%R 1995A&AS..112....1D
%J-7
%A Di Martino M., Dotto E., Cellino A., Barucci M.A., Fulchignoni M.
%T Intermediate size asteroids: Photoelectric photometry of 8 objects.
%F 1995.06.30
%B In this paper we present the results of photometric observations performed from 1984 until 1992 with the 0.5-m and 1-m telescopes of the European Southern Observatory (La Silla, Chile), and the 1.5-m telescope of the Osservatorio Astronomico di Bologna (Italy), in order to increase the available data sample of intermediate size asteroids (diameter included between 80km and 150km). We obtained a total of 26 single night lightcurves and the first determination of the
synodical rotational period of six asteroids: 117 Lomia (P_syn_=9.127h), 212 Medea (P_syn_=10.12h), 276 Adelheid (P_syn_=6.328h), 530 Turandot (P_syn_=10.77h), 705 Erminia (P_ syn_=7.22h), and 1031 Arctica (P_syn_=51h). For 431 Nephele the amplitude of the light variation of the obtained lightcurves is negligible and does not allow any determination of the rotational period. For 213 Lilaea we have determined a synodical rotational period of 8.045h, which is a little bit
different from that published by Zeigler (1987). We have also determined the U-B and B-V color indices for six of the observed asteroids.
%K minor planets, asteroids

%R 1995A&AS..112....9L
%J-11
%A Loden L.O., Sundman A.
%T Note on the radial velocities of 10 southern stars.
%F 1995.06.30
%B Echelle spectrograms of the stars HD 55857, 57219, 62623, 83058, 84400, 86087, 86523, 89461, 90898, 96446 have been obtained in 1991 as part of an investigation of stars previously classified as both chemically peculiar and high luminosity B and A stars. Radial velocity measurements for HD 83058, 84400 and 86087 are internally discordant and should be repeated. In the case of HD 55857, 57219, 62623 and 96466 the results are in fair agreement with earlier measurements but
for HD 86523 our result is substantially different from the earlier ones. For HD 89461 and 90898 no comparison with other sources was available. With no further observational opportunities in view (due to increasing demand on telescopes), these preliminary results are presented here.
%K stars: fundamental parameters; chemically peculiar - binaries: spectroscopic

%R 1995A&AS..112...13G
%J-34
%A Garcia-Vargas M.L., Bressan A., Diaz A.I.
%T Evolutionary models for giant extragalactic HII regions at different metallicities.
%F 1995.06.30
%B We present theoretical evolutionary models for ionizing star clusters and their associated giant HII regions up to an age of 5.4Myr and metallicities between 1/20 and 2.5 times solar. These young clusters can provide the high energy photons needed to keep the regions ionized. We discuss in some detail the Wolf-Rayet and red supergiant phases, sometimes present in the early stages of the evolution of a star cluster. The spectral features characteristic of these stars, when
detected and measured on the spectra of giant extragalactic HII regions (GEHR), can be used to constrain the age of the ionizing stellar population. The emergent ionizing continua of the clusters are used as input for the photoionization code CLOUDY to obtain the corresponding emission line spectra in the optical and infrared ranges. The effect of the metallicity is taken into account in the stellar evolution and atmosphere models as well as in the nebular gas producing a
consistent set of models. These models can provide estimates of the mass, age and metallicity of the dominant stellar population ionizing a given GEHR solely from the analysis of its optical emission line spectrum.
%K HII regions - stars: early - type; Wolf-Rayet; evolution - galaxies: ISM

%R 1995A&AS..112...35G
%J-70
%A Garcia-Vargas M.L., Bressan A., Diaz A.I.
%T Predicted emission lines from giant HII regions ionized by aging star clusters.
%F 1995.06.30
%B We have computed theoretical models of the emission line spectra of giant extragalactic HII regions (GEHR) in which a single star cluster is assumed to be responsible for the ionization. Ionizing clusters, of different masses and metallicities, were constructed assuming that they formed in a single burst and with a Salpeter Initial Mass Function. Their evolution was then followed in detail up to an age of 5.4Myr after which they lack the high energy photons needed to keep
the regions ionized. The integrated spectral energy distribution of every cluster has been computed for a set of discrete ages representative of relevant phases of their evolution and have been processed by the photoionization code CLOUDY, in order to obtain the corresponding emission line spectra of the ionized gas at optical and infrared wavelengths. A wide range of initial compositions, spanning from about 1/20 (Z=0.001) to 2.5 solar (Z=0.05), and total masses, between
about 1-6x10^4^M_{sun}_ has been considered. Gas and stars are assumed to have the same metallicity and this has been taken into account both in the stellar evolution and atmosphere models and in the nebular gas producing a consistent set of models. In this paper we present the synthetic emission line spectra of the ionized regions which are discussed in detail in Garcia-Vargas et al. (1995).
%K HII regions - stars: evolution - galaxies: ISM

%R 1995A&AS..112...71B
%J-88
%A Bonatto C., Bica E., Alloin D.
%T Ultraviolet spectral evolution of star clusters in the IUE library.
%F 1995.06.30
%B The ultraviolet integrated spectra of star clusters and H II regions in the IUE library have been classified into groups based on their spectral appearance, as well as on age and metallicity information from other studies. We have coadded the spectra in these groups according to their S/N ratio, creating a library of template spectra for future applications in population syntheses in galaxies. We define spectral windows for equivalent width measurements and for continuum
tracings. These measurements in the spectra of the templates are studied as a function of age and metallicity. We indicate the windows with a strong metallicity dependence, at different age stages.
%K galaxies: Magellanic Clouds, star clusters - Galaxy: globular clusters - stars: evolution - ultraviolet: stars

%R 1995A&AS..112...89P
%J-93
%A Picard A., Johnston H.M.
%T Astrometry of 19 globular clusters.
%F 1995.06.30
%B We present accurate positions for the center of 19 globular clusters, 8 of which are known to contain X-ray sources and/or pulsars. The positions are based on a new centroiding algorithm applied to CCD images of the clusters. The fundamental astrometry is performed with plates from the ESO Schmidt telescope, using the Hipparcos Input Catalogue as a list of primary astrometric standards.
%K globular cluster - astrometry

%R 1995A&AS..112...95C
%J-98
%A Corradi W.J.B., Franco G.A.P.
%T uvby{beta} photometry of 1017 stars earlier than G0 in the Centaurus-Crux-Musca-Chamaeleon direction.
%F 1995.06.30
%B Stroemgren uvby{beta} photometry has been collected for a total of 1017 stars earlier than G0 lying in an area of the sky containing the Southern Coalsack, the Musca, and the Chamaeleon dark clouds. The targets were selected from the SAO star catalog, and the results, which are only available in electronic form at the CDS, give V, b-y, m_1_, c_1_, and {beta} on the standard systems, with overall rms errors for one observation of one star of 0.008mag , 0.004mag , 0.006mag ,
0.009mag , and 0.011mag , respectively. The observational data introduced here is aimed for an investigation of the colour excess distribution in direction to the mentioned dark clouds as well as to the interstellar medium surrounding them.
%K interstellar medium: clouds: Southern \object{Coalsack}; \object{Chamaeleon} - ISM: dust, extinction - stars: distances

%R 1995A&AS..112...99L
%J-121
%A Leinert C., Vaeisaenen P., Mattila K., Lehtinen K.
%T Measurements of sky brightness at the Calar Alto Observatory.
%F 1995.06.30
%B We report measurements of the sky brightness at the Calar Alto Observatory during 18 moonless nights in the years 1989, 1990, 1991, and 1993. Most of the measurements were performed in eight intermediate band filters between 350nm and 820nm. A set of measurements was obtained in the broad band UBVRI filters during three nights in 1990. Typically 10 to 20 readings were obtained each night for one or two fixed positions (fixed in {alpha}, {delta}), selected to be free of
stars down to a limiting magnitude of about B=20. The sky brightnesses were calibrated using standard stars. We discuss the sky brightness variations both during individual nights and from year to year and compare the observed sky brightnesses to measurements from other observatory sites. We have found that the long-term variations are well correlated with the solar activity, for which the 10.7cm radio flux is used as a measure.
%K atmospheric effects - site testing

%R 1995A&AS..112..123V
%J-124
%A Vaz L.P.R., Clausen J.V., Gimenez A., Helt B.E., Jensen K.S.
%T Four-colour photometry of eclipsing binaries. XXXA. Light curves of LZ Centauri.
%F 1995.06.30
%B Complete uvby light curves of the detached double-lined early B-type eclipsing binary LZ Centauri are presented. They contain 916 points in each colour and were obtained 1982-84. A detailed photometric analysis based on these observations and on new spectroscopic material will be published separately (Vaz et al. 1995).
%K stars: binaries: eclipsing - stars: individual: \object{LZ Cen} - stars: fundamental parameters

%R 1995A&AS..112..125H
%J-142
%A Hainaut-Rouelle M.-C., Hainaut O.R., Detal A.
%T Lightcurves of selected minor planets.
%F 1995.06.30
%B We present 81 photometric lightcurves of 36 minor planets observed in the V and B bands at the ESO 50 cm telescope at La Silla (Chile). These asteroids were selected preferentially in order to improve their ecliptic longitude coverage in view of pole determinations and lightcurve inversions. We also give some first photometric observations and/or rotational period for several asteroids.
%K asteroids

%R 1995A&AS..112..143H
%J-149
%A Henning T., Begemann B., Mutschke H., Dorschner J.
%T Optical properties of oxide dust grains.
%F 1995.06.30
%B In this paper, we present the optical properties of a series of well-characterized metal oxides (Fe_x_ Mg_1-x_O, x=1.0, 0.9, 0.8, 0.7, 0.5, 0.4) in the wavelength range from 200nm to 500{mu}m. A number of oxygen-rich stars show circumstellar dust features between 10 and 14{mu}m and around 19{mu}m which cannot be explained by ordinary cosmic silicates but may be modelled by a mixture of aluminium oxide and iron-magnesium oxides. Calculated absorption spectra for small
spheres show one vibrational band in the range from 19.9{mu}m (FeO) to 17.7{mu}m (Fe_0.4_ Mg_0..6_O) in the Rayleigh limit. The absolute peak values of the oxide absorption bands are more than a factor of two larger than the 18{mu}m band of amorphous silicates, indicating that a small admixture of oxides can change the 18{mu}m/10{mu}m band ratio dramatically. The near-infrared opacity of the iron-rich oxides is of comparable magnitude to that of Fe_3_ O_4_. Therefore,
small amounts of iron-rich oxides in addition to silicates raise the absorbance in this spectral range in a very efficient way.
%K dust, extinction - infrared: stars; ISM: lines and bands - circumstellar matter - stars: AGB: post-AGB - methods: laboratory

%R 1995A&AS..112..151P
%J-161
%A Peng J.F., Pradhan A.K.
%T Theoretical diagnostics of ultraviolet and infrared spectral emission from boron-like ions.
%F 1995.06.30
%B Theoretical analysis of line intensities from transitions in boron-like ions, C II, N III, O IV, Ne VI, Mg VIII, Al IX, Si X, and S XII, is presented using new atomic data. Possible temperature and density diagonostics are investigated. Certain line ratios of UV lines are shown to be especially sensitive to either the electron temperature or the electron density and should be useful in the determination of these parameters; selected examples are given. Highly charged
B-like ions should serve as effective coolants through electron impact excitation of the ground state fine-structure transition ^2^P^0^_1/2_-^2^P^0^_3/2_ observed in the infrared. The IR line is expected to be strong in a variety of sources such as H II regions, AGN's and QSO's. Cooling rates for the IR transitions are tabulated as functions of temperature and density and applications to the abundance determination of elements are discussed. Laser action due to population
inversion in the metastable ^2^P^0^_3/2_ level in B-like C, N, O, Ne and Mg ions is also discussed.
%K ultraviolet: general - infrared: general - atomic processes - galaxies: nuclei - HII regions

%R 1995A&AS..112..163A
%J-171
%A Ageorges N., Monin J.-L., Desbat L., Tessier E.
%T Phase and image reconstruction from interferometric imaging: Integration of the phasors.
%F 1995.06.30
%B We present a new approach of a phase recovery method derived from the Knox-Thompson one, and used to reconstruct images blurred by the atmospheric turbulence. We rebuild the phase of the visibility whose main value contains discontinuities due to random phase shifts induced by the turbulence. The method presented in this paper is an upgrade of the one described by Monin et al. (1992) who computed the average of spatial phase gradients. We now work on integration of the
phasors gradients exp(i{nabla}{phi}), computing the average phasor components of the cross-spectrum of the visibility to reconstruct the original phase. We discuss the implied hypothesis and the advantage of our new approach. We present results on simulated images which visibility phases have been distorted using a model of atmospheric perturbed wavefronts, as well as an application on real speckle data.
%K atmospheric effects - methods: data analysis - methods: numerical - techniques: image processing - techniques: interferometric

%R 1995A&AS..112..173B
%J-178
%A Borovicka J., Spurny P., Keclikova J.
%T A new positional astrometric method for all-sky cameras.
%F 1995.06.30
%B All-sky photographs, used in meteor astronomy, need a special transformation formulae for converting the plate coordinates to celestial coordinates. An improved form of these formulae is presented. It includes a new radial projection function and the influence of the inclination of the plate from the plane perpendicular to the optical axis. The method then enables to achieve the precision near the theoretical limit simultaneously for the entire visible hemisphere. About 15
reference stars spread on the whole sky are needed. The meaning of the individual reduction constants is explained in detail. Practical hints for using the method and numerical examples are given.
%K astrometry - meteors - methods: data analysis

%R 1995A&AS..112..179M
%J-189
%A Murtagh F., Starck J.-L., Bijaoui A.
%T Image restoration with noise suppression using a multiresolution support.
%F 1995.06.30
%B In Starck & Murtagh, 1994 (SM94), it was shown how noise suppression could be built into widely-used image restoration methods, such as the Richardson-Lucy method. Arising from this work, two issues are resolved in the present paper. Firstly SM94 suppressed noise, based on the supposition that the input image could be considered as a realization of a Gaussian distribution. In this paper, noise suppression using a model based on Poisson noise and additive Gaussian read-out
noise is described. Secondly, SM94 found problems in regard to photometric accuracy when suppressing noise. A novel multiresolution method is described here which avoids this problem. The new version of the algorithm is applied to simulated images of point sources and an elliptical galaxy. In both cases the results obtained are compared to the "truth" images, i.e. the unblurred, noise-free images from which the degraded input images were constructed.
%K techniques: image processing - method: data analysis

%R 1995A&AS..112..191F
%J-199
%A Fensl R.M.
%T Line profile modelling and spatial integration grids.
%F 1995.06.30
%B For numerically reliable line profile modelling as required in a number of astrophysical applications, the distribution of the spatial grid points has to meet certain conditions. In the observer's system macroscopic velocity fields and/or non-homogeneous magnetic field geometries lead - via Doppler shift, magnetic field strength and direction - to local profiles which usually exhibit a non-linear dependency on the position on the visible hemisphere. The simple recipe of
using surface elements of equal size and/or of raising the number of grid points as employed by most researchers in the field of line profile modelling clearly does not make use of the known variations of line profile shapes with position, leading to a waste of computer resources at best, to serious numerical errors at worst. Following the ideas of Stift (1985) this paper proposes a method which leads to a distribution of the spatial integration points which is near optimum
in the sense that it ensures an upper limit to the variation in the quantities to integrate using an almost minimum number of points. Its design is based on the requirement of a constant change in line intensity between any two adjacent integration points. Simple cases that can be treated analytically illustrate the potential savings possible compared to conventional methods (for rotating and (non-)radially pulsating stars savings of a factor of 6 in CPU time can be achieved)
and the fact that (nearly) optimum grids never consist of equally sized surface elements. Finally the flexibility and power of the present approach is illustrated by means of Stift's (1975) eccentric tilted dipole model.
%K line: profiles - methods: analytical - methods: numerical