helium-rich atmospheres, but it may also occur for metal-rich layers. It has recently been studied for the accretion of hydrogen poor material onto the host stars of exoplanets. These stars present a metallicity excess compared to stars in which no planets have been detected. However, the reason for this excess is still a subject of debate. It may be primordial or the result of accretion, or both. In this last case, thermohaline convection may lead to “metallic fingers” which partially dilute the accreted matter inside the star. Such an effect can also be important in the chemically peculiar A stars in which metals accumulate in the atmospheric layers.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present an analysis of the reliability of computation of maximum Characteristic Exponents of Lyapunov from the numerical integrations of asteroid orbits over finite intervals of time. We used two complementary approaches - a comparison of the LCE estimates from the backward and forward integrations of orbits, and a comparison of the estimates coming from the integrations of the same initial conditions over different time spans. The main conclusion is that for a vast majority of asteroids ($> 80\%$) the results can be considered as reliable enough to reveal the very nature and basic properties of the motion.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Statistics analysis of decimetric type III bursts, coronal mass ejections (CMEs) and H$\alpha$ flares are carried out. The relevant radio events observed from the 625-1500MHz spectrograph at the Yunnan Observatory during the 23rd solar cycle. It is found that the relation between the decimetric type III bursts and CMEs is not closer than that between the type II radio bursts and CMEs; All H$\alpha$ flares generated decimetric type III bursts and correlated with CMEs are all gradual flares. The higher the energy of the flare correspond to the faster the initial velocity of the CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Geometry of the polar magnetic field is changing during the activity cycle. Tangents to polar ray structures are usually crossed near some point below the surface. This point can be named as a “magnetic focus”. The distance $q$ between the focus and the center of the solar disk changes from the maximum value about 0.7 $R_\odot$ at solar minimum activity to the minimum value about 0.5 $R_\odot$ at solar maximum. This behavior has not been understood till now. Really, all tangents to field lines near the pole of the axially symmetric potential magnetic field described by zonal spherical harmonics cross at the same point. However, the greater is the number of a harmonic, the closer to the surface is the crossing point. As far as at activity maximum high harmonics dominate, the behavior of the focuses seems to be in contradiction with the results of the harmonic analysis. We have found that the focus depth changes could be explained by complicated relationship between the harmonics of “new” and “old” cycle near the instant of the polar magnetic field reversal.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We are currently developing an analytical theory of an artificial satellite of the Moon. It is an interesting problem because the dynamics of a lunar orbiter is quite different from that of an artificial satellite of the Earth, by at least two aspects: the $J_2$ lunar gravity term is only $1/10$ of the $C_{22}$ term and the third body effect of the Earth on the lunar satellite is much larger than the effect of the Moon on a terrestrial satellite. So we have to account at least for these larger perturbations. We use here the method of the Lie Transform as perturbation method. The Hamiltonian of the problem is first averaged over the fast angle, in canonical variables. The solution is developed in powers of the small factors linked to $ n_{\Moon}$, $J_2$, $C_{22}$ and to the Earth's position. The Earth location is determined by the lunar theory ELP2000 (Chapront-Touzé & Chapront 1991) from which we take the leading terms. Series developments are made with our home-made Algebraic Manipulator, the MM (standing for “Moon's series Manipulator”). The results are obtained in a closed form, without any series developments in eccentricity or inclination. So the solution applies for a wide range of values, except for few isolated critical values. We Achieved, among others, second order results for the combined effect of $J_2$ and $C_{22}$. As a side result, we were able to check the second order generator $\mathcal{W}_{2}$ given by Kozai for the effect of the $J_2$ term on an artificial satellite.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe recent discoveries of low column density (N$_{\rm HI} = 10^{12.5-16.0}$ cm$^{-2}$) H I Ly$\alpha$ absorbers made with the Hubble Space Telescope (HST) which have allowed us a first look at gas in local intergalactic space; i.e., between us and the “Great Wall”. These absorbing clouds account for 29 $\pm$ 4% of all baryons at $z$=0 and are, in general, only loosely related to individual galaxies. Owing to the proximity of these absorbers to the Earth, the 187 absorbers in our combined GHRS + STIS sample provide our best view of the relationship between Ly$\alpha$ absorbers and galaxies, voids, and supercluster filaments. While only a few of the very strongest absorbers in our sample appear associated with individual galaxies, the majority (78%) are associated with large-scale filamentary structures of galaxies, while 22% are found in galaxy “voids”. Amongst the highest column density absorbers (with N$_{\rm HI}\approx$ 10$^{16}$ cm$^{-2}$) in our sample, we find a low-ionization, metal-bearing absorber associated with a post-starburst dwarf galaxy $\sim$ 70h$^{-1}_{70}$ kpc away. The detailed properties of the absorber and the galaxy provide strong evidence that these two are causally related. We argue that many/most weak metal absorption systems could be due to outflowing “superwinds” from dwarf galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

KUBÁT: What are the differences between both codes for convection simulations without magnetic fields which we have just seen?

FREYTAG: Both codes solve the same set of basic equations and rely on very similar fundamental assumptions. However, the algorithms used to solve the hydrodynamics or the radiation transport equations differ. The codes have no routines in common. There is an ongoing project to perform a simulation of solar granulation with both codes, relying on the very same settings (grid, model extension, equation of state, opacities, ray system, etc.). The remaining differences are tiny, for example, much smaller than the difference between the 2D and the 3D models. Both codes have some extensions (for instance dust or magnetic field) not (yet) found in the other.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Several radio-loud objects exhibit a complex structure when observed at radio wavelengths: a stationary core, which is thought to harbour the central engine that powers the AGN phenomena, and a relativistic jet, formed by several superluminal components. In some cases, jet components are ejected with different apparent proper motions and directions on the plane of the sky. Moreover, these sources can also show signatures of long-term periodic variability in their historical optical light curve. In this work, we selected the objects 3C 120 and 3C 345, which exhibit both characteristics mentioned above, and interpret them in the framework of jet inlet precession. A brief discussion about what kind of mechanism could be responsible for jet precession is also presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from weak lensing analyses of 20 high-redshift clusters in the ESO Distant Cluster Survey (EDisCS) from both deep optical VLT and HST/ACS imaging. We find that the EDisCS sample is composed primarily of clusters that are less massive than those in current X-ray selected samples at similar redshifts, but that all of the fields are likely to contain massive clusters rather than superpositions low mass groups. We find good agreement between the weak lensing measurements in the VLT and ACS images. Finally we determine the noise level in the shear measurements for the VLT fields as a function of exposure time and seeing and demonstrate that future ground-based surveys which plan to perform deep optical imaging for use in weak lensing measurements must achieve point-spread functions smaller than a median of $0\farcs 6$ FWHM.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the review of temporal variations of the solar neutrino flux, including our original results of investigations of the solar neutrino flux variations in 1970–1997.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present long-slit HST/STIS measurements of the ionized-gas kinematics in the nucleus of three disk galaxies, namely NGC 2179, NGC 4343, NGC 4435. The sample galaxies have been selected on the basis of their ground-based spectroscopy, for displaying a strong central velocity gradient for the ionized gas, which is consistent with the presence of a circum nuclear keplerian disk (CNKD, Bertola et al. 1998; Funes et al. 2002) rotating around a super massive black hole (SMBH). For each target galaxy we obtained the Hα and [NII] 6583 Å kinematics along the major axis and two 0."25 parallel offset positions. Out of three objects only NGC 4435 turned out to have a disk of ionized gas in regular motion and a regular dust-lane morphology. Preliminary modeling indicates a SMBH mass (M[bull ]) one order of magnitude lower than the one expected from the M[bull ]−σc relation for galaxies (Ferrarese & Merritt 2000; Gebhardt et al. 2000).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Atomic diffusion may play a significant role for the Sun and Population I Main Sequence stars up to some 25000 K, Population II turnoff stars and cluster age determinations, horizontal branch stars (including sdOs and sdBs), white dwarfs and neutron stars. In all these cases, radiative accelerations play a significant role. A stars are, however, arguably those that show most prominently the effects of atomic diffusion. In so far as the effects of accretion, mass loss, turbulence and meridional circulation may be neglected in the evolutionary models of A stars, the effects of atomic diffusion in them have now been calculated from first principles and are presented using complete evolutionary models of 1.7 and 2.5 $M_{\odot}$ stars. Their abundance anomalies are not only superficial, but extend over a significant fraction of the stellar radius. Iron convection zones appear at a temperature of about 200000 K. Abundance anomalies similar to those observed in Am stars are produced. However the comparison with the observations requires linking atmospheres to interior evolution. Models that have been proposed to take into account atomic diffusion in atmospheric regions to explain observations are critically reviewed. They depend on a number of parameters. Unfortunately the atmospheric regions are imperfectly modeled, the magnetic field is not taken into account, and important hydrodynamic processes currently require arbitrary parameters for their description.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Estimates of the region of Nekhoroshev stability of Jupiter's Trojan asteroids are obtained by a direct (i.e. without use of the normal form) construction of formal integrals near the Lagrangian elliptic equilibrium points. Formal integrals are constructed in the Hamiltonian model of the planar circular restricted three body problem (PCRTBP), and in a mapping model (Sándor et al. 2002) of the same problem for small orbital eccentricities of the asteroids. The analytical estimates are based on the calculation of the size of the remainder of the formal series by a computer program. An analysis is made of the accumulation of small divisors in the series. The most important divisors introduce competing Fourier terms with sizes growing at similar rates as the order of truncation increases. This makes impossible to improve the estimates by considering nearly resonant forms of the formal integrals for particular near-resonances. Improved estimates were obtained in a mapping model of the PCRTBP. The main source of improvement is the use of better variables (Delaunay). Our best estimate represents a maximum libration amplitude $D_p=10.6^0$. This is a quite realistic value which demonstrates the usefulness of Nekhoroshev theory.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html