bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of the Moon: Recent Modification of Previous Ideas
Authors: Levin B. J.
Published: June 2019

New data on the Moon obtained from its study by space probes and analyses of returned lunar samples give new ‘boundary conditions’ for a study of its origin and evolution.
Re-discussion, from the Wiewpoint of Aerodynamics. Remarks on Steady Perfect Fluid Flow with Spherical Symmetry
Authors: Liepmann H. , Germain P.
Published: June 2019

As discussed by DEUTSCH, the following gas-dynamical problem arises in the study of a stellar atmosphere: find a steady outward flow, originating from a star, which is compatible with the interstellar medium. In what follows, spherical symmetry will be assumed; moreover, the gas will be considered as a perfect gas with constant specific heats.
Age and Metallicity Distributions among Galactic Disk Stars
Authors: Nissen P.E.
Published: June 2019

Observational studies of the relations between ages, metallicities and kinematics of disk stars in the solar neighbourhood are discussed with emphasis on the recent survey by Edvardsson et al. (1993), and galactic metallicity gradients inferred from these nearby stars are compared with gradients determined from distant B stars and open clusters.
Effects of Late Mergers
Authors: Schweizer Francois
Published: June 2019

Perhaps the single most important component missing from Baade's famous stellar-populations paper is the cold gas, in both its atomic and molecular forms. This review of the effects of late mergers concentrates on the role that this gas plays in forming new stellar populations and defining the characteristics of merger remnants and of some early-type galaxies.
Abundances of Heavy Elements in Halo Stars
Authors: Zhao G.
Published: June 2019

We reanalyzed the observational material of high resolution, high signal-to-noise spectra for a sample of 27 halo stars. The data were collected with the Coudé Echelle Spectrometer (CES) fed by the 1.4m Coudé Auxiliary Telescope (CAT) at the European Southern Observatory (La Silla, Chile). Data reduction are the same as described in a previous paper (Zhao and Magain, 1991). However, the non-linearity present in the data was corrected by using an empirical fitting formula (Gosset and Magain, 1993). The atmospheric parameters of these program stars have been determined. Effective temperatures were derived from b – y and V – K color indices by using the calibration of Magain. Surface gravities were determined by forcing the Fell lines to indicate the same abundance as the high excitation FeI lines. Metallicities were derived from Strömgren m1 indices. The abundances of a number of heavy elements, namely, strontium, yttrium, zirconium, barium, lanthanum, cerium and europium, are deduced on the basis of a new data reduction. The main results are: (1) The elements of the first peak, strontium–yttrium–zirconium, show the odd–even effect: strontium and zirconium are less deficient than yttrium in halo stars. (2) The yttrium abundance is constant for all stars with [Fe/H] > −2.5. (3) [Ba/Fe] values are 0.25 dex higher than solar for [Fe/H] > −1.8. (4) The barium overdeficiency increases with decreasing metallicity when [Fe/H] < – 1.8. (5) Lanthanum and cerium are overdeficient with respect to iron. (6) Europium is overabundant for −1.0 > [Fe/H] > −2.0.
The Scale Height of Blue Halo subdwarf B Stars
Authors: De Boer K.S. , Theissen A. , Heber U. , Moehler S.
Published: June 2019

Numerous blue halo stars have been discovered during the past decade (e.g. the Palomar-Green Survey). Many are horizontal branch type, being HBA, HBB, sdB, or sdO star. The sdB stars (Teff between ≈ 18 000 and ≈ 30 000 K) are the endproducts of evolution in the red-giant phase. This means that the spatial distribution of the sdB stars can be used to get insight in the population nature and in their spatial origin.
The Status of Absolute Proper Motions and the Kinematics of Globular Clusters
Authors: Geffert M. , Dauphole B. , Colin J. , Odenkirchen M. , Tucholke H.-J. , Ducourant C.
Published: June 2019

We have studied a sample of 26 globular clusters for which so far absolute proper motions exist in the literature. The proper motions were combined with distances and radial velocities for a determination of the space motion of the clusters. Using different galactic potentials (see Dauphole & Colin 1994 and references therein) we calculated the orbits of the globular clusters and their time averaged eccentricities, total energies, and apo- and perigalactic distances. The relation of the orbital quantities to the metallicities of the globular clusters has been studied. Preliminary results of this study were presented in Geffert et al. (1993).
Determination of earth rotation and station coordinates from Lageos data
Authors: Sinclair A. T. , Appleby G. M. , Xia J. Y.
Published: June 2019

A package of computer programs for the analysis of satellite laser ranging data has been written at the Royal Greenwich Observatory. The methods used are described, and the Earth rotation parameters and station coordinates derived from the MERIT Lageos data are given, with comparisons with other determinations. The uncertainty of the absolute value of the z-coordinate of the stations is discussed, and a method of short-arc analysis for determining baselines is described.
Nutations and inelasticity of the Earth
Authors: Dehant V.
Published: June 2019

The adopted nutation series correspond to an elliptical uniformly rotating Earth with an elastic inner core, a liquid core and an elastic mantle. There exist nowadays a difference between the theoretical results and this theory. In this paper, we introduce the mantle inelasticity in the equations in order to give an idea of its contribution to the nutations.
Analysis of recent polar motion data in view of excitation function and possible seismic causes
Authors: Lenhardt H. , Groten E.
Published: June 2019

Recent BIH-data from September 1979 - September 1986 have been deconvolved. The excitation function has been considered in detail and a spectral analysis indicates that there are atmospheric contributions; moreover, the September 19, 1985 Mexican Earthquake has been related to polar motion and a possible tidal triggering mechanism has been investigated.
X-Ray Novae and Related Systems
Authors: Wheeler J. Craig , Kim Soon-Wook , Mineshige Shin
Published: June 2019

Accretion disk thermal instability models have been successful in accounting for the basic observations of dwarf novae and the steady behavior of nova-like systems. Models for the dwarf-nova like variability of the old nova and intermediate polar GK Per give good agreement with the burst amplitude, profile and recurrence time in the optical and UV. A month-long “precursor plateau” in the UV is predicted for the expected 1992 outburst prior to the rise to maximum in the optical and UV. The models for the time scales of the outbursts and corresponding UV spectra at maximum are consistent with the inner edge of the accretion disk being essentially constant between quiescence and outburst and a factor of four larger than the corotation radius. These conclusions represent a challenge to the standard theory of magnetic accretion. Disk instability models have also given a good representation of the soft X-ray and optical outbursts of the X-ray novae A0620-00 and GS2000+25. Formation of coronae above the disk, heated by magneto-acoustic flux from the disk, may account for the temporal and spectral properties of the hard X-ray and gamma ray emission of related sources such as Cyg X-1, GS 2023+33 (V404 Cyg), 1E 1740.7-2942 (the “Galactic Center” Einstein Source), and GS 1124-683 (Nova Muscae).
Dynamics of the Galactic Bulge
Authors: Zeeuw Tim De
Published: June 2019

Recent work on the intrinsic shape, the internal kinematics of stars and gas, and the dynamics of the Galactic Bulge is discussed. Starcounts, measurements of the integrated light and the kinematics of the atomic and molecular gas all provide strong evidence that the Bulge is triaxial, and is rotating fairly rapidly. To date, there is little evidence for triaxiality in the stellar kinematics: the available stellar velocities are consistent with Kent's (1992) oblate model. This unsatisfactory situation is expected to improve rapidly.
TiO bands in composite systems
Authors: Milone A. , Barbuy B.
Published: June 2019

TiO bands at λ 620 nm are synthesized. The behaviour of these bands as a function of stellar parameters is studied. Application to composite spectra of one galactic bulge globular cluster and to bulges of elliptical galaxies is also carried out. TiO bands may be useful metallicity indicators.
PG3, A field in the Bulge of Our Galaxy: Description of a Galactic Model
Authors: Ng Y.K. , Bertelli G. , Chiosi C. , Bressan A. , Habing H. , Poole R.S. Le
Published: June 2019

Preliminary results are shown of our study on the metallicities and ages of the stellar populations present in different components along the line of sight to field #3 of the Palomar-Groningen Variable Star Survey (PG3) with synthetic Hertzsprung-Russell Diagrams (HRDs).
Synthetic photometric indices for Galactic globular clusters
Authors: Malagnini M.L. , Fracassini L.E. Pasinetti , Covino S. , Buzzoni A.
Published: June 2019

A grid of synthetic spectral energy distributions, representative of old stellar populations, has been used to derive colors in different photometric systems, and to compare the theoretical predictions with observational data for galactic globular clusters.
Simple models of galactic bulges
Authors: Evans N.W.
Published: June 2019

We present a simple axisymmetric model with an elementary distribution function capable of representing galactic bulges. The gravity field of the galaxy is based on the axisymmetric logarithmic potential, which has a flat rotation curve. Bulges are built as isothermal distributions of stars embedded within the potential.
Mixing in collisionfree systems
Authors: Ziegler Harald J. , Wiechen Heinz
Published: June 2019

Results of dynamical, numerical simulations of self-gravitating systems are used to show the existence of non-uniform mixing in phase-space.
Peanut shaped bars
Authors: Sellwood J. A.
Published: June 2019

Recent 3-D N-body simulations have shown that the bars formed through the well-known global instability of discs later acquire a pronounced peanut shape when seen from the side. This paper reports a new calculation of the phenomenon using a finer grid and a slightly different initial model. The final peanut shaped bar, when viewed from within the disc, has an appearance remarkably similar to that of the Milky Way bulge. When viewed as a distant edge-on galaxy, an observer would see cylindrical rotation in the “bulge”.
Primeval starburst and bulge formation
Authors: Wada Keiichi , Habe Asao
Published: June 2019

Starburst phenomena in galaxies should have been common in the epoch of galaxy formation. How did the primeval starbursts affect the structure or the properties of the host galaxies?
On the difference in formation history between bulges and ellipticals
Authors: Rocca–Volmerange B. , Sil'chenko O. K.
Published: June 2019

On the diagram (Fe5270, Mg5175) ellipticals and bulges of disk galaxies (from S0 to Sc) maintain a very different position: E's seem to be overabundant in Mg, bulges seem to have a solar ratio Mg/Fe, except several ones who are overabundant in Fe.
The velocity fields of elliptical galaxies: constraints on intrinsic shapes
Authors: Statler T. S. , Fry A. M.
Published: June 2019

The problem of determining the intrinsic shapes of elliptical galaxies cannot be solved using photometry alone. Measuring rotation on the apparent major and minor axes adds a kinematic constraint, but does not significantly improve the situation. We find that having two more spectra, at the ±45° position angles, gives enough kinematic information that much tighter limits can be placed on the intrinsic axis ratios than are possible otherwise.
High-n Hydrogen Lines in Solar Infrared Spectra from Balloon-borne, Mauna Kea, and ATMOS Observations
Authors: Boreiko R. T. , Clark T. A. , Naylor D. A. , Busler J. R.
Published: June 2019

This paper reports the observation of high-n lines in emission from n = 12-11, 13-12, 14-13 and 16-15 Rydberg transitions in H, Mg and Si in solar far IR spectra taken from balloon altitudes, in which the H I line intensities are found to exceed those from the heavier elements. Tentative identification is also made of the n = 8-7 hydrogen line in emission on 20 μm spectra taken from Mauna Kea. The characteristics of the hydrogen lines are compared with lower-n transitions seen in the Space Shuttle ATMOS spectra, in which Brackett, Pfund and n = 6 lines with Δn = 1, 2, 3 and 4 are seen as broad absorption features, while the n = 7-6 line shows a small emission peak within a broader absorption line and the n = 9-7, and possibly the 11-8, transitions appear as weak emission lines. These results indicate that the transformation from absorption to emission occurs at longer wavelengths for hydrogen lines than for those of heavier elements.
Infrared Measurements of Stellar Magnetic Fields
Authors: Saar Steven H.
Published: June 2019

I review the advantages, techniques, and results of measurement of magnetic fields on cool stars in the infrared (IR). These measurements have generated several important results, including the following: the first data on the magnetic parameters of dMe and RS CVn variables; evidence for field strength confinement by photospheric gas pressure; support for the correlation between magnetic flux and rotation, with possible saturation at high rotation rates; indications of horizontal and/or vertical magnetic field structure; and evidence of spatial variations in B over a stellar surface. I discuss these results in detail, and suggest future directions for IR magnetic field research.
Solar Optical Interferometry
Authors: Ridgway Stephen T.
Published: June 2019

Optical interferometry has numerous applications in stellar and extragalactic astronomy. It also offers the potential for unique solar observations. This review describes current and planned activity in these areas and some possibilities for the future.
The IR Emission Features and Hydrogenated Amorphous Carbon (HAC) Particles
Authors: Duley W. W.
Published: June 2019

Various sources of non-equilibrium radiation from interstellar dust are discussed. It is shown that the existence of cirrus emission at 12 and 25 μm is consistent with the presence of amorphous carbon dust and arises from thermal spikes within ≃ 10å subvolumes of normal (0.01-0.1 μm radius) dust grains. The 3.28 μm unidentified infrared (UIR) feature also arises in this way, as the radiative relaxation of high energy vibrational modes accompanying a thermal spike in hydrogenated amorphous carbon. Extended red emission (ERE) and near-infrared (NIR) emission are also discussed and are postulated to originate as edge and defect luminescence from HAC solids with bandgaps Eg ≲ 2.5eV.
Fractal Dust Grains
Authors: Wright Edward L.
Published: June 2019

Dust particles in the interstellar medium are almost certainly not spherical or any other shape which allows an analytical calculation of the extinction curve, even in the Rayleign limit. Particles in soot and interplanetary dust particles are aggregates formed by subclusters which stick together. This paper uses the discrete dipole approximation (DDA) to compute the absorption and extinction curves for fractal shapes generated by this clustering process. For fractals made from graphite the UV extinction curve shows a bump near the observed 220 nm feature, and a far infrared emission efficiency many times greater than that for spheres.
Comet Dust: Connections with Interstellar Dust
Authors: Knacke R. F.
Published: June 2019

The Comet Halley campaigns resulted in an enormously better understanding of the composition of comets. Silicates, organic compounds, and volatile ices comprised ofH2O, CO, CO2,S2,CN, and possiblyCH4andOCSoccur in comet grains. These are all known or suspected constituents of interstellar dust. We review the chemical, elemental, and isotopic compositions of comet dust and compare this with interstellar matter. The many intriguing parallels suggest, but do not yet establish, a direct connection between comet dust and interstellar dust.
Infrared Emission from Dust in Supernovae and Supernova Remnants
Authors: Dwek Eli
Published: June 2019

The need to replenish the reservoir of interstellar dust grains that are continuously being destroyed in the interstellar medium, and the presence of isotopic anomalies in meteorites, suggest that supernovae may be important sources of interstellar dust. Infrared observations of supernovae or their unmixed ejecta may provide the first direct evidence for newly-formed grains in this environment. The recently discovered supernova, SN 1987A, currently offers the best prospects for observing the actual process of dust formation in a supernova.

In contrast, supernova remnants constitute the most important grain destruction mechanism in the galaxy. Interstellar dust swept up by the expanding blast wave is predominantly heated and destroyed by collisions with a shocked x-ray emitting plasma. Infrared observations of remnants can therefore provide valuable information on the interaction between dust particles and a hot gas. This interaction can best be studied in supernova remnants detected with the Infrared Astronomical Satellite (IRAS). This paper reviews what we have learned so far on the subjects of grain formation and destruction by studying the infrared emission from supernovae and supernova remnants.
Second Epoch of Simultaneous λ3.6 and λ13 cm Observations of the Pair of Quasars 1038+528 A,B
Authors: Marcaide J. M. , Bartel N. , Bonometti R. J. , Corey B. E. , Cotton W. D. , Gorenstein M. V. , Preston R. A. , Ratner M. I. , Rogers A.E.E. , Shapiro I. I.
Published: June 2019

On 1983 May 10–11 we undertook simultaneous λ3.6 and λ13 cm Mark III VLBI observations of the quasars 1038+528 A,B. Our experimental conditions (i.e., synthesized band, uv-coverage, etc.) were almost identical to those we used on 1981 March 17–18. Thus, we could make a direct comparison of the results from both epochs.
Small Steep-Spectrum Sources: Jets Colliding with Ambient Gas
Authors: van Breugel Wil , Ren-dong Nan , Schilizzi R. T. , Fanti C. , Fanti R.
Published: June 2019

A large fraction of sources in flux limited radio samples consists of compact steep spectrum (CSS) sources (Fanti et al. 1987). These objects have their dominant emission on kiloparsec scales and are found in a variety of active galaxies, including Seyfert II's, peculiar galaxies and quasars. Observations of very nearby CSS sources have shown good correlations between their complex radio structures and optical emission-line gas suggesting violent interactions between jets and dense gas in their ambient interstellar media (van Breugel et al. 1984). Similar jet/gas interactions may occur in more distant and more powerful CSS sources.
327 MHz Observations of 3C 84, 3C 120 and 1148-001
Authors: Kulkarni V. K. , Ananthakrishnan S.
Published: June 2019

We have made VLBI observations of a mixed sample of bright galaxies and quasars at 327 MHz using the Ooty Radio Telescope in India and the telescopes at Jodrell Bank, Westerbork, Torun, and Crimea in December 1983 and March 1986. MK II recording was used and the data were processed at MPI, Bonn. The preliminary results of the 1983 analysis (Ananthakrishnan and Kulkarni 1986) showed most of the nearby galaxies to be resolved over the longest baselines of 8 million wavelengths. The only seyfert galaxies for which good S/N ratio was available at the longest baselines were 3C84 and 3C120. Although UV coverage was poor we attempted to make maps of these objects. The radio source 1148-001 was used for gain calibration of the telescopes.
High Dynamic Range Mapping of a Complex Radio Source – M87
Authors: Muxlow T.W.B. , Junor W. , Spencer R.E. , Simon R. , Benson J. , Reid M.
Published: June 2019

The well known jet in M87 (Virgo A) has been extensively studied in the radio regime using conventional arrays with resultant resolutions in the range 0.22–1 arcsecond. We present here the results of a VLBI experiment to map the jet over its entire length (30 arcseconds) to high resolution. The observations were made in April 1984 at 1.67 GHz with a ‘World Array’ containing 18 VLBI telescopes. In addition, simultaneous observations were performed with the 6 station MERLIN array.
Theory of Astronomical Masers
Authors: Kylafis Nikolaos D.
Published: June 2019

The theory of astronomical masers is reviewed. As with laboratory masers, masing occurs when a transition between two energy levels of a molecule exhibits inverted populations. In order to present the basic concepts about masers, an idealized two-level system is used. The exact energy level structure is taken into account later on when the pumping of specific molecules is discussed. Unlike laboratory masers, where the radiation must be bounced between two mirrors to accumulate gain, the propagation of radiation in astronomical masers is a lot simpler. This is because astronomical masers are single-pass and broadband. Thus, the main theoretical effort has concentrated on inventing efficient mechanisms that produce population inversion. Specific pumping mechanisms for the three molecules (H2O, SiO, and OH) that exhibit strong masing are presented and their ability to explain the observations is discussed.
The Super Luminous Maser Source in the Nucleus of NGC 3079
Authors: Haschick Aubrey D. , Baan Willem A. , Schneps Matthew H. , Reid Mark J. , Moran James M.
Published: June 2019

On 1984 October 6 we conducted a 3-station intercontinental Mark II VLBI experiment in order to study the very luminous water vapor maser source in the nucleus of the galaxy NGC 3079, which was detected first by Haschick and Baan (1985) using the Haystack Observatory 36.6 m antenna. The cross correlation spectrum for the longest Owens Valley to MPI baseline is presented in Figure 1 and shows the phase variation across the width of the brightest feature at 955.7 km s−1 to be less than 10 degrees of phase.
Extreme Scattering Events
Authors: Fiedler Ralph , Dennison Brian , Johnston Kenneth
Published: June 2019

Dally flux density measurements of 36 extragalactic radio sources over a seven year period, obtained by the Green Bank interferometer, reveal several unusual minima in the light curves that do not follow typical source variations (Fiedler et al. 1987). The most significant departure from typical source variability occurred at both frequencies in the quasar 0954+658 between 1980.95 and 1981.3. Refractive focussing by small scale inhomogeneities in an ionized structure in the interstellar medium appears to be the most likely explanation.
Interstellar Scattering Towards Cyg X-3
Authors: Wilkinson P. N. , Spencer R. E. , Nelson R. F.
Published: June 2019

MERLIN observations at 0.408 GHz of the December 1985 outburst of Cyg X-3 have enabled us to characterise the angular broadening, caused by interstellar scattering, very accurately. The scattering along the line of sight towards Cyg X-3 is exceeded by only two other lines of sight through the Galaxy: towards the Galactic centre (see e.g. Lo et al. 1985. Nature, 315, 124) and towards NGC 6334 (Rodriguez et al. 1982. Astrophys. J., 225, 103); as a result quite short baselines are needed to study the scattering disk at 73 cm wavelength (0.408 GHz). The projected MERLIN baselines for our observations cover the range from a few km (on which the source was unresolved and had a correlated flux density ∼3.6 Jy) to ∼130 km (on which the source was totally resolved i.e. a correlated flux density <0.030 Jy). The basic result from these observations is that over this range of baselines the scattering appears to be purely diffractive in character. The scattering disk is, to quite a good approximation, a circular gaussian and shows no evidence of fine scale substructure. Model fitting to the visibility amplitudes, assuming circular symmetry, yields θ0.408GHz = 2.85±0.05 arcsec (FWHM).
Towards the Definition of a Unified Celestial Optical/Radio Reference Frame
Authors: Johnston K. J. , Russell J. , de Vegt Ch. , Hughes J. , Jauncey D. , Nicholson G.
Published: June 2019

An almost inertial celestial reference frame based upon extragalactic sources is in the process of being established. This reference frame is to be global with a minimum density of one source/100 square degrees. The source positions will be based upon radio observations and will allow optical reference frames to be related to this frame at the 0.03 arc second level.
Meridian & Astrolabe Observations of Radio Stars: A Contribution to the Connection of Radio and Optical Reference Systems
Authors: Sarasso M. , Chiumiento G. , Poma A.
Published: June 2019

Optical positions of eight radio stars observed with the Photoelectric Transit Instrument (PTI) at Torino and with the Danjon Astrolabe (AST) at Cagliari are presented here. The values of observed right ascensions have been computed at the Epoch J2000.0.
Astrometry in Local Reference Frames for Deep Space Navigation
Authors: Treuhaft R. N.
Published: June 2019

Future deep space missions will benefit from submilliarcsecond angular navigation accuracy (< 25 km projected distance at Neptune). Conventional Very Long Baseline Interferometry (VLBI) measurement strategies entail observations of a radio source (RS) and spacecraft pair. To increase the 3–5 milliarcsecond accuracies currently attainable, instrumental improvements could be coupled with either of two methods: 1) Use improved calibration measurements with the single RS as the spacecraft reference, or 2) use a reference frame established by a local network of RS's near the spacecraft to reduce the contribution of sky-dependent error sources. The demanding baseline vector (earth orientation) and tropospheric calibrations needed to realize submilliarcsecond accuracy with the single-source strategy would not be necessary with the multi-source strategy. The two strategies are compared via a sample covariance analysis. In this analysis, the single-source method yields 1.5 milliarcseconds for the navigation accuracy, while the multi-source method yields 0.5 milliarcseconds.
Constraints on North American-Pacific Plate Boundary Deformation in Central California from VLBI and Ground-Based Geodetic Data
Authors: Sauber Jeanne , Jordan Thomas H. , Beroza Gregory C. , Clark Thomas A. , Lisowski Michael
Published: June 2019

To accommodate the relative motion across the North American-Pacific plate boundary predicted by global plate solutions, significant deformation on faults other than the San Andreas is necessary. In central California, this deformation is thought to include distributed compression perpendicular to the San Andreas as well as right-lateral strike-slip motion parallel to the San Andreas on faults such as the San Gregorio/Hosgri system. A self-consistent set of VLBI observations from experiments beginning in October 1982 is used to determine the vector rate of change of station position at central California VLBI sites Ovro, Mojave, Vandenberg, Fort Ord, Presidio, and Point Reyes. To estimate VLBI station positions, a procedure is used that minimizes the uncertainties in defining a reference frame by including a priori geologic and geodetic information. The vector rate of change of station positions provides constraints on the integrated deformation rates between stations. Geologic and geophysical data suggest that the rate and mode of deformation varies on both local and regional scales. Thus, the VLBI derived results are interpreted in the context of an overall tectonic framework by examining geologic and ground-based geodetic data.
Improved Analytic Nutation Model
Authors: Yoder C. F. , Ivins E. R.
Published: June 2019

Models describing earth's nutations can be separated into two major components, plus several small perturbations, of which ocean tides and solid friction are the most significant. The primary element of a successful model is an accurate rigid earth nutation theory. The effect of mantle elasticity and differential nutation of the fluid core is then obtained as a correction factor which multiplies the rigid body result. Wahr's (1981) theory is certainly the most sophisticated elastodynamic response model. However, we have found that the simple model of Sasao et al., (1980) differs from Wahr's theory term by term by less than 0.3mas if a modern earth structure model (1066B) is used to evaluate the nutation structure constants.
The Low frequency Space Array (LFSA)
Authors: Weiler K. W. , Dennison B. K. , Johnston K. J. , Simon R. S. , Spencer J. H. , Erickson W. C. , Kaiser M. L. , Cane H. V. , Descn M. D. , Hammarstrom L. M.
Published: June 2019

At the lowest radio frequencies (≤30 MHz), the Earth's ionosphere transmits poorly or not at all. This relatively unexplored region of the electromagnetic spectrum is thus an area where high resolution, high sensitivity observations can open a new window for astronomical investigations. Also, extending observations down to very low frequencies brings astronomy to a fundamental physical limit where the Milky Way becomes optically thick over relatively short path lengths due to diffuse free-free absorption.
Anisotropy of the Microwave Background and Biased Galaxy Formation
Authors: Kaiser Nick
Published: June 2019

Fluctuations in the microwave background will have been imprinted atz≃ 1000, when the photons and the plasma decoupled. On angular scales greater than a few degrees these fluctuations provide a clear view of any primordial density perturbations, and therefore a clean test of theories which invoke such fluctuations from which to form the structure we see in the universe. On smaller angular scales the predictions are less certain: reionization of the gas may modify the spectrum of the primordial fluctuations, and secondary fluctuations may be generated.

Here I shall review some recent theoretical developments. A brief survey is made of the currently popular theories for the primordial perturbations, with emphasis on the predictions for large scale anisotropy. One major uncetainty in the predictions arises from the normalisation of the fluctuations to e.g. galaxy clustering, and much attention is given to the question of ‘biased’ galaxy formation. The effect of reionization on the primordial fluctuations is discussed, as is the anisotropy generated from scattering off hot gas in clusters, groups and galaxies.
Results of the Pisces-Perseus HI Redshift Survey
Authors: Giovanelli Riccardo , Haynes Martha P.
Published: June 2019

We report on the current status of the HI redshift survey in the Pisces-Perseus supercluster and present results based on a sample of approximately 4700 redshifts known in the 6h by 45° region of the sky dominated by the supercluster. In particular we derive density contrasts between voids and high density regions and discuss the existence of a luminosity bias between galaxies that reside in regions of different local density. Such a bias is not the consequence of the well-known pattern of morphological type segregation, but results from a difference in the shape of the luminosity function of galaxies in high and low density regions. Bright galaxies tend to be relatively less abundant, and faint ones relatively more so, in low density environments.
Quasar Clustering and the Evolution of Structure
Authors: Shaver P. A.
Published: June 2019

Quasar clustering has now been confirmed at a high level of significance, and there is evidence for its evolution. A review is given of these developments, and of other evidence related to the evolution of structure.
Acquisition of angular momentum in the proto-galactic phases
Authors: Caimmi R. , Andriani E. , Secco L.
Published: June 2019

Following Peebles (Ap.J. 155, 393; Astron.Astrophys. 11, 377)and Efstathiou and Silk (Fund.Cosm.Phys. 9, 1) we assume that a developing proto-galaxy of mass M=1011M⊙ gains angular momentum during a first Phase 1 exten ding from recombination to the maximum expansion and then a second Phase 2 from the maximum expansion to a relaxed virialized structure passing through an intermediate Phase I.A very simple model is proposed in which a first mechanism connected with increasing density perturbatio ons leading to a torque ∼ t2/3, is applied to a spherical homogeneus structure. The initial conditions for its dynamical evolution are taken from a cosmological flat model (Ω = 1) with an isothermal perturbation mass spectrum. Phase 2 begins when the proto-galaxy is completely separated from the background and until this Phase it has been recognized that the initial spherical symmetry turns out to be well preserved, provided the angular momentum gained does not exceed 3.6 1073 g cm2 sec−1.
Large Scale Streaming in the Wake of a Loop of Cosmic String
Authors: Zurek W. H. , Hoffman Y.
Published: June 2019

Large-scale streaming can be caused by a single “strange attractor” located at a distance D ∼ 45h−1 Mpc from our galaxy (Faber, these proceedings). These observations can be interpreted in terms of a wake of a large loop of cosmic string laid down at z ≤ 1000. The velocity field induced by a stationary loop modeled as a thin spherical shell has a radial dependence v ∼ r−1, consistent with the observed. Zeldovich spectrum of density perturbations would result in v ∼ r−3. The stationary loop model can account for the observed amplitude of the peculiar velocity (v ≃ 500km/s at D ≃ 45h−1 Mpc) only if the dimensionless string tension Gμ/c2 is large, ≳ 7 × 10−6. When peculiar velocities of the loops are taken into account, the estimate of μ can be lowered: The loop is now able to spread its influence. The flow induced by the loop with the physical radius Rs = 36h−1 kpc moving initially with vs = 0.1c and laid down at z=500 is shown in the top portion of the diagram below. The distances are in h−1 Mpc's. The initial comoving loop size and location are indicated by a circle and the present-day location by a dot. Bottom part of the figure shows the line-of-sight peculiar velocities with respect to the microwave background seen by the observer located at the point marked with the square. The loop induces v = 480km/s at ∼ 35h−1 Mpc from the nonlinear part of the diagram - presumed location of the “strange attractor” - providing that its mass is Ms = 9 × μRs, with Gμ/c2 = 5 × 10−6. A loop with Rs ≃ 300h−1 kpc deposited later, at z = 125, would result in v = 520km/s on a scale of 45h−1 Mpc.
Gravitational Lensing: Cosmological Implications
Authors: Nottale Laurent
Published: June 2019

In the present poster, we first address theoretically the problem of gravitational amplification by extended density fluctuations and then compare statistically our new predictions to actual samples of galaxies and QSOs.
The “Carte Du Ciel” Instrument Of San Fernando: A Century Of Activity
Authors: Orte A.
Published: June 2019

The installation of the “Carte du Ciel” instrument was of great transcendency for the history of the Instituto y Observatorio de Marina. After briefly outlining the main difficulties for the development of the Observatory by that time, the personality of Captain Pujazón, responsible of the improvement of his institute and organizer of the work of the astrograph at San Fernando, is commented. We describe the spanish participation in the “Carte du Ciel” campaign and the subsequent use of the instrument in different international programs until the present days. The profitableness of the astrograph in continuing to support some aspects of the modern astrometrical research, is concluded.
Preserving The Past: Archival Preservation Of Observatory Publications Via An Optical Disk Project
Authors: Corbin Brenda G.
Published: June 2019

Important research in astronomy and many star catalogues have been published in observatory publications during the last century and a half. Many of these older volumes are now in poor condition and conservation experts estimate they will not survive another 100 years if action is not taken. This paper describes a proposed project to preserve these volumes using optical disk technology.
The Tycho Survey Of Stars Brighter than Eleventh
Authors: Egret Daniel , Høg Erik
Published: June 2019

The real-time attitude of the HIPPARCOS satellite (see Turon, this symposium) is monitored by a star mapper viewing a 40 arcmin. Wide band of the sky, ahead of the main field of view, through a system of four vertical and four inclined slits (fig. 1). The resulting on-board precision will be 1 arcsec. rms and on-ground attitude reconstitution will later improve this value to 0.1 arcsec. rms.

The TYCHO project (approved by ESA in 1981) consisted in introducing dichroic beam splitters and a pair of redundant photomultipliers (with a bandpass close to Johnson B and V) into the science payload. This configuration will give a complete survey of the sky down to 11th magnitude in B, during the two and a half years of the mission. The data reduction is prepared by a scientific consortium (TDAC) which will be described in more details in section 4. The work related to the TYCHO Input Catalogue is described in section 2. An overview of the data reduction process is given as section 3, and aspects of the TYCHO outputs are discussed in section 5.
The Lick Northern Proper Motion Program
Authors: Hanson Robert B.
Published: June 2019

This paper reviews the Lick Northern Proper Motion (NPM) program, describing its goals, organization, and methods, summarizing its progress, and outlining the work remaining for the future. The first phase of the NPM program (outside the Milky Way) is now nearing completion. A detailed description of the NPM program has been given by Klemola, Jones, and Hanson (1987). Recent results using the NPM data in a study of solar motion and galactic rotation are presented in a separate paper in this Symposium.
The Second Palomar Sky Survey
Authors: Reid Neill
Published: June 2019

The Carte du Ciel was the first photographic survey of the entire sky, extending to 15th magnitude in the blue “photographic” passband. The first Palomar sky survey followed in this tradition, covering the sky north of δ = −30° to a limiting magnitude of ≃ 20 in both blue and visual/red wavelength ranges, while the Whiteoak extension added the fields to declination −42° in the latter color. In the thirty years that have elapsed since the completion of the original survey there have been substantial improvements in emulsions and sesitization techniques, as well as an increase in the wavelength range accessible to photography. These techniques have been ably exploited by the UK Schmidt telescope, and a cursory comparison between any UKST IIIaJ plate and an original POSS 103a-O photograph highlights the considerably improved depth and resolution of the southern survey. We have, therefore, embarked on a second Palomar survey, POSS 2, in an effort to redress the balance. This paper outlines the progress made to date and go on to describe some of the scientific programs that are planned.
The Infrared Astronomical Satellite Survey Of The Sky
Authors: Chester T.
Published: June 2019

The Infrared Astronomical Satellite (IRAS) surveyed 98% of the sky during 1983 at the wavelengths of 12, 25, 60, and 100 μm. The survey was enormously successful, producing catalogs containing more than 300,000 sources as well as digital images of the entire covered sky. The IRAS survey has revolutionized several fields of astronomy and impacted nearly every field. This paper discusses the general characteristics of the IRAS survey and lists the major results obtained so far.
Presentation Technique De L'Astrolabe Photoelectrique Du Cerga
Authors: Billaud G. , Boche R. , Furia M. , Vigouroux G.
Published: June 2019

The prototype of the photoelectric astrolabe, conceived at CERGA with the assistance of the observatories of Paris and Nice, is intended for the improvement of star catalogues. In addition to the technical aspects, we present here some results that indicate the quality of data obtained.
Quasars in the Field of SA94 - A Colour Survey
Authors: Cristiani S. , Barbieri C. , Iovino A. , Franca F.La , Nota A.
Published: June 2019

In Barbieri and Cristiani (1986) the results of a preliminary objective prism survey in the SA94 were reported, in Barbieri et al. (1987) these results were compared with the colour survey of Mitchell et al. (1984). The study continued with the creation of a sample of UVX candidates in the 10 central square degrees of the field.
Multicolor CCD Photometry of a Homogeneous Sample of Seyfert 1 Galaxies
Authors: Bonoli C. , Bonoli F. , Danese L. , Delpino F. , De Zotti G. , Granato G. , Zitelli V.
Published: June 2019

We have observed a homogeneous sample of Seyfert 1 and 1.5 galaxies with the aim to determine the luminosity function of Seyfert nuclei. Observations were made with the CCD cameras of Asiago and Loiano Observatories in B, V and R bands in order to isolate the contribution of different stellar populations. A photometric decomposition into three components (disc, bulge and nucleus) was fitted to the observed luminosity profiles to separate the nuclear and the host galaxy contributions and to understand whether underlying galaxies actually behave as “normal” galaxies.
A Search for Companions to High Redshift (z ≥ 3.0) Quasars
Authors: Kjærgaard Per , Møller Palle , Jensen Marianne , Jørgensen Inger
Published: June 2019

Following the discovery by Djorgovski et al. (1985) of a companion to the high redshift quasar PKS 1614+051, we initiated a systematic search for such objects with the Danish 1.5 meter telescope at La Silla. The observing technique is CCD exposures in narrow filters (FWHM=100Å) centered on the redshifted Lyα. For an exposure time of 40 min. Our limiting magnitude is around 22.0 (where the r.m.s. error is approximately ±0.15), according to test runs with DAOPHOT. The aim of the search is to clarify the nature of such companions: are they “primordial” galaxies? Lyα clouds associated with the quasar? - and how frequent is such a phenomenon? Up to now we have covered 26 fields around quasars with redshift ≥3.0 (which is about 25% of all high redshift quasars in the Veron and Veron Catalogue). Furthermore 12 fields around z≈2.5 has also been observed (see Table 1). A quick visual inspection of all our frames has not revealed any companions except for the object found by Djorgovski et al. (which is easily picked up by our technique). However, a thorough photometric reduction (using DAOPHOT) might reveal fainter candidates. Taken together with the fields reported observed by Hu and Cowie (1987) and Djorgovski et al. (1987), a total of about 50 fields have so far been observed. The preliminary conclusion is therefore that such companions, whatever they might be, are very rare, and certainly much rarer than similar systems found around quasars of low redshift.
Short Time Scale Variability of Active Galactic Nuclei: Einstein IPC Observations of PKS 2155-304 - A Report of Rapid Variations of Instrumental Origin
Authors: Beall J. H. , Snyder W. A. , Wood K. S.
Published: June 2019

The Einstein IPC observed the bright (5 mCrab) X-ray emitting BL Lac Object PKS 2155-304 on 1979 November 4th and 5th through 7th and on 1980 May 16th through 18th. A total of 17.4 hours were spent monitoring the source. Changes in intensity of between 10–50% are evident in the data for time scales of days and months. The source was constant to within 10% of the mean intensity on hourly time scales for all intervals of data except one. Repeated factor of 2 variations in intensity, occuring on 10–30 second time scales, were observed during the first 50 minutes of the 1979 Nov. 5th observation. These variations, however, were anticorrelated with variations seen in an adjacent background region. Concurrent MPC observations also failed to confirm the rapid changes, although they should have been readily detected. Thus, we conclude that the observed rapid variations are not intrinsic to the source, but originated in the IPC. These results can have implications for other IPC reports of short time scale variability for active galaxies and for source models based on such observations.
Rapid Infrared and Optical Variability in 3C 273
Authors: Robson E. I. , Courvoisier T.J.-L. , Bouchet P.
Published: June 2019

The quasar 3C273 varied by up to 100% on timescales as short as one day in the optical and IR domains during February and March 1988. In February the source changed from a behavior characterised by a stable IR flux and slow optical variations to one of recurrent optical and IR flares. Five optical flares, of amplitude up to 30–40% were observed, along with two IR flares, both of which were simultaneous with optical events. The second IR flare on March 9th rose from 46mJy to 66mJy (twice the normal (quiescent) value) in one day. The data and some of their implications are described in Courvoisier et al. (1988).
QSO Emission Line Redshift Differences
Authors: Junkkarinen Vesa
Published: June 2019

Redshift differences between QSO emission lines reflect the kinematical differences between the regions where the lines are produced. Gaskell (1982) discovered a systematic redshift difference between the broad lines of high ionization and the narrow forbidden lines that amounted to a blueshifting of C IV λ1549 by 600 km s−1. Gaskell obtained this result basically by comparing C IV emission and Mg II λ2798 emission in one sample of QSOs and by comparing Mg II emission and the narrow forbidden lines in a different sample. So the distribution of C IV emission redshifts relative to the narrow forbidden lines was not sampled directly by Gaskell. By observing QSOs with redshifts near 1.3, it is possible to directly sample the redshift difference between C IV and the narrow forbidden lines. This redshift difference and its distribution should provide kinematical information on the clouds of gas that give rise to the broad lines of high ionization. The narrow forbidden lines are the preferred velocity reference because they may reflect the systemic velocity of the QSO.
Soft X-ray Spectra of Seyfert Galaxies
Authors: Urry C. M. , Kruper J. S. , Canizares C. R.
Published: June 2019

The first X-ray (2–10 keV) spectral surveys of active galactic nuclei (AGN) were remarkably uniform, with spectral indices narrowly distributed about α=0.65, independent of radio-emitting properties or X-ray luminosity (Mushotzky 1984). In the few AGN detected above 20 keV, this canonical power law extended to at least 50 keV (Rothschild et al. 1983, Pounds 1985, Worrall et al. 1980; Halpern 1982; Worrall and Marshall 1984). In practice these surveys were dominated by low luminosity Seyfert 1 galaxies.
The Infrared and X-ray Continua of Quasars: Is there a Connection?
Authors: Elvis Martin , McDowell Jonathan , Wilkes Belinda J.
Published: June 2019

The first Einstein IPC X-ray spectra of quasars had slopes similar to their infrared spectra (Elvis et al. 1986) suggesting that the infrared and x-ray continua of quasars might be two ends of a single power-law extending over at least 4 decades of the electromagnetic spectrum. In retrospect this was a bold claim based as it was on only eight quasars with limited infrared coverage. If true though it would greatly simplify the structure of the quasar continuum.
Composite Spectra of Some Active Galactic Nuclei
Authors: Tsuruta Sachiko
Published: June 2019

Recent years have seen some progress in the studies of the central engine of active galactic nuclei (AGN). On the observational side, past space missions such as HEAO-A, Einstein and EXOSAT have brought some considerable progress in the observations of X-ray spectra and time variabilities of AGN. More significant progress is expected in the immediate future due to the current and future space missions such as IUE, GINGA, the Hubble Space Telescope, ASTRO-D, ROSAT, and AXAF. Therefore, it would be important to continue parallel theoretical studies. In this report composite models are presented which naturally explain the observed continuum radiation from seyferts and radio-quiet quasars. Our aim is to explore the central engine of AGN. This class of AGN is selected because it is generally considered to give the most direct information on the central power-house.