The possibility of a quite high Li abundance in the Ap stars was first raised by Wallerstein & Merchant (1965). Since then many studies investigated the problem of Li. The more recent observations in the lithium region indicate that in some Ap stars the $\lambda 6708$ feature is variable and this variability can be explained by the existence of Li rich spots on the stellar surface. Atomic data for the Ce II$\lambda 6708.099$ were released by the D.R.E.A.M. database in 2002. The line was used to identify the prominent suspected Li-feature in post AGB stars and might as well be responsible for the absorption feature in Ap stars. Recent studies have mentioned this possibility, but it has yet to be investigated in more detail. Other physical phenomena, such as the occurrence of a partial Paschen-Back effect in the presence of magnetic fields, as well as possible hyperfine structure splitting of some Rare Earth transitions, must be taken into account to provide correct line identifications in the wavelength region around the Li-doublet at $\lambda 6708$. We discuss a possible strategy to clarify the presence of Li in Ap stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the results of the search for rapid periodic magnetic variations in $\gamma$ Equ. Observations were collected in August 1989 with the 6-m telescope of Special Astrophysical Observatory (Russia). We analysed a 3-hour series of 1720 rapid $B_{\rm e}$ measurements of $\gamma$ Equ obtained with an average time resolution of 6.6 s. A power spectrum analysis shows a period of $P = 3.596\,{\rm min}$. That period differs from the well-known photometric period of rapid variability $P_{\rm phot} = 12.44\,{\rm min}$. We do not confirm variations of the $B_{\rm e}$ field of $\gamma$ Equ with the $P_{\rm phot}$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We review the scientific objectives and the present status cosmic shear studies. We discuss the future prospects and the role cosmic shear could play in a precision cosmology era.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the results of the spectral monitoring of the chemically peculiar (CP2) star HD 3980 in the Li I$\lambda 6708$ spectral region. High spectral resolution observations ($R=88000$) were carried out at Mount Stromlo Observatory with the 74-inch telescope and the echelle spectrograph. HD 3980 is a late type Ap SrCrEu star with strong double-wave photometric variations in the visible and in the near infrared. We estimated the effective temperature, surface gravity, mass, luminosity, and radius of this star. The monitoring of this star shows strong spectral variations, especially in the profile of Li I$\lambda 6707.8$. We studied the variations of the equivalent width and position of the Li I line as a function of the rotating phase and compared them with the magnetic field variations and light curves taken from the literature. The synchronism of the variations of the Li I line profile, light curve, and magnetic field strength can be explained in terms of the oblique magnetic rotator model. The strong variations of position and intensity of this line with the rotation phase enable us to consider this star as a new member of the intriguing group of “Li-spotted” CP stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High $S/N$, high resolution CCD spectra of 10 Am binaries with different orbital elements, rotation and atmospheric parameters obtained with the 2-m telescope of NAO Rozhen (Bulgaria) were analyzed. We carried out preliminary abundance analyses of these stars and studied the possible dependences of abundance anomalies and [Ca/Fe] on their values of effective temperature, $v\sin i$, orbital period, and eccentricity. There are weak trends of [Ca/Fe] increasing with $v\sin i$ and decreasing with eccentricity and orbital period. [Ca] seems to be increasing with effective temperature, and [Fe] decreasing with $v\sin i$ and increasing with eccentricity. However we need to study more stars to confirm and disentangle the possible trends.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The current status of NLTE model atmosphere calculations of A type stars is reviewed. During the last decade research has concentrated on solving the restricted NLTE line formation problem for trace elements assuming LTE model atmospheres. There is a general lack of calculated NLTE line blanketed model atmospheres for A type stars, despite the availability of powerful methods and computer codes that are able to solve this task. Some directions for future model atmosphere research are suggested.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

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

A new parametric method that approximates the radiative accelerations of bound-bound and bound-free transitions at large optical depths is presented. The parameters found in these new equations are calculated for the following trace elements: C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, and Fe and are made available to potential users. This method can be easily implemented in existing codes to study atomic diffusion without needing large computing resources or access to large atomic and opacity data bases.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present $VR$ magnification ratios of the double quasar Q0957+561AB, which are inferred from frames taken with the 2.56m Nordic Optical Telescope. From two different photometric techniques ($pho2comC$ and $psfphot$) and a reasonable range for the time delay in the system (415–430 days), we find optical continuum ratios depending on the wavelength. These chromatic ratios are consistent with either differential extinction in a dust system or gravitational microlensing in the deflector. Although the dusty scenario is only viable for a compact dust cloud in the line of sight to the A component, the possible values for the differential extinction and the ratio of total to selective extinction in the $V$ band are surprisingly reasonable. To decide on the true origin of the anomalous ratios (extinction, microlensing or a mixed scenario), we are carrying out new monitoring campaigns and planning detailed observations from the best ground–based and space telescopes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using data from the new EBASIM spectrograph at the 2.1-m telescope of the Complejo Astronómico El Leoncito (CASLEO), two rather sharp-lined B stars 5 Aqr (=HD 198667, B9 III) and 30 Peg (=HD 211924, B5 IV) are being studied. The measurements are compared with those from the coudé spectrograph of the 1.22-m telescope of the Dominion Astrophysical Observatory (DAO). The equivalent width scales of the EBASIM and the DAO data are similar. As we found that the line profiles of 30 Peg are variable, we are trying to determine whether this star is a slowly pulsating B star. 5 Aqr has abundances close to those of the Sun.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

SigSpec is a new method to compute the significance of the amplitude levels in the frequency domain, based on the false-alarm probability associated with a peak in the amplitude spectrum. The underlying probability density function (PDF) of the amplitude spectrum generated by pure noise may explicitly be derived if treated as frequency and phase-dependent. A comparison of the analytical solution with the results of extensive numerical calculatgions provides excellent agreement. In addition, the SigSpec software has already demonstrated clear advantages compared with the commonly used Fourier methods in various respects. A few examples for ground-based as well as space photometry are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The shape and size of a galaxy-mass dark matter halo can only be measured using a luminous tracer, such as stars, gas or photons. In the last case, gravitational lensing of extended background sources provides many paths for photons to sample the gravitational potential of the lensing galaxy. Multiple independent light paths provide tighter constraints on the mass profile of the lens galaxy than is possible from single path sampled by the lensed images of unresolved sources.

Using software specifically developed to model resolved images, we analyse the optical and radio Einstein ring systems 0047-2808 and MG1549+3047. For 0047-2808, elliptical pseudo-isothermal models (e.g. SIE, PIEP) are able to reproduce the lensed image well, with a surface mass power-law $\Sigma \propto r^{-\gamma}$, best fitted by $\gamma = 1.07 \pm 0.03$, which is slightly steeper than isothermal. Using a stars-plus-halo model, we find the projected halo is rounder than the visible galaxy (axis ratio $0.82 \pm 0.01$) and aligned closely with the stars (offset $8^{\circ} \pm 1$). Preliminary results for MG1549+3047 also rule out the constant M/L model. A stars + PIEP model suggests a very round (axis ratio $\ge 0.98$) halo.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Convection and turbulence in stellar atmospheres have a significant effect on the emergent flux from A-type stars. The recent theoretical advancements in convection modelling have proven to be a challenge to the observers to obtain measurements with sufficient precision and accuracy to permit discrimination between the various predictions.

A discussion of the current observational techniques used to evaluate the various convection theories is presented. These include filter photometry, spectrophotometry, hydrogen lines, and metal lines. The results from these techniques are given, along with the successes and limitations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Convection is one of the most intricate processes studied in stellar astrophysics and has challenged both theorists and observers since the beginnings of astrophysics. But during the last two decades observational data of unprecedented resolution and accuracy have been collected in solar and stellar research which permit a new look at the field. An enormous increase of computer speed now permits solving more complete model equations with more accurate numerical approximations. Modelling and theoretical understanding of convection, however, are lagging behind observational progress and are still wanting.

As a background to the contributions to this session on convection, I first provide an overview on its basic physics and its observational evidence. I point out why astrophysicists have a general interest in improvements of our understanding of stellar convection and then focus on convection in A-stars with their unique combination of convection zones. I summarise how this richness of different manifestations can arise in A-stars, such as convection zones near the surface and in the core, several on top of each other, or some of them depleted by diffusion processes, suppressed by or even creating magnetic fields, suspected to create a chromosphere in some of them, or influenced by binaries, to name just a few. In the last part I will present a few recent results on modelling of convection in A-stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyse the sensitivity of cosmic shear 2-point statistics to the cosmological parameters, by using Monte Carlo Markov Chain (MCMC) methods. In particular, we investigate degeneracies among parameters and compare them to the CMB ones. Specializing on a Canada France Hawaii Telescope Legacy Survey (CFHTLS) type lensing survey and WMAP-1 year and CBI CMB data, we find cosmic shear information improves CMB cosmological parameters constraints by a factor of 1.5 – 2.5.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We review in this paper the main results recently obtained on the identification and study of very high-z galaxies using lensing clusters as natural gravitational telescopes. We present in detail our pilot survey with ISAAC/VLT, aimed at the detection of z$>7$ sources. Evolutionary synthesis models for extremely metal-poor and PopIII starbursts have been used to derive the observational properties expected for these high-$z$ galaxies, such as expected magnitudes and colors, line fluxes for the main emission lines, etc. These models have allowed to define fairly robust selection criteria to find z$\sim 7-10$ galaxies based on broad-band near-IR photometry in combination with the traditional Lyman drop-out technique. The first results issued from our photometric and spectroscopic survey are discussed, in particular the preliminary confirmation rate, and the global properties of our high-z candidates, including the latest results on the possible z=10.0 candidate A1835-1916. The search efficiency should be significantly improved by the future near-IR multi-object ground-based and space facilities. However, strong lensing clusters remain a factor of $\sim$ 5-10 more efficient than blank fields in the z $\sim$ 7-11 domain, within the FOV of a few arcminutes around the cluster core, for the typical depth required for this survey project.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A review of various types of evolved A stars is presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

BALEGA: Is there any sense in performing a speckle interferometric survey to search for secondaries among the Ap stars? As a rule, the secondary companion will be always fainter and cooler than the primary star. Therefore, its input into the common spectrum will be negligible. A good example is 53Cam with a magnitude difference between the components of 1.2.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a progress report on the POLLUX database which contains high resolution echelle spectra of standard stars and a library of synthetic spectra. This set of observed and synthetic spectra provides a broad coverage of the atmospheric parameters and spectral types across the HR diagram.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html