%R 1994A&AS..108..253Z
%J-270
%A Zheng J.-Q.
%T Orbital changes of Oort cloud comets due to strong planetary influences.
%F 1994.11.15
%B When an Oort cloud comet comes into the planetary region its orbit might be perturbed by planets so that the comet becomes a short period comet. The dynamical transfer of Oort cloud comets into short period comets is considered in this paper. By using the few body problem integrations with K-S regularization method, we have calculated a large number of initial parabolic orbits with different inclinations and different perihelion distances. We also calculated the
cross-sections and obtained the distributions of new inclinations and new perihelion distances for given energy changes in order to explain the orbital features of short period comets.
%K celestial mechanics - comets

%R 1994A&AS..108..271C
%J-278
%A Caulet A., Hook R.N., Fosbury R.A.E.
%T Measurements of the sky background using the HST Faint Object Camera.
%F 1994.11.15
%B The results of a novel method of measuring the three dominant components of the sky brightness from the Hubble Space Telescope orbit are reported. The shadows cast by an occulting finger in the Faint Object Camera (FOC), when the field is dispersed with an objective prism, are separated into three features: the geocoronal Ly{alpha} and neutral oxygen airglow emission lines in the far ultraviolet, and the zodiacal light continuum above 3000 A. These are measured as
functions of the relevant angles in the spacecraft-earth-sun geometry. The measurements are compared with predictions derived from models. Satisfactory agreement is found when the revised f/96 detector quantum efficiency of the FOC is used. The zodiacal light is well within the expected range of 70-210 S10 units for the observed ecliptic coordinates. The Ly{alpha} emission background is 25% lower than expected for all solar zenith distances. There is an excess of OI emission,
by a factor of two above the predictions. There is a weak correlation between the Ly{alpha} emission and the target zenith distance.
%K diffuse radiation - earth - interplanetary medium - methods: observational

%R 1994A&AS..108..279J
%J-285
%A Jackson B.V., Buffington A., Hick P.L., Kahler S.W., Webb D.F.
%T A spaceborne near-Earth asteroid detection system.
%F 1994.11.15
%B We have designed a Solar Mass Ejection Imager (SMEI) to image transient heliospheric features from Earth orbit over the entire sky every 90 minutes. The instrument is designed to detect changes on this time scale in the signals from sunlight Thomson-scattered from electrons at a brightness level of tenth magnitude per square degree of sky. We explore the possibility of using such an instrument to detect asteroids passing near the Earth. We estimate that SMEI will detect at
least 13 asteroids per year over ~12m in radius.
%K instrumentation: photometers - methods: data analysis - meteoroids - minor planets

%R 1994A&AS..108..287V
%J-340
%A Verner D.A., Barthel P.D., Tytler D.
%T Atomic data for absorption lines from the ground level at wavelengths greater than 228A.
%F 1994.11.15
%B We list wavelengths, statistical weigths and oscillator strengths for 2249 spectral lines arising from the ground states of atoms and ions. The compilation covers all wavelengths longward of the He II Lyman limit at 227.838A and all the ion states of all elements from hydrogen to bismuth (Z=83) for which reliable data are known. We assign experimental wavelengths to 1086 lines which have oscillator strengths calculated in the Opacity Project, and add 1163 lines which have
critically evaluated oscillator strengths from previous compilations. The presented data are to be used for quasar absorption spectra interpretation. We use solar abundances to calculate the expected relative strengths of all absorption lines, and list separately the strongest lines above 228A expected in QSO absorption systems, many of which are listed here for the first time. The great majority of strong lines expected in quasar spectra are at {lambda}<912A. We also list
the strongest absorption lines of various ions without wavelength restriction.
%K atomic data - quasars: absorption lines - ultraviolet: general

%R 1994A&AS..108..341M
%J-358
%A Marquez A., Schuster W.J.
%T uvby-{beta} photometry of high-velocity and metal-poor stars. VII. Ages of halo and thick-disk field stars.
%F 1994.11.15
%B Ages have now been determined for the turn-off stars of our two uvby-{beta} catalogues. As in Paper III, polynomial fittings have been used to interpolate the isochrones of VandenBerg & Bell (1985) in the c_0_,(b-y)_0_ plane, and as in Paper V, graphical interpolations for the isochrones of VandenBerg (1985) and of Bergbusch & VandenBerg (1992) in the {delta}M_V_, log T_eff_ plane. The interstellar color excesses, E(b-y), and photometric metallicities, [Fe/H], of the stars
have been determined using our previous photometric calibrations. Membership of the stars in the different stellar populations has been determined using the V_rot_,[Fe/H] diagram, and Galactic orbits calculated for the halo stars employing the Galactic mass distribution of Allen & Santillan (1991). Combining with previous work and cleansing the samples of the more obvious binary-star contamination, ages remain for 71 halo stars and for 296 "high-velocity disk" stars of which
24 are from the nearly pure thick-disk sample of Paper VI. Our previous conclusions are mostly confirmed that there is good evidence for a cosmic age scatter of several Gyr within the halo field stars and that there is considerable overlap between the ages of the halo stars and the older disk stars. However, the previously found metallicity-age correlation for the halo field stars has mostly disappeared. In addition, evidence is found that the inner part of the halo is older
and has a smaller age dispersion than the outer part, and that, on the average, the thick disk is only 1-2 Gyr younger than the halo having a mean age similar to that of the outer halo. These results are discussed and interpreted in terms of various formation scenarios for the thick disk, dual-halo models, and "inside-out" evolutionary schemes for the Galaxy proposed in the literature.
%K Galaxy: evolution; stellar content - stars: Population II

%R 1994A&AS..108..359G
%J-375
%A Ginestet N., Carquillat J.M., Jaschek M., Jaschek C.
%T Spectral classifications in the near infrared of stars with composite spectra. I. The study of MK standards.
%F 1994.11.15
%B Up to now the spectral classifications of the cool components of composite spectra obtained in the 3800-4800A wavelength region have been very disparate. These disparities are due to the fact that the spectra of the evolved cool component are strongly veiled by that of the hotter dwarf component, which makes a classification very difficult. We propose to study these systems in the near infrared (8380-8780A). In this spectral domain the magnitude difference between the
spectra of the components is in general sufficiently large so that one observes practically only the spectrum of the cool component. In this first paper we provide, for a sample of MK standards, the relations between the equivalent width (W_{lambda}_ ) of certain lines and the spectral classifications. For the cool G, K and M type stars, the lines considered are those of the calcium triplet (Ca II 8498, 8542 and 8662), of iron (Fe I 8621 and 8688), of titanium (Ti I 8426 and
8435) and of the blend {lambda}8468. The use of certain line intensity ratios permits, after eliminating partially the luminosity effects, a first approach to the spectral type. For the hotter stars of types O, B, A and F we study the behavior of the hydrogen lines (P12 and P14), the calcium lines (Ca II 8498 and 8542) as well as those of the oxygen (O I 8446). The latter line presents a very characteristic profile for stars of low rotation and therefore in Am stars, which
are frequently found among the composite spectrum binaries. Among the cooler stars of our sample, only 6% present real anomalies with respect to the MK classifications. This result is very encouraging for undertaking the classification of a sample of composite spectra. The spectra were taken at the Observatoire de Haute-Provence (OHP) with the CARELEC spectrograph at the 193 cm telescope, with a dispersion of 33 A/mm.
%K binaries: spectroscopic - stars: classification - infrared: stars

%R 1994A&AS..108..377S
%J-394
%A Szatmary K., Vinko J., Gal J.
%T Application of wavelet analysis in variable star research. I. Properties of the wavelet map of simulated variable star light curves.
%F 1994.11.15
%B A type of the relatively new time-frequency method, the wavelet analysis is studied. Some results of testing this method are presented. The test data series were defined so that they show similarities with the light variations of variable stars. The effects of observational noise and irregularities in data sampling are pointed out. The wavelet analysis seems to be a suitable method for detecting the local behaviour of the light curves, e.g. phase jump or mode switching.
The investigation of time-dependent phenomena, e.g. amplitude or frequency modulation, is more available than in the case of standard Fourier analysis. In order to interpret the real wavelet maps of variable stars it is necessary to take into account the properties of the method presented by similar tests.
%K methods: data analysis - stars: oscillations; variables

%R 1994A&AS..108..395A
%J-402
%A Adanti S., Battinelli P., Capuzzo-Dolcetta R., Hodge P.W.
%T A new automatic identification technique for OB associations in unresolved galaxies.
%F 1994.11.15
%B We present a new automatic technique based on Principal Component Analysis and Cluster Analysis, with the aim of its application to the identification of those clumps in unresolved galaxies which likely represent regions of star formation. We test the method by applying it to the galaxy M 31, for which there are already several sets of identifications of OB associations based on multi-colour images of resolved stars. We use small-scale digital images of M 31 and compare
the associations that we detect from these unresolved data with previously-published large-scale data, finding a rather good agreement. We obtain a strict agreement of our identification with the most compact associations of the original van den Bergh (1964) identification. We then apply the technique to CCD images of the more distant spiral galaxy NGC 2903 and identify 68 OB association candidates.
%K methods: data analysis - galaxies: individual: \object{M 31} - galaxies: individual: \object{NGC 2903} - galaxies: star clusters

%R 1994A&AS..108..403J
%J-408
%A Jonch-Sorensen H.
%T CCD uvby{beta} photometry of faint stars. I. Observations and reductions.
%F 1994.11.15
%B An observational programme involving simultaneous CCD- and photoelectric uvby{beta} photometry has been carried out using the two Danish telescopes at La Silla. In order to derive reliable astrophysical parameters for F dwarfs at distances of several kpc final accuracies better than 0.015mag for each magnitude are needed for faint stars. High accuracy requires careful preprocessing and data handling and the requested accuracy is now obtained for stars as faint as V=~18mag
using the procedure described in this paper. A common robust CCD instrumental system is established and the subsequent transformation to the standard system is performed using a set of faint secondary standards observed in the photoelectric programme. Photoelectric photometry for a number of calibration stars in the CCD frames is also published. These stars have up to 11 observations each and may be included in the preliminary sample of secondary standards that has emerged
from the combined programme.
%K techniques: photometric

%R 1994A&AS..108..409B
%J-415
%A Bi H., Boerner G.
%T When does the Richardson-Lucy deconvolution converge?
%F 1994.11.15
%B We propose a simulation-based bootstrap method to access global significance levels of deconvolution models in the Richardson-Lucy and other iterative restoration algorithms that converge locally. These significance levels allow one to check at each iterative step how good the model is and when iterations can be stopped. Adding more iterations in the deconvolution improves the fitting but is very slow at later time; while too much entropy or smoothness will be lost in the
models. A good deconvolution model should firstly have a significance level as high as possible (>=20%), and secondly, be as smooth as possible. We have used two examples to illustrate how such models can be derived in practice. We point out that maximizing the sum of the likelihood of fitting and a priori entropy does not guarantee an acceptable significance level for the resulting model. If one's a priori knowledge is too poor, the model may not be able to fit the data at
a reasonable significance level. Instead, a maximum-entropy-like iterative restoration algorithm can be performed later by acquiring a priori knowledge from the Richardson-Lucy restoration. However, this is necessary only when it does increase the levels significantly.
%K methods: data analysis - methods: statistical - techniques: image processing

%R 1994A&AS..108..417A
%J-431
%A Allard N.F., Koester D., Feautrier N., Spielfiedel A.
%T Free-free quasi-molecular absorption and satellites in Lyman-alpha due to collisions with H and H^+^.
%F 1994.11.15
%B We present new theoretical calculations of the total line profiles of Lyman {alpha} including both red and blue far wings. All the transitions involved due to H-H and H-H^+^ collisions are taken into account and weighted by their dipole transition moments. The resulting profile shows a number of satellite features, at least two of which have been observed in ultraviolet spectra of hydrogen-rich white dwarfs.
%K line: profiles - stars: white dwarfs - atomic data

%R 1994A&AS..108..433A
%J-440
%A Andrievsky S.M., Kovtyukh V.V., Usenko I.A., Klochkova V.G., Galazutdinov G.A.
%T Chemical composition of selected double-mode Cepheids and the P_1_/P_0_ - [Fe/H] relation.
%F 1994.11.15
%B We present the results of the detailed spectroscopic investigation of three double-mode Cepheids: EW Sct, VX Pup and BQ Ser. The abundance analysis has shown: (1) Carbon is deficient (the abundance normalized to the iron content with respect to the solar value). (2) This carbon deficiency is accompanied by nitrogen overabundance and normal oxygen content. (3) {alpha} - and iron group elements with little exception show solar ratio [M/Fe]. (4) The heavy elements in EW Sct
are underabundant. (5) Normal iron abundance for EW Sct ([Fe/H]=-0.08) and metal deficiency for VX Pup ([Fe/H]=-0.39) and BQ Ser ([Fe/H]=-0.36) strongly support the existence of a P_1_/P_0_-metallicity relation, as first discussed in work of Andrievsky et al. (1993).
%K stars: abundances - stars: variables: Cepheids - stars: individual: EW Sct, VX Pup, BQ Ser

%R 1994A&AS..108..441M
%J-446
%A Malyuto V.
%T A new approach to calibrating the Stroemgren photometric system in terms of metal-to-hydrogen ratio.
%F 1994.11.15
%B To improve the calibration of the indices of the Stroemgren photometric system in terms of high-resolution spectroscopic [Fe/H] values, new algorithms have been tested. The statistical method of stepwise linear regression has been successfully applied to the data sample of F-type stars with the aim of defining the refined calibration equations 'spectroscopic [Fe/H] versus the (b-y), m_1_, and c_1_ photometric indices, and their combinations'. To enlarge the sample of
calibration stars, we have added to the heterogeneous spectroscopic [Fe/H] catalogue of Cayrel de Strobel et al. (1992) data from other sources and estimated systematic and accidental errors to some of those sources. Application of the data to further improvement of photometric calibration is discussed.
%K stars: abundances - techniques: photometric

%R 1994A&AS..108..447H
%J-448
%A Heck A., Egret D., Ochsenbein F.
%T StarWorlds - StarBits. (Announcement of two databases).
%F 1994.11.15
%B Two databases have been made available through the CDS WWW server: StarWorlds, a database of astronomy, space sciences and related organizations of the world, and StarBits, a database of abbreviations, acronyms, contractions and symbols in the same fields.
%K databases - astronomy - space sciences - related fields - organizations - abbreviations - acronyms  - contractions - symbols

%R 1994A&AS..108..449M
%J-454
%A Milone A., Barbuy B.
%T TiO bands as a function of stellar parameters.
%F 1994.11.15
%B TiO bands at {lambda}{lambda} 705-745, 615-630, 594-600 nm are clean strong features in metal-rich systems such as metal-rich globular clusters and normal galaxies. In the present work, we study the behaviour of TiO bands as a function of stellar parameters for individual stars trying to establish a calibration of TiO bands intensity vs stellar parameters. These features can be used together with more usual ones such as Mg_2_ to better derive metallicities.
%K late-type stars - stars: fundamental parameters

%R 1994A&AS..108..455S
%J-459
%A Salgado M., Bonazzola S., Gourgoulhon E., Haensel P.
%T High precision rotating neutron star models. II. Large sample of neutron star properties.
%F 1994.11.15
%B A new and highly precise numerical approach for computing stationary rotating stellar configurations in general relativity has been employed to construct rotating neutron star models. Fourteen equations of state (EOS) of cold dense matter have been used to produce a "catalog" of thousands neutron star models, parametrized by the EOS, the central energy density and the angular velocity. The results are presented in a series of tables for each EOS. A particular emphasis is
put on the properties of maximal mass models. These latter are useful to constrain the EOS, taking into account the observed pulsars.
%K relativity - stars: neutron; rotation; pulsars - equations of state