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

In the last few years, new instruments mounted at modern large telescopes, as well as satellite instruments, have given to us the possibility of obtaining observations of much higher quality than in the past. Yet, the large majority of observations of A-type stars are performed with small to middle size class telescopes. In this paper I discuss the scientific case for the use of large size class telescopes for the A-star research.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Compact groups of galaxies recently have been discovered in association with several strong gravitational lens systems. These groups provide additional convergence to the lensing potential and thus affect the value of $H_0$ derived from the systems. Lens system time delays are now being measured with uncertainties of only a few percent or better. Additionally, vast improvements are being made in incorporating observational constraints such as Einstein ring structures and stellar velocity dispersions into the lens models. These advances are reducing the uncertainties on $H_0$ to levels at which the the effects of associated galaxy groups may contribute significantly to the overall error budget. We describe a dedicated multiwavelength program, using Keck, HST, and Chandra, to find such groups and measure their properties. We present, as a case study, results obtained from observations of the CLASS lens system B1608+656 and discuss the implications for the value of $H_0$ derived from this system.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Model atmospheres of A and B stars are computed taking into account magnetic line blanketing. These calculations are based on the new stellar model atmosphere code LLMODELS which implements a direct treatment of the line opacities and ensures an accurate and detailed description of the line absorption. The anomalous Zeeman effect was calculated for field strengths between 1 and 40kG and a field vector perpendicular to the line of sight. The magnetically enhanced line blanketing changes the atmospheric structure and leads to a redistribution of energy in the stellar spectrum. The most noticeable feature in the optical region is the appearance of the $\lambda$5200 broad, continuum feature. However, this effect is prominent only in cool A stars and disappears for higher effective temperatures. The presence of a magnetic field produces an opposite variation of the flux distribution in the optical and the UV regions. A deficiency of the UV flux is found for the whole range of considered effective temperatures, whereas the “null wavelength region” where the flux remains unchanged shifts towards the bluer wavelengths for higher temperatures.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

HD 34282 has been found to pulsate during a systematic search for short-term photometric variability in Herbig Ae/Be stars with the goal of determining the position and size of the pre-Main Sequence instability strip. Simultaneous Strömgren photometry is used in the frequency analysis, yielding two frequencies with values of $\nu_1 = 79.5$ and $\nu_2 = 71.3$ cycle ${\rm d}^{-1}$. The main period, with a value of 18.12 min, represents the shortest period observed up to now for a $\delta$ Scuti-type pulsator. A preliminary seismic modelling, including instability predictions and rotation effects, has been attempted. Both, Main Sequence and pre-Main Sequence models predict modes in the range of 56 to 82 cycle ${\rm d}^{-1}$ (between 648 and 949 $\mu{\rm Hz}$), corresponding to oscillations of radial order n from 6 to 8. The mode identification is not discriminating due to the large error bars attached to the data, therefore, all possible non-radial and radial modes up to $\ell = 3$ are compatible with the observed oscillations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this review, I will briefly discuss the hypotheses made in the treatment of modern rotating stellar models and review the expected efficiency of mixing along the HR diagram. The role of mixing in the localization of abundance anomalies will also be discussed. Finally, I will show how mass loss and gravitational settling of helium may influence the evolution of rotating stars, and how A stars can play a unique role in constraining our models.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Designating a star as of A-type is a result of spectral classification. After separating the peculiar stars from those deemed to be normal using the results of a century of stellar astrophysical wisdom, I define the physical properties of the “normal” stars. The hotter A stars have atmospheres almost in radiative equilibrium. In the A stars convective motions can be found which increase in strength as the temperature decreases.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe the current status of a programme we started a few years ago to observe a large number of A/F and Am/Fm stars in open clusters of various ages. Spectra were obtained with the AURELIE and ELODIE spectrographs at a resolving power of about 40000 and $S/N$ ratios from 100 up to 500. Abundances of 11 chemical elements have been derived by using Takeda's (1995) procedure. A short review on previous abundance determinations of A and F dwarfs in open clusters and a progress report on the current status of this project are presented. New abundance determinations for 24 A and F dwarfs in the Coma Berenices cluster are presented. These abundance determinations serve to set constraints to self-consistent evolutionary models of A and F stars including transport processes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use $\Lambda$CDM numerical simulations to model the density profiles and substructure populations in a set of sixteen dark matter halos with resolutions of up to seven million particles within the virial radius. These simulations allow us to follow robustly the formation and evolution of the central cusp over a large mass range of 10$^{11}$ to 10$^{14}$ $\msun$ down to approximately 0.5% of the virial radius, and from redshift 5 to the present. The cusp of the density profile is set at redshifts of two or greater and remains remarkably stable to the present time, when considered in non-comoving coordinates.

We fit our halos to a 2 parameter profile where the steepness of the asymptotic cusp is given by $\gamma$, and its radial extent is described by the concentration, $c_{\gamma}$. In our simulations, we find $\gamma$ = 1.4 - 0.08Log($M/M_*$) for halos of 0.01$M_*$ to 1000$M_*$, with a large scatter of $\Delta\gamma \sim \pm 0.3$; and $c_{\gamma} = 8(M/M_*)^{-0.15}$ with a large $M/M_*$ dependent scatter roughly equal to $\pm c_{\gamma}$. Our redshift zero halos have inner slope parameters ranging approximately from r$^{-1}$ to r$^{-1.5}$, with a median of roughly r$^{-1.3}$. This two parameter profile fit works well for all halo types present in our simulations, whether or not they show evidence of a steep asymptotic cusp.

The substructure population is independent of host halo mass and redshift with halo to halo scatter in the substructure velocity distribution function of a factor of roughly two to four. The radial distribution of substructure halos (subhalos) is consistent with the mass profile over the radial range where the possibility of artificial numerical disruption of subhalos can be most reliably excluded, r$\simgt$0.3 r$_{vir}$, although a weakly shallower subhalo profile is favored by the data. We discuss the implications that our results have on gravitational lensing studies of halo structure.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

The nature and the location of the lenses discovered in the microlensing surveys done so far towards the LMC remain unclear.

This contribution is comprised of two distinct parts. In the first part, motivated by these questions, we compute the optical depth for the different intervening populations and the number of expected events for self-lensing, using a recently drawn coherent picture of the geometrical structure and dynamics of the LMC disk. By comparing the theoretical quantities with the values of the observed events it is possible to put some constraints on the location and the nature of the machos. Clearly, given the large uncertainties and the few events at our disposal it is not yet possible to draw sharp conclusions, nevertheless we find that up to 3-4 macho events might be due to lenses in LMC, which are most probably low mass stars, but that hardly all events can be due to self-lensing. A plausible solution is that the events observed so far are due to lenses belonging to different intervening populations: low mass stars in the LMC, in the thick disk, in the spheroid and some true machos in the halo of the Milky Way and the LMC itself. We report also on recent results of microlensing searches in direction of the M31 galaxy, by using the pixel method. The present analysis still does not allow yet to draw sharp conclusions on the macho content of the M31 galaxy.

In the second part (section 5), a preliminary account of the final results from the EROS-2 programme is presented. Based on the analysis of 33 million LMC and SMC stars followed during 6.7 years, strict limits on the macho content of the galactic halo are presented; they cover the range of macho masses between 0.0001 and 100 solar mass. The limits are better than 20% (resp. 5%) of the standard halo for masses between 0.0002 and 10 (resp. 0.001 to 0.1) solar mass. This is presently the data set with the largest sensitivity to halo machos.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html