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The atmospheres of chemically peculiar stars can be highly structured in both the horizontal and vertical dimensions. While most prevalent in the magnetic stars, these structures can also exist in non-magnetic stars. In addition to providing an important window to understanding the physical processes at play in these complex atmospheres, they can also be exploited to study stellar pulsations. This article reviews contributions to the session “A 3D look into the atmosphere” of the Joint Discussion “Progress in understanding the physics of Ap and related stars”. It is divided into 3 sections: “Magnetic field and surface structures”, “Pulsations in the atmospheres of roAp stars/inversions”, and “Spectral synthesis/atmospheric models”.

Ireland has a vast network of minor rural roads that are immensely important to both tourism and general amenity. However, the litter problem associated with such roads is growing steadily and is attracting adverse comment not only within Ireland but also from abroad. The purpose of this pilot project was to develop a simple methodology to measure litter density, to quantify the litter problem in a randomly selected 100 km2 area in County Wicklow, and to suggest possible remedial actions. The key recommendations focus on the removal of large litter items prior to verge and hedge mowing; a levy on beverage containers, which are the single largest littering item; the periodic removal of litter; community involvement in litter abatement and collection; and the prevention of accidental littering from vehicles and rural refuse collection points.

We have performed time series analyses on more than 4500 sets of Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) data, obtained from about 3600 guide stars in the period from August 1992 to December 1995. We discuss here a subset of 20 stars that were found to be variable at a high condence level. This subset contains all denite variables in our sample for which at least spectral type, B V ,o r Strcolors, respectively, are available. Our variability survey is characterized by comparably high photometric accuracy and high time resolution. The time base of a data set for a given guide star can range from half an hour to several days and even up to years in some cases. The elimination of scintillation noise in a space-borne experiment and the usage of the identical in- strument throughout the survey results in very homoge- neous data with a typical photometric precision of about 500 ppm, and with a best case of 50 ppm. Half of the cases discussed here are probably Sct variables, and two are eclipsing binaries. We have also found four K-type stars with a photometric period of a few hours, which is dicult to interpret as rotation. Currently, several space missions are in preparation, dedicated to high precision photometry with the goal of applying asteroseismic techniques to a signicant sam

This report does not intend to give a complete review of all the papers that appeared since the previous General Assembly but to focus on a few subjects only.

Light curves of 26 probable contact binary stars are made available, from a list of candidates with the shortest periods known. This is supplemented by sets of light curves of three previously studied systems. Photometry was obtained in the Johnson UBV, Cousins RI system. All stars but one were observed in four wavebands, either UBV RC or , depending on brightness. Tentative spectral classifications are given for 23 of the stars. Effective temperatures are derived from infrared and optical photometric indices, and from spectral types. These are generally in good agreement. The multicolor photometry, spectral typing, and estimated effective temperatures can be used to model these systems in detail. A preliminary study, based on Fourier coefficients of the light curves, suggests that all the systems are indeed eclipsing stars, with all but a handful probably in contact configurations.

We are obtaining spectra, spectral types and basic physical parameters for the nearly 3600 dwarf and giant stars earlier than M0 in the Hipparcos catalog within 40pc of the Sun. Here we report on results for 1676 stars in the southern hemisphere observed at Cerro Tololo Interamerican Observatory and Steward Observatory. These results include new, precise, homogeneous spectral types, basic physical parameters (including the effective temperature, surface gravity, and metallicity, [M/H]) and measures of the chromospheric activity of our program stars. We include notes on astrophysically interesting stars in this sample, the metallicity distribution of the solar neighborhood and a table of solar analogues. We also demonstrate that the bimodal nature of the distribution of the chromospheric activity parameter log R'HK depends strongly on the metallicity, and we explore the nature of the ``low-metallicity'' chromospherically active K-type dwarfs., 62 pages including a long table, 6 figures

This report rovers research in the field of stellar classification in the period July 1993 to June 1996. It is divided into several sections which were written by experts in each subfield. I want to thank them for their effort and cooperation. To conserve space, all references are given with only one name followed by a + sign if there are additional authors.

The meeting of the Working Group on standard stars (WG-SS) opened under the chairmanship of Corbally. Gray, as editor, gave a report on the Standard Stars Newsletter (SSN). Through a round of thanks given to Gray, it was recognized by the two dozen present that this publication is the major vehicle between WG-SS meetings for achieving its tasks, namely promoting and communicating work on standard stars. Copies of the newsletter can be downloaded from .

A search for λ Bootis stars in two OB associations, Orion OB1 and Lacerta OB1, has been carried out. One λ Bootis star has been discovered in the Orion OB1 association. In addition, nine A-type stars which appear to be slightly metal weak have been found in the two associations. The λ Bootis star is situated on the Zero-Age Main Sequence (ZAMS). The discovery of these stars strengthens the hypothesis that the λ Bootis stars are related to a short-lived evolutionary phase associated with the arrival of the star on the ZAMS

Direct electron microscopic examination confirms that short actin filaments rapidly anneal end-to-end in vitro, leading over time to an increase in filament length at steady state. During annealing of mixtures of native unlabeled filaments and glutaraldehyde-fixed filaments labeled with myosin subfragment-1, the structural polarity within heteropolymers is conserved absolutely. Annealing does not appear to require either ATP hydrolysis or the presence of exogenous actin monomers, suggesting that joining occurs through the direct association of filament ends. During recovery from sonication the initial rate of annealing is consistent with a second-order reaction involving the collision of two filament ends with an apparent annealing rate constant of 10(7) M-1s-1. This rapid phase lasts less than 10 s and is followed by a slow phase lasting minutes to hours. Annealing is calculated to contribute minimally to filament elongation during the initial stages of self-assembly. However, the rapid rate of annealing of sonicated fixed filaments observed in vitro suggests that it may be an efficient mechanism for repairing breaks in filaments and that annealing together with polymer-severing mechanisms may contribute significantly to the dynamics and function of actin filaments in vivo.

The MK spectral classification for late A-type stars is refined and the effects of rotation of spectral classification and uvby(beta) photometry for these stars are examined. It is found that, for A3 stars, the 4417/4481 A wavelength ratio produces results that are inconsistent with the Stark broadening of the H lines. It is suggested that this ratio is not useful as a luminosity criterion at any spectral type. Self-consistent sequences of narrow- and broadline standards are established. The results of the refined classification system are compared with Stromgren photometry, showing a set of low-v sin i A-type stars with anomalously large delta(c sub 1) indices for their luminosity types. It is proposed that these stars are rapid rotators seen at fairly low inclination angles. 24 refs.

On presente les indices photometriques theoriques dans des systemes de Stromgren et β pour les grilles de Kurucz publiees ou non. Ces indices ont ete places dans des systemes standards en utilisant des distributions d'energie UV et visuelles des standards pgotometriques secondaires

The star FO Vir, a recently discovered eclipsing binary with a period of 0.776 days, has been observed photometrically and spectroscopically. Light-curve and line-profile synthesis shows that FO Vir is semidetached with a mass ratio of 0.15 + or - 0.02. The A7 V primary component very nearly fills its Roche lobe. Radial velocities from the observed and synthesized profiles have been measured by cross correlation. The theoretical radial-velocity curve fits the observations well, to yield a mass of 1.9 + 0.9 or - 0.6 solar mass for the primary and 0.29 + 0.08 or - 0.06 solar mass for the secondary. The mean density is 0.17 + or - 0.02 g/cu cm for the primary, 0.33 + or - 0.03 g/cu cm for the secondary, with log g about 3.9 and Mv about 1.7 for the primary. This suggests the primary has evolved off the zero-age main sequence, while the secondary has a density that shows that for its mass it is highly evolved. The period and mass ratio are typical of the more extreme A-type W UMa systems, which suggests that FO Vir will evolve into a contact binary of this type. Short-period semidetached binaries may be themore » progenitors of at least some W UMa systems. 46 references.« less