bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinematics of Galactic Globular Clusters from Schmidt-Plate Astrometry
Authors: Scholz R.-D. , Hirte S. , Irwin M.J. , Odenkirchen M.
Published: June 2019

From measurements of Tautenburg Schmidt plates with the APM facility in Cambridge we obtained absolute proper motions of the Galactic globular clusters M 3 and M 92 directly with respect to large numbers of background galaxies (Scholz et al. 1993, 1994). We have extended our work to the dSphs in Draco and Ursa Minor (Scholz & Irwin 1994) and to other Galactic globular clusters using Tautenburg, Palomar and UK Schmidt plates. Combining our absolute proper motion of a cluster with its known radial velocity and distance (using common parameters of the solar motion) we derive the cluster orbit in the Galaxy (cf. Odenkirchen & Brosche 1992).
Strömgren Photometry of Stars in Baade's Window
Authors: Ruelas-Mayorga Alex , García-Ruíz Gabriel
Published: June 2019

Baade's Window (BW) has long been observed because of its low absorption and its position near the galactic centre. These characteristics permit the observation of many stars which are presumably members of the galactic bulge; although it is not possible to exclude contamination of this field by stars belonging to the galactic disc. Geometric arguments as well as galactic models allow to see that most of the stars are located far away from the solar neighbourhood. Based on this fact alone, many astronomers have assumed that the entire stellar population observed in BW consists of bulge stars.
Metal Abundances of Damped Lyα Systems and the Chemical Evolution of Spiral Galaxies
Authors: Fritze-V. Alvensleben Uta , Fricke Klaus J.
Published: June 2019

Our chemical evolution models describe in detail the enrichment process of a number of individual elements from 12C to 56Fe, including delayed SNI contributions. Variation of the characteristic timescale of star formation (SF) t∗ not only results in differences in the abundance evolution but also changes abundance ratios of elements originating from different nucleosynthetic sites, as e.g. [C/O], [O/Fe], or [Mg/Fe].
UV Central Spikes in Early Type Galaxies
Authors: Bertola F. , Cappellari M. , Burstein D. , Greggio L. , Renzini A. , Alighieri S. Di Serego
Published: June 2019

HST images of the E galaxies NGC 1399 and NGC 4552 and of the Sa NGC 2681 were obtained with FOC f/96 through the filters F175W, F220W, F275W and F342W. The most important discovery of these observations is the clear detection of central spikes in NGC 2681 and NGC 4552, that are prominent in each of the FOC images. No spike is detected in NGC 1399. The spikes appear unresolved by the 0″.07 core of the Pre-COSTAR PSF, corresponding to a physical size <~2-3 pc. We estimate V = 16.4 for the spike in NGC 2681 and V = 18.4 for that in NGC 4552, or ~ 107L⊙ in both cases. The spikes contribute less than a few percent of the UV flux sampled by IUE. We can offer three options for their nature: a central burst of star formation; effects of stellar interaction in a very dense environment; and a low level AGN. The first two options are currently entertained for the origin of the very dense star cluster at the center of our own Galaxy, whose size and luminosity are comparable to the corresponding limits for the two UV spikes (Genzel et al. 1994). A much fainter central spike (~ 105L⊙) is also seen at the center of NGC 205, and appears to be consistent with a modest burst of star formation (Bertola et al. 1995).
Enhanced Star Formation rates in Binary Interacting Elliptical Galaxies
Authors: Chatterjee Tapan K
Published: June 2019

We study the stellar orbits, as a function of the binary motion of two identical ellipticals, under initial conditions marginally sufficient for strong interaction. The stars were initially given circularly symmetric velocities. The tidal effects cause a redistribution of stellar orbits, resulting in crowding of stars in shells; the same attaining its maximum intensity slightly after a pericentric passage. As the galaxies recede, the structure disperses gradually by expanding; but is restored, intensified and forms at a shorter radial distance as the galaxies return for a subsequent approach in a shrinking orbit. We give the stellar positions, projected perpendicular to the orbital plane, shortly after the first (t≈0.5) and second (t≈6) pericentric passages in the figures; (time being given in dimensionless units corresponding to mass=l, radius=l, G=4.50). On the basis of the cooling gas inflow model, the gas will be compressed and shocked in these regions of enhanced stellar density, leading to bursts of star formation. The interval between the two successive starbursts is found to be of the same order as the trapping time needed by the galaxy to incorporate the gas ejected by stars in its cooling flow.
Dark Matter in Groups and Clusters of Galaxies
Authors: Kalinkov M. , Kuneva I. , Valtchanov I.
Published: June 2019

Samples of groups, clusters and superclusters of galaxies have been collected from existing catalogs. The group sample consisted of 70 systems, the list of clusters contains 50 systems, and there are five superclusters. Kinematical and dynamical characteristics are obtained — elongation (along the line of sight, RA and Dec), velocity statistics, total luminosity, harmonic radius, mean pair separation, crossing time, virial mass … We have compared some of the observational features with dynamical models of groups, clusters and superclusters. Aarseth's (1985) code is used.
Metal Abundances of Damped Lyα Systems and the Chemical Evolution of Spiral Galaxies
Authors: Fritze-V. Alvensleben Uta , Fricke Klaus J.
Published: June 2019

Our chemical evolution models describe in detail the enrichment process of a number of individual elements from 12C to 56Fe, including delayed SNI contributions. Variation of the characteristic timescale of star formation (SF) t∗ not only results in differences in the abundance evolution but also changes abundance ratios of elements originating from different nucleosvnthetic sites, as e.g. [C/O], [O/Fe], or [Mg/Fe].
Ultraviolet Population Synthesis of Starburst Galaxies Observed with HST
Authors: Robert C. , Leitherer C. , Heckman T.M.
Published: June 2019

Starburst galaxies are ideal laboratories to study both the physics of massive stars and processes important in galaxy formation and evolution. Observations of starburst galaxies at UV wavelengths are crucial because only in this spectral regime can we directly observe the spectroscopic signatures of the hot, massive stars that power the emission at other wavebands. UV signatures from massive stars are mainly broad spectral features (e.g. P Cygni profiles of SiIVλ1400, and CIVλ1550) formed in the stellar winds.
The reference frame of the ephemerides
Authors: Standish E. M. , Newhall X. X. , Williams J. G. , Dickey J. O.
Published: June 2019

Complete ephemerides of the moon and the four inner planets could be created solely from ranging data alone. Such ephemerides would then be independent from any outside astronomical reference system, and, therefore, would define their own unique reference frame. In fact, this is nearly the case with present-day ephemerides; the accuracy of the ranging data tends to dominate most of the least squares adjustment.

This paper outlines the process of creating the lunar and planetary ephemerides along with the orientation of the ephemerides onto the dynamical equinox. The resulting accuracies of these processes are given and a number of uses for the ephemerides are highlighted.
Fundamental radio reference frame from VLA observations of minor planets
Authors: Kaplan G. H. , Johnston K. J. , Seidelmann P. K. , Wade C. M. , Carroll T. S.
Published: June 2019

The weak thermal emission from the largest minor planets can be detected in the microwave regime by the Very Large Array (VLA). Signal-to-noise ratios are sufficiently high to permit precise measurement of the positions of these objects at all points in their orbits with respect to background extragalactic sources. We are in the process of obtaining observations of astrometric accuracy for minor planets 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygeia.

Minor planets have historically served as “test particles” in the solar system, and optical observations of these objects have been valuable in the determination of fundamental astronomical constants. In particular, optical observations of minor planets have played an important role in the establishment of the fundamental optical reference frame by permitting the determination of the orientation of the Earth's orbit relative to the stars defining the frame.

Similarly, radio observations of these bodies can play a corresponding role in the establishment of a fundamental radio reference frame. Our observations will provide a direct link between the dynamical and radio reference frames, and provide important information on the relationship between the radio and optical reference frames.
Geocentric Terrestrial Reference Frame Accuracy: DSN Spacecraft Tracking and VLBI/Lunar Laser Ranging
Authors: Niell A. E.
Published: June 2019

From a combination of 1) the location of McDonald Observatory from Lunar Laser Ranging, 2) relative station locations obtained from Very Long Baseline Interferometry (VLBI) measurements, and 3) a short tie by traditional geodesy, the geocentric coordinates of the 64 m antennas of the NASA/JPL Deep Space Network are obtained with an orientation which is related to the planetary ephemerides and to the celestial radio reference frame. Comparison with the geocentric positions of the same antennas obtained from tracking of interplanetary spacecraft shows that the two methods agree to 20 cm in distance off the spin axis and in relative longitude. The orientation difference of a 1 meter rotation about the spin axis is consistent with the error introduced into the tracking station locations due to an error in the ephemeris of Jupiter.
Predicting Universal Time from astronomical and meteorological measurements
Authors: Feissel M. , Gambis D. , Vesperini T.
Published: June 2019

Autoregressive prediction filters are tested on stationarised time series of UT1–TAI and of accumulated values of the duration of the day derived from the axial atmospheric angular momentum.
Numerical integration of precession and nutation of the rigid Earth
Authors: Kubo Yoshio , Fukushima Toshio
Published: June 2019

A numerical solution for the luni-solar precession and nutation of the rigid Earth is obtained and compared with the result from the analytical theories which are the basis of the current IAU precession and nutation formulas. We have developed a new scheme of numerical calculation by modifying the equations of motion, which enables us to avoid the numerical integration with a small step. Some errors are found in the long periodic region of nutation in the current IAU theory.
Short-term variation of the Earth's rotation and the solar activity
Authors: Djurovic D. , Paquet P.
Published: June 2019

In 1980, Feissel et al. identified a quasi–cyclic variation of 55 days in the irregularities of the Earth Rotation (ER) later detected in the Atmospheric Angular Momentum (AAM) (Langley et al., 1981). The purpose of this work is to analyse whether the causes of this cycle could lie in the physical processes of the Sun. The Wolf Numbers (WN) are used as parameters of the solar activity. Their spectral analysis over the period 1967–1985 shows such a component at 51 days. Analysis of three other periods, among which is the MERIT campaign, confirms it as well as during low or increasing solar activity periods.
The atmospheric excitation of rapid polar motions
Authors: Eubanks T. M. , Steppe J. A. , Dickey J. O.
Published: June 2019

Analysis of data from new, highly accurate, geodetic techniques reveals rapid polar motions. Comparison of the new geodetic data and meteorological excitation estimates shows that the observed rapid polar motions are correlated with atmospheric pressure changes, and that these changes are related to atmospheric normal modes.
The effect of earthquakes on the ERP during 1977–1985
Authors: Gross Richard S.
Published: June 2019

The effect on the Earth Rotation Parameters (ERP) of all the large earthquakes that occurred during 1977–1985 is evaluated. It is found that they cannot have caused the variations observed in the ERP during this time period.
Capabilities and performance of the upgraded Mark III correlator system
Authors: Whitney Alan R.
Published: June 2019

The Mark IIIA correlator system is currently operating at the U. S. Naval Observatory in Washington, D.C. in support of VLBI geodetic measurements being made by NASA, NGS, NRL, and USNO. This correlator system, developed at Haystack Observatory, is a second-generation version of the original Mark III correlator, and adds significant new capabilities such as double-speed operation, longer integration periods, and improved internal modelling.

The Mark IIIA correlator can simultaneously process up to 10 baselines of data from 5 stations. Experiments including more than 5 stations may be processed with multiple passes through the correlator. The architecture of the correlator allows a future expansion to a maximum of 16 stations. Due to a simple modular design and the low cost of required computer-support equipment, expansion is straightforward and relatively economical.

Although current geodetic VLBI observations are made using data from distant natural continuum radio sources, the Mark IIIA correlator was designed to also support processing of data collected from pulsars, artificial earth satellites, and from earth-orbiting antennas receiving signals from natural sources. These capabilities may be important in the future as efforts continue, for example, to tie satellite-related reference frames to current VLBI reference frames.

The design approach of the Mark IIIA correlator will be discussed, including its performance with respect to systematic and random errors which may affect geodetic VLBI data.
The VLB array: a new geophysical tool
Authors: Fomalont Edward B.
Published: June 2019

The National Radio Astronomy Observatory is constructing a Very Long Baseline Array (VLBA) consisting of ten antennas across the USA, between Hawaii and the Virgin Islands. The array will be a dedicated instrument for producing milliarcsecond images of radio sources. However, exciting geophysical applications of the array are obvious and, furthermore, detailed geodetic, astrometric and environmental parameters are necessary for the VLBA to achieve its full sensitivity, resolution and positional capabilities.
Determination of Earth rotation from laser ranging to Lageos and related researches
Authors: Yatskiv Ya. , Nurutdinov K. , Mironov N. , Taradij V. , Tsesis M.
Published: June 2019

The Kiev-Geodynamics-2 program complex was used for determination of earth-rotation parameters and station coordinates from the full set of the MERIT SLR data. The results have been compared with other realizations that have been reported to the Coordinating Centre at the BIH. Other researches in the reduction of SLR data and in instrumen-tation are considered.
Origin of Binary Systems
Authors: Bodenheimer Peter
Published: June 2019

Recent observational studies of the properties of binary systems among young stars indicate that the majority of binaries are formed very early in the history of a star, perhaps during the protostellar collapse. Major observational facts to be explained include the overall binary frequency, the non-negligible occurrence of multiple systems, and the distributions of period, eccentricity, and mass ratio among the individual binaries. Theoretical calculations of the collapse of rotating protostars during the isothermal phase indicate instability to fragmentation into multiple systems. This process in general produces systems with periods greater than a few hundred years, although somewhat shorter periods are possible. Fragmentation during later, optically thick, phases of collapse tends to be suppressed by pressure effects. Therefore, major theoretical problems remain concerning the origin of close binaries. Fission of rapidly rotating stars, tidal capture, and three-body capture have been shown to be improbable mechanisms for formation of close binaries. Mechanisms currently under study include gravitational instabilities in disks, orbital interactions and disk-induced captures in fragmented multiple systems, hierarchical fragmentation, and orbital decay of long-period systems. Single stars, on the other hand, could result by escape from multiple systems or by the collapse of clouds of low angular momentum, coupled with angular momentum transport after disk formation.
A Study of Ultraviolet Spectra of Delta Sagittae
Authors: Akalin A. , Engin S.
Published: June 2019

High resolution spectrum of the VV Cephei type star δ Sge (M2 II + A0 V) observed with the IUE satellite between 1979–1985 have been analysed. The radial velocity curves of non blended absorption features have been formed. Observed radial velocities are compared with the theoretical radial velocity curve due to orbital motion. We found that observed radial velocity variation is the resultant of radial velocity of hotter component and wind velocity around this star. The wind is perturbed by hotter component. Matching the UV continuum fluxes obtained from IUE high resolution spectra to fluxes of Kurucz model atmospheres yields Te=11000±500 °K. Thus the spectral type of hot component was found as A0.
The Cool Algols
Authors: Popper Daniel M.
Published: June 2019

Five semi-detached systems have been identified having detached components with spectral types G or K. These stars form a sequence having temperature decreasing with increasing mass, in contrast to the “classical” Algols with hotter detached components having properties roughly approximating those of detached main sequence stars. The status of the cool Algols is discussed briefly. A second group of 3 detached components in Algols is identified having higher temperatures than main sequence stars of the same mass.
The Outburst of Symbiotic Novae
Authors: Nussbaumer H.
Published: June 2019

We present the basic properties of symbiotic novae, and show how they differ from classical novae. Differences are observationally particularly noticeable in the luminosity curve, the rise of which is much slower, but its return to pre-outburst level takes much longer than in classical novae. Special emphasis is given to the intial phase, for which two different evolutionary paths have been observed. The outburst may lead into a supergiant phase lasting for several years, which is being followed by the nebular phase, or it may lead straight into the nebular phase. The total energy radiated during an outburst is at least as large as the energy loss of classical novae. Mass-loss during outburst may be sufficiently small to lead eventually to a supernova on the white dwarf.
Tidal Circularization Among the Close Binaries in the Halo
Authors: Torres Guillermo , Latham David W. , Mazeh Tsevi , Carney Bruce W. , Stefanik Robert P. , Davis Robert J. , Laird John B.
Published: June 2019

For a sample of halo binaries, we find that the transition between circular and eccentric orbits occurs at a period of at least 18.7 days. This is consistent with the Goldman & Mazeh theory of tidal circularization on the main sequence.
Observations of Dynamic Events in He I λ10830
Authors: Harvey Karen L.
Published: June 2019

The characteristics of large-scale two-ribbon flares and dark points observed in He I λ10830 are summarized and compared with observations of these phenomena at other wavelengths and with the underlying magnetic field.
Infrared and Submillimeter Diagnostics of Activity and Flares
Authors: Falchi A. , Falciani R. , Mauas P.
Published: June 2019

We give a critical review of the observations of solar activity in the IR and sub-mm range, which are quite scarce, except for the Fe I triplet at 1.56 μm and the Mg I emission lines at 12.32 μm. These, however, are mainly intended for solar magnetic field studies rather than physical diagnostics on activity phenomena. We compute the emission in some continuuum windows and in some detectable Paschen and Brackett lines in two extreme flare models,viz.a “chromospheric” and a white-light flare model. The utility of the Paschen and Brackett lines as diagnostics of the atmospheric state is questionable since more information can be obtained more easily by observing the higher Balmer lines. On the other hand, observations in various continuum windows can be of high scientific value and efficiency. We also discuss possible coordination with simultaneous visible observations, in order to increase the diagnostic efficiency of a prospective observing run.
Subphotospheric Convection
Authors: Stein Robert F. , Nordlund Åke
Published: June 2019

Three-dimensional simulations of solar convection are described. The simulations show that viewing convection as a hierarchy of eddies does not properly represent the large scale topology. A better picture is to view convection as a broad warm upflow with embedded cool, narrow, downdrafts. These downdrafts penetrate many scale heights through the convection zone and carry most of the net convective flux. Near the solar surface there are extremely large fluctuations in the temperature (5000-11000 K), entropy and pressure (factor of four). Radiation temperature does not provide an accurate measure of the gas temperature at a given geometric depth, because the opacity is very temperature sensitive. The emergent intensity in the infrared is smaller and has a smaller contrast than in the visible. However, in terms of radiation temperature the infrared is hotter and has a higher contrast than the visible.
Solar Oscillations Instrument at an Infrared Wavelength of 1.6 μm at Yunnan Observatory
Authors: Rufeng Li , Binxum Ye , Hailin Chen , Shaohua Liu , Bailian Deng , Jagu Ma , Hill H. A. , Oglesby P. H.
Published: June 2019

A photometric solar seismograph, as part of an international network, was installed at Yunnan Observatory, the Chinese Academy of Sciences, and put into operation in the spring of 1991. This instrument is used to detect solar oscillations by measuring the continuum radiation intensity on the solar disk with a spatial resolution of 50 arcsec, in heliocentric coordinates, for research on p-modes and g-modes when l < 50, where l is the angular degree of the eigenfunction. The solar oscillations can be observed simultaneously at two wavelengths of the detector with a sensitivity of 10 of the average intensity. This paper reports on the optical system of the instrument. Also introduced in this paper is the compensation system for the noise signals produced by the changes in the transparency of the Earth's atmosphere. This is based on solar photometry at wavelengths of 0.55 mm and 1.6 mm.
Modeling the Infrared Magnesium and Hydrogen Lines from Quiet and Active Solar Regions
Authors: Avrett E. H. , Chang E. S. , Loeser R.
Published: June 2019

The emission lines of Mg I at 7.4, 12.2, and 12.3 μm are now known to be formed in the upper photosphere; the line emission is due to collisional coupling of higher levels with the continuum together with radiative depopulation of lower levels. These combined effects cause the line source functions of high-lying transitions to exceed the corresponding Planck functions. However, there are uncertainties in a) the relevant atomic data, particularly the collisional rates and ultraviolet photoionization rates, and b) the sensitivity of the calculated results to changes in atmospheric temperature and density. These uncertainties are examined by comparing twelve calculated Mg I line profiles in the range 2.1-12.3 μm with ATMOS satellite observations. We show results based on different rates, and using different atmospheric models representing a range of dark and bright spatial features. The calculated Mg profiles are found to be relatively insensitive to atmospheric model changes, and to depend critically on the choice of collisional and photoionization rates. We find better agreement with the observations using collision rates from van Regemorter (1962) rather than from Seaton (1962). We also compare twelve calculated hydrogen profiles in the range 2.2-12.4 μm with ATMOS observations. The available rates and cross sections for hydrogen seem adequate to account for the observed profiles, while the calculated lines are highly sensitive to atmospheric model changes. These lines are perhaps the best available diagnostics of the temperature and density structure of the photosphere and low chromosphere. Further calculations based on these infrared hydrogen lines should lead to greatly improved models of the solar atmosphere.
New Atomic Data for Mg I Lines
Authors: Hoang-Binh D.
Published: June 2019

Theoretical oscillator strengths are reported for transitions between excited terms of the singlet and triplet S, P, D, F and G manifolds of atomic magnesium. The principal quantum numbers of the jumping electron range from n = 4 to 100. The calculations are based on the Coulomb approximation. Low-n results, for which other data are available previously, agree reasonably well with the sophisticated calculations of Moccia and Spizzo (1988). Data for 1,3F–1,3G transitions may deviate from hydrogenic values by as much as 50%.
Diagnostic Tools for Sunspots: the Molecules C2, Mg H and Ti O
Authors: Sinha K
Published: June 2019

The aim of the present communication is to draw attention to the value of simultaneous observations of sunspot umbrae and the quiet Sun in selected molecular lines. It is felt that such observations may lead to an array of sunspot models which account for sunspot sizes, magnetic field strengths, and the solar activity cycle.
New Infrared Measurements of Magnetic Fields on Cool Stars
Authors: Saar Steven H.
Published: June 2019

I present a preliminary analysis of IR spectra of five K and M dwarfs and two RS CVn variables. Evidence for significant magnetic flux is found on several stars, a number of which are detected for the first time. Field strengths (B) on the RS CVn variables are lower than in the active dwarfs, consistent with the concept of pressure balance limiting B in stellar photospheres. I compare the results with previous measurements.
Infrared Emission Mechanism in Large Isolated Molecules
Authors: d'Hendecourt L. B. , Léger A. , Boissel P. , Désert F. X.
Published: June 2019

The physics which governs the IR emission of a large isolated molecule (e. g. an interstellar PAH) after the absorption of an UV photon is described. We show that the simple thermal approximation is valid and we give the method to calculate emission spectra from absorption spectroscopy data.
Critical Questions for the Future
Authors: Lequeux James
Published: June 2019

All participants at this meeting agree that it has been very exciting, this for three reasons. First, it has put together astrophysicists, laboratory and theoretical physicists and also chemists, thanks to the interdisciplinary nature of the field of interstellar dust. Second, we have had a very exciting confrontation between meteolitiscists, and specialists of interstellar, and cometary dust, and we saw growing evidence that interstellar dust is a pervasive solar-system material, although the history of this dust may have been peculiar. Third, last but not least, there has been in the recent years a wealth of new data on interstellar dust emerging from observations in various wavelength ranges, especially the infrared, and a lot of new laboratory data and sophisticated theories that allow us to interpret the observations. Clearly the study of interstellar dust, which had remained in its infancy for such a long time, is becoming a mature and much less speculative field.
Inflation and the Large-Scale Structure of the Universe
Authors: Kofman L.A. , Linde A.D. , Mukhanov V.F.
Published: June 2019

Before the development of the inflationary universe scenario many cosmological problems of the standard hot universe theory remained unsolved. In particular, the origin of primordial density perturbations remained obscure.
Cosmic Structures' Formation in the Multicomponent Universe: New Tests
Authors: Lukash V. N.
Published: June 2019

Scaling of the transfer function of primordial perturbations in the multicomponent Universe is found. New tests for detecting light weakly interacting particles and dark barions are proposed.
Dynamical Evidence for Dark Matter in Individual Disk Galaxies
Authors: Athanassoula E , Bosma A
Published: June 2019

We will briefly review the following questions: 1) is there compelling evidence for the existence of dark matter in individual disk galaxies?, 2) where is this dark material?, 3) how much of it is there?, and 4) what is its shape?
Dissipation and Formation of Galactic Halos
Authors: Blumenthal George R.
Published: June 2019

When protogalaxies collapse, the cooling and infall of what will become the visible galactic component affects the mass distribution of dissipationless dark matter particles which constitute the halo. For spiral galaxies, the reaction of the dissipationless halo can have a striking effect on the resulting rotation curves [1–5].
Distortion of Cosmic Microwave Background Radiation and Decay of Weakly Interacting Particles
Authors: Sato Katsuhiko , Kawasaki Masahiro
Published: June 2019

Recently Nagoya-Berkeley group (Matsumoto et al, 1987) observed microwave radiation in the Wien region precisely and found the excess of temperature. In the previous paper (kawasaki and Sato, 1986), we investigated the distortion of the spectrum of microwave background radiation due to the radiative decay of weakly interacting massive particles. At that time, however, the distortion was not observed. In the present paper, we investigated in detail whether the decay of WIMPs can account for the observed distortion of the spectrum or not. In Fig. 1, an example is shown.
The Centaurus-Pavo Supercluster
Authors: Fairall A. P.
Published: June 2019

In the southern sky, the Centaurus and Pavo “superclusters”, although lying on opposite sides of the Milky Way, show similar redshifts (V ≃ 4500 km s−1). This author and others have suggested earlier that they may really be portions of a single entity. To investigate this further a redshift survey has been undertaken of the Triangulum Australe-Ara region (15h30m < α < 18h45m, −70° < 6 < −50°) that lies between Centaurus and Pavo, but at very low galactic latitude on the Pavo side of the Milky Way. 75 published redshifts have been supplemented by 56 new redshifts. Selection has favoured E-SO galaxies from the ESO catalogue but the varying extinction has made control difficult.
Angular Correlations of Faint (B<24) Galaxies
Authors: Jones L.R. , Shanks T , Fong R
Published: June 2019

We investigate the two point angular correlation function, ω(θ), of faint galaxy samples obtained from COSMOS machine measurements of 3.9m AAT plates. The area of sky used is the largest yet covered to very faint limits(bj<24 over 2.1 deg2 and rF<22 over 1.4 deg2). The power law slope of ω(θ) is found to be consistent with a value of −0.8 at all depths in both passbands (see fig.1). The amplitudes measured by different authors show a large scatter in the blue passband (see fig.2). If this scatter also appied to the red passband (fig.3) we conclude that although a smaller clustering amplitude in the past is preferred, it is not possible to rule out the stable clustering model, and that models in which the clustering is co-moving may be inconsistent with the data.
Galaxy Groups: Morphological Segregation Between Spirals
Authors: Giuricin G. , Mardirossian F. , Mezzetti M. , Pisani A. , Ramella M.
Published: June 2019

We have considered the sample of groups of galaxies identified by M. J. Geller and J. P. Huchra (1983, Astrophys. J. Suppl. 52, 61), omitting the groups which are part of well-known clusters or those which are probably affected by the presence of interlopers. We have searched for possible morphological segregation among spirals in galaxy groups considering the mean-pairwise distance of the members of the galaxy system and the mean distance of the members from the center of the system. All the distances are normalized to the mean-pairwise distance (MPD) and to the mean distance from the center (CD), respectively, of all the members of the groups considered. We divided the family of the spirals (plus irregulars) into two subfamilies (S′ and S″); we included in S′ the early-type spirals (with morphological type code 0≤T≤2) and in S″ the galaxies of the late morphological types (with T ≥ 3). The median values of the ratios MPD(S′)/MPD, MPD(S″)/MPD, CD(S′)/CD, CD(S″)/CD are 0.86, 1.17, 0.95, 1.08, respectively.
Galaxy Formation with Hot Dark Matter and Cosmic Strings
Authors: Brandenberger Robert H.
Published: June 2019

Hot dark matter particles have large thermal velocities at teg and hence cannot be gravitationally bound on small scales (free streaming). In models of formation of structure based on linear adiabatic perturbations all inhomogeneities on scales smaller than the maximal free streaming length λj are washed out. The mass λj inside a bail of radius exceeds the galaxy mass. Hence in the above models galaxies can only lorm by fragmentation of larger-scale objects. This is a severe problem.
The Spacetime Surrounding Superconducting Cosmic Strings
Authors: Helliwell T. M. , Konkowski D. A.
Published: June 2019

In 1981, A. Vilenkin derived the stress tensor for a straight nonconducting cosmic string of linear mass density μ oriented in the z-direction; it is given by Tμν = μdiag(1,0,0,1) δ (x) δ (y). He also showed that in linear approximation the resulting exterior spacetime is flat but conical, with deficit angle 8πGμ. Subsequently it was shown that even the exact spacetime is flat but conical. Recently E. Copeland, M. Hindmarsh, and N. Turok have derived the stress tensor

for a straight current-carrying string, where j is proportional to the current. We have used this stress tensor, together with the stress tensor of the external electromagnetic field caused by the current, to find the external spacetime of a conducting string in linear approximation. In cylindrical coordinates, the metric may be written

where h00 = 4GI2ln2r/r0 + 8Gμj2lnr/r0 = h33 + 8GI2lnr/r0, and a = 1–4Gμ–2GI2. Here r0 is the string radius and I is the electric current, related to j as described in reference 4. The linear approximation is valid as long as h0 0 and h3 3 are small compared with unity, which restricts the range of r. The (r, φ) subspace is flat but conical, with deficit angle 8πG(μ + I2/2). The spacetime reduces to that found by Vilenkin if j and I go to zero. Efforts are currently underway to find an exact exterior solution, which would apply for arbitrary values of r.
Effects of Quantum Fields Outside Cosmic Strings
Authors: Konkowski D. A. , Helliwell T. M.
Published: June 2019

The space surrounding a long straight cosmic string is flat but conical. The conical topology implies that such a string focuses light rays or particles passing by opposite sides of the string, which can have important astrophysical effects. The flatness, however, implies that the string has no gravitational influence on matter at rest with respect to the string. The flatness is a consequence of the fact that the tension along a cosmic string is equal to its linear mass density μ. There may be physical effects, however, which destroy the equality of tension and mass density, so that straight strings might after all affect matter at rest. One such effect we and others have calculated is the vacuum fluctuations of fields near the strings induced by the conical topology. Such fluctuation s are physically observable but normally small, as in the Casimir effect between parallel plates. We find the vacuum expectation value of the stress - energy tensor of a conformally coupled scalar field around a cosmic string to be

in cylindrical coordinates (t, r, θ, z). The equality of Ttt and Tzz means that the effective tension and mass density of the vacuum fluctuations are equal, so that at least in a semiclassical approximation a string dressed by such fields still has no gravitational influence on matter at rest, even though it has a substantial mass density.
Protohistoire De La Machine A Mesurer Les Cliches Astronomiques
Authors: Fauque D.
Published: June 2019

In 1864, the Rutherfurd's machine to measure stellar photographs proved the interest the astronomical photography could provide. The photographical method was developped for the observation of the transit of Venus on the Sun disc. In 1875, Brunner built a machine for this purpose; improved by the Henry's brothers, it became the prototype of the machine to measure stellar photographs ten years later. During the eighties and the nineties, other kinds of measuring machines were built; they constantly got many improvements. In 1927, for example, the Brunner's machine was remade to establish the linking catalogue.
The Third Reduction Of Giuseppe Piazzi's Star Catalogue
Authors: Proverbio E.
Published: June 2019

The star observations carried out by Giuseppe Piazzi with Ramsden's large altazimuth circle, which he began in 1792, led to the realization of a 1st and 2nd Catalogue, published by Piazzi in Palermo in 1803 and 1814.

During 1845, the original astronomical observations in Piazzi's catalogue, included in “La storia celeste of the Palermo Observatory from 1792 to 1814”, which had been kept at the Brera Observatory in Milan, were published in Vienna.

The publication of these observational data revealed a series of errors, real or presumed, which cast doubt on the reliability of the Palermo Catalogue.

Towards the end of the last century, upon the suggestion of Giovanni Schiaparelli, work on the reduction of Piazzi's catalogue was once again taken up for the purpose of producing an independent catalogue based on the original observations. This work, carried out by Francesco Porro, led to the production of a corrected catalogue purged of systematic and accidental errors.

The third fundamental star catalogue of Palermo may represent the basis for the final reduction of the great Palermo Catalogue of 7646 stars.
“Petite histoire” du Congrès astrophotographique de 1887
Authors: Motais de Narbonne A.M.
Published: June 2019

Details of the organization of the 1887 astrophotographic congress have been traced in Paris Observatory archives. The following points have been especially examined: invitations, practical organization, budget, decorations and reports edition. Amiral Mouchez personality becomes apparent after the factual knowledge.
Mapping Coordinate System Irregularities On The Celestial Sphere
Authors: Hemenway Paul D. , Whipple Arthur L. , Duncombe Raynor L.
Published: June 2019

Various techniques have been used to evaluate and describe coordinate system irregularities. The basic techniques have developed from simple differences to differences in coordinate “bins” to full spherical and cylindrical harmonic treatments. We are undertaking a 15-year program of minor planet observation with the express purpose of finding basic parameters of the adopted fundamental system with respect to a dynamical reference frame. The program is expected to provide a few hundred observations per year of 34 minor planets selected for their distribution of physical and orbital characteristics. The ability of the program to contribute to our knowledge of the rotation of the fundamental system and systematic irregularities within the system will depend on the accuracies of the observations and the distribution of the observations over the orbits and over the celestial sphere. We are considering the use of splines as a method of evaluating systematic corrections to the extant fundamental system. The initial development of the formalism and prospects for evaluation are presented.
Radio Continuum Surveys Of The Sky
Authors: Wielebinski R.
Published: June 2019

Radio continuum surveys give us the fundamental information about the distribution of the radio intensity across the sky. The radio waves originate in three fundamental emitting processes and are measured superposed in the antenna beam. At the lowest radio frequencies (below 10 GHz) the nonthermal emission process (synchrotron radiation) predominates. This radio emission comes from supernova remnants, from the “galactic background” (relativistic electrons diffusing in galactic magnetic fields), but also from extragalactic objects (galaxies, quasars, radio galaxies, etc.). In the frequency range 10 GHz < f < 300 GHz the thermal (free-free) process becomes dominant. In the Galaxy we see the HII regions along the galactic plane. In nearby galaxies we can identify the thermal emission in the disks. Above 300 GHz the dust is seen. This is the boundary region between radio and far-infrared radiation.
Optical Positions And Proper Motions Of Selected Radio Stars
Authors: Schwerdtfeger H.M. , Hering R. , Walter H.G. , Jahreiß H.
Published: June 2019

From a list of 275 confirmed or potential radio stars proposed to the Hipparcos input catalogue we selected about 80 objects which either lie outside the conventional astrometric catalogues or which are SAO-stars having declinations less than −17°. The positions of these stars were derived from measurements on POSS, SRC, and ESO(B) plates using reference stars from the SAO catalogue for the northern candidates, and from the Perth 70 catalogue for the southern candidates, respectively. The epochs of our positions fall in the middle of the fifties and seventies. For 52 stars other epochs were supplied by observations taken from literature. We determine proper motions from these positions which provide a base-line up to 35 years.
Planetary Nebulae Symposium - Introductory Remarks
Authors: Terzian Yervant
Published: June 2019

It seems proper to start our Symposium from the very beginning. The oldest known discovery of a planetary nebula dates back to Messier who in 1764 catalogued the Dumbbell nebula, NGC 6853, as Messier 27. Only 100 years later Huggins discovered the emission line spectra of planetary nebulae and he pointed out that his discovery proves that these objects are not clusters of stars but are “enormous masses of luminous gas or vapor”. In 1887, a curious suggestion was made by Lockyer who thought that the nebulae were clusters of burning meteorites when he incorrectly identified three nebular emission lines with magnesium.
Planetary Nebulae in the Andromeda Galaxy and its Companions
Authors: Ford Holland C.
Published: June 2019

The identification and observation of planetary nebulae in the Andromeda galaxy (M31) and its companions provide a powerful means of studying their old stellar populations. The direct determination of chemical abundances and radial velocities for even the brightest individual old stars is impossible at the distance of M31. The strongest emission lines of planetary nebulae are as bright as the entire visual continuum of the most luminous giants. Consequently, spectrophotometry of planetary nebulae presently provides the only direct measure of chemical abundances, and, with the exception of globular clusters, the only radial velocity determinations for the old populations.
New and Misclassified Planetary Nebulae
Authors: Kohoutek L.
Published: June 2019

Since the “Catalogue of Galactic Planetary Nebulae” 226 new objects have been classified as planetary nebulae. They are summarized in Table 1 which gives the designations, names, coordinates and the references to the discovery. Further 9 new objects have been added to Table 1 and called 1proto-planetary nebulae1, but their status is still uncertain. Only 34 objects have been included in the present list of misclassified planetary nebulae (Table 2) although the number of doubtful cases is much larger.
Advances in Optical Studies of Planetary Nebulae
Authors: S. Miller Joseph
Published: June 2019

This review will contain a brief survey of a few of the issues that have been the concern of optical studies of planetary nebulae since the last IAU Symposium on this subject in 1967. Also included will be a short discussion of advances in optical instrumentation and remarks on some selected important problems which should be the concern of future optical investigations of planetaries.
Advances in Studies of Physical Processes
Authors: Seaton M.J.
Published: June 2019

The forbidden lines in planetary nebulae are due to transitions between energy levels belonging to configurations ns2npq with q = 1 to 5, and with n = 2 ([O II], [O III], …) or n = 3 ([S II], [S III], …). For electron impact excitation of these levels, the expansion
On the Variability of the Planetary Nebulae
Authors: Kostyakova E.B.
Published: June 2019

The study of several planetary nebulae, suspected earlier of variability, was continued during the last years at the Sternberg Astronomical Institute.
Symposium Conclusions I
Authors: Osterbrock D.E.
Published: June 2019

As I am sure you realize I cannot really give you conclusions, I can only give you my own impressions of this conference; George Field will give you his impressions, and you must draw your own conclusions from all that you have heard here.
Markarian galaxies in the vicinity of the Coma cluster
Authors: Arakelian M. A.
Published: June 2019

The distribution of Markarian galaxies in annular zones at different angular distances θ (degrees) from the centre of the Coma cluster is shown in the Table. the coordinates of the centre for the equinox 1950 are assumed to be α = 12h57m.5, δ = 28°15′. the third, fourth and fifth columns of the Table contain the number of Markarian galaxies in each zone, the solid angle in square degrees and their mean surface densities respectively. It can be seen that an excess surface density of Markarian galaxies exists not only in the very central zone I but in the annular zone II as well. Indeed, the ratio n/ω in zone II is more than twice the value corresponding to the whole area surveyed (and to zones III and IV).
On the methods of discovering groups and clusters of galaxies
Authors: Fessenko B. I.
Published: June 2019

Groups. Even if real groups did not exist, the investigation of large regions of the sky will reveal other dense clumpings of galaxies. the usual estimate of the number of optical members in these clumpings will confirm their reality. But let us remember that all these groups are false. False groupings of galaxies should emerge in large numbers because of the effects of interstellar absorption and of variability of the observating conditions. Statistical considerations of the groups detected by Turner and Gott (1976, Ap. J., Suppl. Ser., 32, 409) leads to the conclusion that the percentage of false groups members is equal to 40% or more.
A survey programme for QSO and related objects
Authors: Lorenz H.
Published: June 2019

I would like to give the first results of a survey programme for high redshift quasars and related objects on the Tautenburg-Schmidt plates. It is known that objective prism plates are very useful for detecting these objects. the smaller the dispersion of the spectra, the fainter are the objects that can be found. Our Schmidt correcting lens gives spectra with the dispersion of 2500 Å mm−1 at Hγ. the limiting magnitude is about 19m in the B range. At this very low dispersion reliable classification of the objects requires the extraction of all the information stored on the plate. That means that a quantitative evaluation should supplement visual insepction.