Two topics concerning A-type stars are discussed: starspots associated with the strong magnetic fields and the prospects for asteroseismology. Considering starspots as analogous to sunspots is misleading. The photosphere of starspots of a magnetic A-star is higher than the normal photosphere, contrary to sunspots. As for the prospects of asteroseismology, it is demonstrated how well (or poorly) we can probe the internal structure of the distant stars using a limited number of p-mode frequencies. Although the detectable eigenmodes must be limited to be $\ell \leq 4$, if the observational error is of the order of $10^{-3}$, inversion has still some hope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Lenses acting on the Cosmic Microwave Background can potentially be a very efficient and robust probe of the large-scale matter distribution in the Universe. Their most immediate signature is the way they affect the statistical properties of both the temperature and the polarization fields, in particular they both induce non-Gaussian properties that can be explicitly computed.

Investigations of those effects led to the elaboration of specific reconstruction procedures that aim at mapping the projected mass responsible of the lens effects. These techniques are now on solid ground and are remarkably efficient. However it is likely that our best chance to detect a lensing signal in CMB data in the coming years will be through the cross-correlation patterns they induce between CMB data and tracers of the large-scale structure. Clearly the detection of such an effect would be very fruitful in scrutinizing the gravitational instability picture.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In the pre-WMAP, pre-Supernova-Ia-Hubble-diagram era, quasar lensing statistics stubbornly indicated low values of $\Omega_{\Lambda}$. In contrast, a number of recent lensing statistics studies either find the data support the standard $\Lambda$CDM picture, or simply take the standard cosmological parameters as a given. Have the data or the analyses changed or improved, and how? I review several of the “historical” and the more recent studies, and show that there is no particular measurement, assumption, or model parameter in the old studies that was grossly wrong. Instead, at least several effects, operating together, are likely required in order to achieve agreement between the observations and the currently standard cosmology. Most likely among these effects are: a somewhat lower lensing cross section for elliptical galaxies than assumed in the past; some loss of lensed quasars in optical samples due to extinction by the lenses; and a somewhat lower-than-standard value of $\Omega_{\Lambda}\sim 0.6$. The agreement between recent model calculations and the results of radio lens surveys may be fortuitous, and due to a cancellation between the errors in the input parameters for the lens population and the cosmology, on the one hand, and for the source population, on the other hand.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present results from an SED analysis of two lensed high-$z$ objects, the $z=6.56$ galaxy HCM6A behind the cluster Abell 370 discovered by Hu et al. (2002) and the triple arc at $z \sim 7$ behind Abell 2218 found by Kneib et al. (2004). For HCM 6A we find indications for the presence of dust in this galaxy, and we estimate the properties of its stellar populations (SFR, age, etc.), and the intrinsic ly$\alpha$ emission. From the “best fit” reddening ($E(B-V) \sim 0.25$) its estimated luminosity is $L \sim (1-4) \times 10^{11} \lsun$, in the range of luminous infrared galaxies. For the arc behind Abell 2218 we find a most likely redshift of $z \sim$ 6.0–7.2 taking into account both our photometric determination and lensing considerations. SED fits indicate generally a low extinction but do not strongly constrain the SF history. Best fits have typical ages of $\sim$ 3 to 400 Myr. The apparent 4000 Å break observed recently by Egami et al. (2004) from combination of IRAC/Spitzer and HST observations can also well be reproduced with templates of young populations ($\sim$ 15 Myr or even younger) and does not necessarily imply old ages. Finally, we briefly examine the detectability of dusty lensed high-z galaxies with Herschel and ALMA.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Period04, a reworked and extended version of Period98 (Sperl 1998) and PERIOD/PERDET (Breger 1990), is a new software package especially dedicated to the statistical analysis of large astronomical data sets containing gaps. It offers tools to extract the individual frequencies from the multiperiodic content of time series and provides a flexible interface to perform multiple-frequency fits. A review of the functions of Period04 is given.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Double-lined-eclipsing binaries are the essential systems for the measurement of stellar masses and radii. About 50-60 systems have components (mostly A-stars) for which these values are known with an uncertainty less than 1-2%. Therefore, these systems are very suitable to improve our understanding of stellar structure and evolution. In this paper, special attention is given to the assessment of the role of internal rotation of the early-type stars in selected double-lined binaries (i.e., EK Cep, PV Cas, and $\theta^2$ Tau): it is shown that adoption of rapidly rotating cores for such stars permits the models to be in very good agreement with the observational results including the apsidal advance rates.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Elemental abundance analysis are derived for the Mercury-Manganese stars HR 4817 (B8 II/III) and $\mu$ Lep (B9 IV) using CCD recorded exposures obtained at the EBASIM echelle spectrograph at the 2.1-m CASLEO (Complejo Astronómico El Leoncito) telescope in Argentina. The spectra coverage is 390-900 nm. The results are compared with previous analyses made with spectra taken using the REOSC echelle spectrograph at CASLEO, the coudé feed telescope at Kitt Peak National Observatory, and/or with the Dominion Astrophysical Observatory coudé spectrograph. As these new spectra go farther into the red and have better resolution than those obtained with the REOSC, we could make better abundance determinations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The single-lined 51.420d spectroscopic binary $\alpha$ Dra (HD 123299, Thuban, spectral type A0 III) is a slightly metal poor star. First orbital elements were obtained by Harper in 1907. Mizar A (HD 116656, spectral type A2 V) is a double-lined 20.53 d spectroscopic binary first reported by Pickering in 1890. Its orbital elements were determined by Vogel in 1901. The redetermination of the orbital elements for these two binaries used the spectrum disentangling computer code KOREL (Hadrava 1995, 1997). We present revised orbital elements based on new electronic spectra taken at the Ondřejov Observatory between 1994 and 2003.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We derived the chemical abundances in the photosphere of $\delta$ Scuti, the prototype of the class of pulsating variables, from the analysis of a spectrum obtained at the Terskol Observatory 2-m telescope with a resolution $R=52000$ and $S/N=250$. VLT and IUE spectra were also used. The abundance pattern of $\delta$ Sct consists of 49 chemical elements. The abundances of Be, P, Ge, Nb, Mo, Ru, Er, Tb, Dy, Tm, Yb, Lu, Hf, Ta, Os, Pt, and Th were not investigated previously. The lines of third spectra of Pr and Nd also are investigated for the first time. The abundances of heavy elements show overabundances with respect to the Sun up to 1 dex. The abundance pattern of $\delta$ Sct is similar to that of the Am-Fm stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The subject of gravitational lensing is now a mature discipline, with an automatic place in cosmology. The robust mass measures provided by lensing are one of the key reasons for having confidence in the standard model of structure formation. For the future, things are more challenging: the next set of interesting questions requires the measurement of small effects with non-trivial systematics. The real question will be whether lensing can overcome these problems rapidly enough that it becomes the most precise probe of the cosmological parameters, in particular the equation of state of the vacuum and its evolution.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We propose a method for detecting gravitational magnification of distant sources, like quasars, due to absorber systems detected in their spectra. We first motivate the use of metal absorption lines rather than Lyman-$\alpha$ lines, then we show how to relate the observed moments of the source magnitude distribution to the mass distribution of absorbers. In order to illustrate the feasibility of the method, we use a simple model to estimate the amplitude of the effect expected for MgII absorption lines. Our model suggests that quasars behind strong MgII absorbers are in average brightened by $-0.05$ to $-0.2$ magnitude due to magnification. One must therefore revisit the claim that, in magnitude limited surveys, quasars with strong absorbers tend to be missed due to extinction effects. In addition to constraining the mass of absorber systems, applying our method will allow for the quantification of this bias.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using an homogeneous sample of $v\sin i$ values for A-type main sequence stars (Royer et al. 2002), the equatorial velocity ($v$) distributions are determined as function of spectral class, from B9 to F2. The chemically peculiar and binary stars are discarded. These distributions of “normal” stars are discussed in terms of stellar formation and evolution, in particular the remaining bimodality observed for the earliest spectral types of the sample. We show that late B and early A-type main-sequence stars have genuine bimodal distributions of true equatorial rotational velocities probably due to the phenomena of angular momentum loss and of redistribution the star underwent before reaching the main sequence. A striking lack of slow rotators is noticed among intermediate and late A-type stars. The bimodal-like shape of their true equatorial rotational velocity distributions could be due to evolutionary effects.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a direct detection of the growth of large-scale structure, using weak gravitational lensing and photometric redshift data from the COMBO-17 survey. Deep $R$-band imaging of two $0.5\times0.5$ square degree fields is used to provide shear estimates for over 52000 galaxies; these are combined with photometric redshift estimates from our 17 band survey, in order to obtain a 3-D shear field. We discuss how theoretical models for evolving matter power spectra and correlation functions cab be used to find a best fit to this 3-D shear field. We present the detection of the evolution of the power, and measurements of the rate of evolution for $0<z<1$. We discuss future refinements which will improve the accuracy with which the effect can be measured.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

PISKUNOV: I would like to start this discussion with evolutionary aspects. There are a few recent developments both observational and theoretical. So, some might disagree and others might agree that there are many things happening concerning the pre-Main sequence evolution of early A type and Ap stars and that is what makes them different. Would anybody like to comment?To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

NOELS: How is convection suppressed in model computations?

CUNHA: We do this in two different ways. One is just to make the mixing parameter smaller and smaller. As it approaches zero we are, in e.ect, suppressing convection. The other way is simply to use the equation for radiative energy transport throughout the envelope. The results are very similar.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe the first results of a systematic spectropolarimetric survey of the coolest magnetic Ap stars, undertaken with the MuSiCoS spectropolarimeter, with the aim of clarifying the magnetic field and atmospheric characteristics of these enigmatic objects.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Weak gravitational lensing can be combined with distance information from galaxy redshifts to great effect in 3-D weak lensing. With both shear and redshift information I show how the full 3-D dark matter distribution can be reconstructed and present a first application to the COMBO-17 data-set. In addition, I describe the Jain-Taylor geometric test, taking ratios of galaxy shear at different distances, as a probe of the dark energy in the universe and present a preliminary application to COMBO-17.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We describe an ongoing programme using the FORS1 spectropolarimeter on the ESO-VLT to search for magnetic fields in Herbig Ae/Be stars. Our aim is to identify the pre-Main Sequence progenitors of magnetic Ap stars, and to trace the evolution of their magnetic fields at the earliest possible stages.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High $S/N$ high-resolution spectroscopic observations of seven bright well-known $\lambda$ Bootis stars: HD 31295, HD 91130, HD 110411, HD 125162, HD 183324, HD 192640, and HD 221756 are presented. Sharp absorption details observed in the bottoms of the Na-D lines in HD 192640 and HD 221756 do not show any radial velocity changes with an accuracy up to $1\,{\rm km\,s}^{-1}$. They are of interstellar origin. Manifestations of non-radial pulsation reported earlier in literature are observed both in the Na-D and the ${\rm H}\alpha$ line profiles. The Inglis-Teller formula was used to evaluate the electron density in the upper atmospheric layers ($\tau \sim 0.1$). The values obtained for $\log{N_e}$ are typical for normal A stars with similar effective temperatures and spectral classes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss the internal structure of stars in the mass range 1.5 to 4 $M_\odot$ from the PMS to the subgiant phase with a particular emphasis on the convective core and the convective superficial layers. Different physical aspects are considered such as overshooting, treatment of convection, microscopic diffusion and rotation. Their influence on the internal structure and on the photospheric chemical abundances is briefly described.

The role of binarity in determining the observed properties and as a tool to constrain the internal structure is also introduced and the current limits of theories of orbital evolution and of available binary datasets are discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html