A review of recent work on pulsating A stars is presented. The types of pulsating stars are the roAp, $\delta$ Scuti, $\lambda$ Bootis, Am stars, pre-Main Sequence pulsating A stars and $\alpha$ Cygni stars (pulsating A supergiants). Population II pulsating A stars such as SX Phe (blue stragglers) and RR Lyraes are also discussed. The emphasis is on the physics that can be derived from the study of stellar pulsations and suggestions for further progress.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The study of orbital parameters of multiple Ap stars may lead to new suggestions about the origin and magnetic properties of the components. 53 Cam is one of the best studied binaries among Ap stars. However, the nature of its secondary star remains unclear despite the wealth of spectroscopic observations. The system was first directly resolved by speckle interferometry method in 1980 at the 4 m KPNO telescope McAlister et al. (1983). The authors supposed that the magnitude difference between the components could be close to zero. From that time, 16 speckle measurements of the system were made, including 7 observations collected with the SAO 6 m telescope. In addition to relative positions of the components, speckle observations from the 6 m telescope provide high accuracy magnitude difference estimates.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

Chemically peculiar stars are ideal astrophysical laboratories for furnishing a wide range of theoretical and observational aspects of our knowledge of the physical processes in stars. Recent dramatic improvements in the quality of the observational data and refinements of the modelling techniques led to an emergence of a new branch of stellar astrophysics which is focused on the reconstruction and the understanding of the origin of the three-dimensional structures in stellar surface layers. In this contribution I present an overview of recent results of the detailed modelling of the chemical nonuniformities, the magnetic and the pulsation velocity fields in the atmospheres of A stars. New Doppler imaging analyses of the magnetic field and the chemical inhomogeneities reveal an unexpected complexity of the surface formations and suggest that nonmagnetic phenomena play an important role in shaping the geometry of chemical spots. Consideration of the line profile shapes observed at high spectral and time resolution has made it possible to probe the radial dependence of the chemical abundances and the pulsation characteristics of cool pulsating Ap stars. An extension of Doppler mapping to the reconstruction of non-radial stellar oscillation structure delivers a solution of the long-standing problem of the pulsational geometry of roAp stars and helps to elucidate the interrelation between the pulsations, the magnetic field and the stellar rotation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Diffraction limited 30m class telescopes will play an important role in gravitational lensing studies, coming online in approximately 2015. As imaging telescopes they will complement the $\sim$6m JWST, probing to smaller angular scales in greatly magnified objects near critical lines and for measuring shear of objects below the JWST angular scale, such as luminous super-star clusters at high redshift. The high source density will allow more detailed mass mapping in the weak lensing regime and will be useful in breaking the cosmology-lens potential degeneracy in strong lensing. As multi-object spectrographs 30m telescopes should provide spectra over the entire optical and near infrared spectrum region. The statistical distribution of redshifts needed to invert projected shear measurements and calibration of photometric redshifts for “tomography” will be available to flux levels around 5-10 nano-Jansky (approx 29.5 m$_{AB}$). However, a one nJy object is expected to require $\sim$500 hours to acquire a redshift, which is most of the dark time in an observing season. Accordingly “gravitational telescopes” will be an important tool for probing the very faint high redshift universe, magnifying a few square arc-seconds at a time by factors of 10-1000.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The measurement of weak gravitational lensing is currently limited to a precision of $\sim$10% by instabilities in galaxy shape measurement techniques and uncertainties in their calibration. The potential of large, on-going and future cosmic shear surveys will only be realised with the development of more accurate image analysis methods. We present a description of several possible shear measurement methods using the linear “shapelets” decomposition. Shapelets provides a complete reconstruction of any galaxy image, including higher-order shape moments that can be used to generalise the KSB method to arbitrary order. Many independent shear estimators can then be formed for each object, using linear combinations of shapelet coefficients. These estimators can be treated separately, to improve their overall calibration; or combined in more sophisticated ways, to eliminate various instabilities and a calibration bias. We apply several methods to simulated astronomical images containing a known input shear, and demonstrate the dramatic improvement in shear recovery using shapelets. A complete IDL software package to perform image analysis and manipulation in shapelet space can be downloaded from www.astro.caltech.edu/~rjm/shapelets/.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Diffusion of elements in a stellar plasma is strongly modified by the presence of magnetic fields for two primary reasons. The first is that the average motions of ions in outer atmospheres are, because of their charge, substantially constrained by the magnetic field. Both its intensity and orientation play a role. The second is the Zeeman desaturation of absorption lines that often produces amplifications of the radiative accelerations. These effects are important and must lead to the building of complex surface abundance structures. I will present how these two effects are generally modeled and what results have, up to now, been obtained. Future developments will also be considered.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The global bipolar structure of the magnetic surface field is asymmetric for many stars, making its analytical description by an expansion of spherical harmonics problematic because of the coordinates. Landstreet (1970) proposed that the asymmetry could be understood assuming a decentered magnetic dipole in the stellar interior. Its surface field can be calculated for different arrangements inside and outside the star using the Magnetic Charge Distribution method. We demonstrate the effect for the two cases of the shift of the dipole along and perpendicular to the radial direction.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Radiation hydrodynamics simulations have been used to produce numerical models of the convective surface layers of a number of stars, including the Sun and other stars on or above the main-sequence, white dwarfs of type DA, and red supergiants.

While granulation of main-sequence solar-type stars resembles that of the Sun, the convective velocity fields of F-type stars are much more violent and accompanied by strong pulsations. The properties of the thin convection zone(s) of A-type stars differ again (see Fig. 1). In this contribution, the pattern and dynamics of their surface granulation, the photospheric velocity fields and their effect on line profiles are investigated, based on new 3-D models of surface convection in main-sequence A-type stars with $T_{\rm eff}$=8500 K and 8000 K. Furthermore, we will look below the surface to study overshoot and the interaction of the surface convection zone and the deeper helium II convection zone.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The existence of lensed quasars with splitting angles larger than $7''$ has been predicted on the basis of the cold dark matter model. We searched for these large-separation lensed quasars from the spectroscopically classified $\sim40,000$ quasars obtained by the Sloan Digital Sky Survey (SDSS), and succeeded in discovering the first lensed quasar by a cluster of galaxies, SDSS J1004+4112: It consists of four images, and the maximum separation is $14.62''$. Here we describe the discovery and the follow-up observations of this system, as well as the latest results of the large-separation lens search in the SDSS. We also present the new statistical model which fully incorporates non-sphericity of dark halos, and compare the theoretical predictions with the SDSS results.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present predictions for cosmological parameter constraints from combined measurements of second- and third-order aperture mass statistics of cosmic shear. The generalized third-order aperture mass is introduced and its relation to the convergence bispectrum is given. This quantity contains (in principle) all information about the bispectrum. Using ray-tracing simulations, we perform a Fisher matrix analysis for various cosmological parameters and show that the combination of $\langle M_{\rm ap}^2\rangle$ and $\langle M_{\rm ap}^3\rangle$ improves the parameter estimation significantly.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The current status of our knowledge of magnetic fields in A-type stars is reviewed with special emphasis on the progress achieved for “classical” Ap stars over the last four years. For those stars, the distribution of the strength of the field, its three-dimensional structure, and its relation with rotation and evolution are discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the first results of the CP star observations in the spectral regions of the Li I lines at $\lambda 6708$ and $\lambda 6104$ obtained with the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We calculate the synthetic spectra of TT Hya, an Algol-type eclipsing binary system which contains an A-type primary surrounded by a disc, and an evolved secondary which fills its Roche lobe. A new code SHELLSPEC was developed to solve the simple radiative transfer along the line of sight propagating through the 3D moving medium in LTE. The synthetic spectra are then compared with the observed ones which enable us to derive independent constraints on the behavior of the state quantities, the velocity field and the geometry of the disc.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Important results of magnetic CP star research in the last decade from photometric and spectroscopic observations are discussed. Hipparcos parallaxes confirm CP stars are Main Sequence stars. Photometric monitoring of the rapidly rotating stars provides evidences for the rotational braking on the Main Sequence. High signal-to-noise spectra with high resolution and time-resolution give strong support for chemical separation processes operating in stellar atmospheres (abundance stratification). There are also observational evidences for the departure of the temperature structure of cool CP star atmospheres from that for normal stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of a search for gravitational lensing of the cosmic microwave background (CMB) in cross-correlation with the projected density of luminous red galaxies (LRGs). The CMB lensing reconstruction is performed using the first year of Wilkinson Microwave Anisotropy Probe (WMAP) data, and the galaxy maps are obtained using the Sloan Digital Sky Survey (SDSS) imaging data. We find no detection of lensing; our constraint on the galaxy bias derived from the galaxy-convergence cross-spectrum is $b_g=1.81\pm 1.92$ ($1\sigma$, statistical), as compared to the expected result of $b_g\sim 1.7$ for this sample. We discuss possible instrument-related systematic errors and show that the Galactic foregrounds are not important. We do not find any evidence for point source or thermal Sunyaev-Zel'dovich effect contamination.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a new model of the lensing cluster of galaxies MS2137-23. By incorporating strong and weak lensing data in a fully elliptical lens modeling, we show that the total density profile must be close to the predictions of numerical simulations with an inner slope well consistent with a NFW profile. The model that best fits the lensing constraints is used to infer to line-of-sight velocity distribution (LOSVD) of stars in the central cD galaxy. This distribution is found to be far from Maxwellian. The important non-Gaussian tails produce a significant low-bias when measuring the velocity dispersion by assuming Gaussian absorption lines. In the case of MS2137, most of the information comes from multiples arcs. Internal kinematics of stars only help modeling the innermost kiloparsecs. However, in clusters with fewer constraints (no radial arcs for instance), a detailed modeling of both strong lensing and internal kinematics is crucial.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Recent spectroscopic observations of roAp stars with high spectral resolution and high time resolution show line profile variations (LPV) which seem to be similar to those seen in rapidly rotating B-type line-profile variables. At first glance these line profile variations seem to be in disagreement with the mode identification based on the photometric observations. We propose an interpretation according to which the observed line profile variations are a manifestation of a shock wave in the high atmosphere near the magnetic polar regions, and show that the line profile variations can be still understood in the framework of the oscillation mode being consistent with the photometric observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the theory of weak gravitational lensing in cosmologies with generalized gravity, described in the Lagrangian by a generic function depending on the Ricci scalar and a non-minimally coupled scalar field.

We work out the generalized Poisson equations relating the dynamics of the fluctuating components to the two gauge invariant scalar gravitational potentials, fixing the new contributions from the modified background expansion and fluctuations.

We show how the lensing observables are affected by the cosmic expansion as well as by the presence of the anisotropic stress, which is non-null at the linear level both in scalar-tensor gravity and in theories where the gravitational Lagrangian term features a non-minimal dependence on the Ricci scalar. We derive the generalized expressions for the convergence power spectrum, and illustrate phenomenologically the new effects in Extended Quintessence scenarios, where the scalar field coupled to gravity plays the role of the dark energy.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

New pulsating pre-main sequence (PMS) stars have been discovered in the young open clusters IC 4996 and NGC 6383 using CCD time series photometry in Johnson B and V filters. As the cluster ages are both smaller than 10 million years, all members later than spectral type A0 are still contracting towards the ZAMS, hence providing ideal candidates for searches of pulsation. A dozen stars in NGC 6383 and 35 stars in IC 4996 lie within the boundaries of the classical instability region in the Hertzsprung-Russell (HR) diagram, but pulsation was detected for only two of them in each cluster.

For the well-studied cluster NGC 2264, the two already known PMS pulsating members, V 588 Mon and V 589 Mon, have been analysed using new data from a multi-site campaign. All data collected since their discovery in 1972 build the basis for the first measurements of period changes in PMS pulsators.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html