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

DG Leo is a spectroscopic triple system showing $\delta$ Scuti type photometric and spectroscopic variations. The three components have nearly equal masses but different chemical compositions in the outer layers. All three are potential pulsators. Frequency analyses of the photometric data were carried out using various methods. These global results together with those of the spectroscopic analysis permit us to discuss of the behaviour of each component with respect to pulsation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a novel method, based on the Doppler imaging inversion technique, which tries to construct a two-dimensional ‘image’ of the pulsation velocity field using time series observations of stellar spectra. This method is applied to study the geometry of nonradial oscillations in the roAp star HR 3831. The image of pulsational perturbations at the surface of this star is the first stellar pulsation map derived without assuming the spherical harmonic formalism. Our Doppler reconstruction directly demonstrates an alignment of the roAp pulsations with the stellar magnetic field axis. It also reveals a significant distortion of the dominant oblique $\ell=1$ oscillation mode by the stellar magnetic field. This first detailed characterization of the magnetic and rotation effects on pulsations opens possibilities for the direct testing of recent theories of magnetoacoustic oscillations in roAp stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The existence of Maia variables has been in dispute since 1955. They are supposed to be located between the blue edge of the classical instability strip and the red border of the slowly pulsating B stars, hence in a domain of the HRD where no excitation mechanism for pulsation is yet known. But luminosity variations were discovered in time series of $\alpha$ Draconis, an A0III Maia candidate star, with a period of about 53 minutes and an amplitude of less than 0.002 mag. Spectroscopic time series indicate radial velocity variations with the same period and an amplitude of about $40{\rm m\,s}^{-1}$. Alpha Dra is a single-lined spectroscopic binary with an orbital period of 51.4 days and a distance between the components of about 0.46 AU. Tidal interaction may therefore be responsible for pulsation. If true, the pulsation amplitude should be modulated with the orbit as is indeed indicated by recent observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In addition to revealing spherical harmonic degrees, $\ell$, of excited modes, pulsational amplitudes and phases from multicolour photometry and radial velocity data yield valuable constraints on stellar atmospheric parameters and on subphotospheric convection. Multiperiodic pulsators are of particular interest because each mode yields independent constraints. We present an analysis of data on the twelve modes observed in FG Vir.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Based on a preliminary analysis of 3 nights of high-dispersion spectral observations of HD 101065 (Przybylski's star) obtained on the ESO 3.6-m telescope + HARPS we find rapid multiperiodic radial velocity oscillations of at least three pulsation modes. The detailed analysis of the frequency space and probable splitting based on 4 nights of data will be given later.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 study we use preliminary atmospheric parameters for the A0 Ib supergiant $\eta$ Leo ($T_{\rm eff}, \log g$ and microturbulent velocity) to provide initial estimates of the elemental abundances from S II, Ti II, Cr II, Fe I and Fe II lines by using spectrograms with a two pixel resolution of 0.072 Å and signal-to-noise ratio $\ge$ 200 taken at the Dominion Astrophysical Observatory.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using Kurucz's ATLAS9 model atmospheres I performed LTE fine analyses of the supergiants 4 Lac and $\nu$ Cep. The spectra were obtained at 1.22-m telescope of the Dominion Astrophysical Observatory (DAO) by Saul J. Adelman. The atmospheric parameters were derived using the wings of ${\rm H}\beta$ and ${\rm H}\gamma$ profiles for each star, and from Fe I/II, Fe II/III, and Si II/III equilibria for 4 Lac, and from Fe I/II and Cr I/II equilibria for $\nu$ Cep. A microturbulence of $2.7\,{\rm km\,s}^{-1}$ for 4 Lac was found from Fe II lines while a mean value of $5.2\,{\rm km\,s}^{-1}$ for $\nu$ Cep from Cr II, Ti II and Fe II lines. The rotational and macroturbulent velocities are, respectively, $14\pm2{\rm km\,s}^{-1}$ and $15\pm 2\,{\rm km\,s}^{-1}$ for 4 Lac, and $26 \pm 2{\rm km\,s}^{-1}$ and $12 \pm 2{\rm km\,s}^{-1}$ for $\nu$ Cep. Their He, CNO and light element abundances are solar or overabundant while their iron peak and heavy element abundances are solar or underabundant. The derived results show that 4 Lac has nuclearly processed matter in its photosphere while $\nu$ Cep does not.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The progenitors of magnetic white dwarfs are believed to be magnetic Ap and Bp stars because the fields in these stars are structured and are present in the stellar core. As in Ap/Bp stars the magnetic fields in white dwarfs are, in most cases, dipolar or quadrupolar with various offsets. Although the present space density of Ap/Bp progenitors would be sufficient to account for the density of magnetic white dwarfs in young populations such as found in the Palomar-Green survey, we show that it would be insufficient to generate the density of known magnetic white dwarfs in the older solar neighborhood. Assuming magnetic flux conservation during the final stages of evolution, we find that Ap/Bp stars would evolve into white dwarfs with magnetic fields exceeding $10^7$ G, assuming a minimum polar field of 200 G in Ap/Bp stars, thereby leaving many magnetic white dwarfs with lower fields without likely progenitors.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

We report irregular changes in the line profiles of Deneb, and suggest that they represent part of the mechanism causing the stellar wind.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We have a project, under the aegis of the Nearby Stars (NStars)/Space Interferometry Mission Preparatory Science Program to obtain the spectra, the spectral types, and, where feasible, the basic physical parameters for the 3600 dwarf and giant stars earlier than M0 within 40 parsecs of the Sun. There are 66 B-to-early-F stars among the first 664 stars analyzed in the Northern hemisphere, and 38 of the same among a similar number of Southern hemisphere stars. With these we can start looking at the statistics of Ap, Am, $\lambda$ Boötis, and other A-type stars for a volume-limited sample, and we can find out just how well we know our neighbors. The project's data are available on our website, http://stellar.phys.appstate.eduTo search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A cross-dispersed spectrophotometer with a back-illuminated uv-coated CCD detector and its automated 0.5-m telescope at the Fairborn Observatory, Washington Camp, AZ now under construction, should begin scientific observations in the Spring of 2005. The Citadel ASTRA (Automated Spectrophotometric Telescope Research Associates) Telescope will be able to observe Vega the primary standard, make rapid measurements of the naked-eye stars, use 10 minutes per hour to obtain photometric measurements of the nightly extinction, and obtain high quality observations of $V = 10.5$ mag. stars in an hour. The approximate wavelength range is $\lambda$ 3300-9000 with a resolution of 14 Å in first and 7 Å in second order. Filter photometric magnitudes and indices will be calibrated in part for use as quality checks.

First a grid of secondary standards will be calibrated differentially with respect to Vega. They will also be used to find the nightly extinction. The candidates were selected from the most stable bright secondary stars of the grating scanner era, the least variable main sequence B0-F0 band stars in Hipparcos photometry, and metal-poor stars. Continued measurements of secondary stars will be used to improve the quality of the secondary standard fluxes. Science observations for major projects such as comparisons with model atmospheres codes and for exploratory investigations should also begin in the first year of scientific observations. The ASTRA team realizes to deal with this potential data flood that they will need help to make the best scientific uses of the data. Thus they are interested in discussing possible collaborations. In less than a year of normal observing, all isolated stars in the Bright Star Catalog that can be observed can have their fluxes well measured. Some A star related applications are discussed.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

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