bluuebunny/crossref_metadata_2025 huggingface dataset:
Observational Data on Star Formation in Cepheus A
Authors: Hughes V. A.
Published: June 2019

Cep A is a condensation in the larger CO cloud originally mapped by Sargent (1977, 1979), and contains radio H II regions, OH and H2O masers, a far infrared luminosity of 2.5x104 L⊙, anisotropic mass outflow as seen originally in CO but later in other molecular lines, and a Herbig-Haro object.
Star Formation in the Southern Spiral Arm of M31
Authors: Ichikawa T. , Nakano M. , Tanaka Y. D.
Published: June 2019

Conspicuous dust lanes define the spiral arm in the south of M31. The integrated HI line emission map shows several large cloudlike structures with sizes ranging from hundreds to thousands of parsecs, forming a spiral arm along the dust lanes (Figure 1). To investigate how such super clouds correlate with star formation phenomena, we present in Figure 2 a compilation of published data on: CO emission, dark clouds, HII regions, OB associations, and thermal infrared radiation from IRAS. The CO emission distribution is similar to that of HI and also forms large cloudlike structures. The large CO clouds P, Q, and R, which are located in the high density HI areas, have bright HII region complexes of several hundred parsecs at their outer edges. Further out large OB associations are found. In contrast, cloud B, which shows weaker CO emission, has a large and diffuse HII region which may be relatively old. This giant HII region is located in a large hole of HI and dark clouds (Brinks 1981). The IRAS maps show strong correlated thermal emission from the dust lanes. The luminosity from the star formation activity heats the dust in the molecular clouds. The local peaks at A, P, and Q in the 25 μm band, extending 200-300 pc, have revealed the existence of massive young stars embedded in the clouds.
Star Formation in M81
Authors: Bash Frank , Kaufman Michele
Published: June 2019

VLA observations of the spiral galaxy M81 in the radio continuum at wavelengths of 6 and 20-cm have been used to check the predictions of the density wave theory. The non-thermal radiation from the arms has been detected and the arms are found to be broader than the predictions of the classical density wave theory. Their width does seem to agree with that predicted by models which take the clumpy nature of the interstellar medium into account. These data are also able to separate giant HII regions from the non-thermal arms. Collaborators have furnished optical Hα data on the HII regions and HI 21-cm data, from the VLA, which will be used to find and measure the location of the HII regions with respect to the spiral shock wave and to measure the visual extinction in the disk of M81.
A New Strong Extragalactic OH Megamaser in the Infrared Source IRAS 17208 −0014
Authors: Bottinelli L. , Dennefeld M. , Gouguenheim L. , Martin J. M. , Paturel G. , Le Squeren A.M.
Published: June 2019

The powerful OH megamasers detected in IC4553 (Baan et al. 1982), NGC3690, Mrk231 (Baan, 1985; Kazès and Dickey, 1985) and Mrk273 (Bottinelli et al. 1985a) show several common properties; in particular, they are strong IR emitters. We have thus undertaken a study of the strongest far IR (100 μm) uncatalogued IRAS sources and we report here on the discovery of a new strong extragalactic maser in the IR source IRAS 17208 −0014 (Bottinelli et al., 1985b)
The New 4-m Millimeter Wave Telescope at Nagoya
Authors: Kawabata K.
Published: June 2019

A new 4-m millimeter wave telescope has been constructed at the Department of Physics and Astrophysics, of Nagoya University, mainly for the purpose of making rapid surveys of interstellar molecular lines. The observing site is located on the Higashiyama Campus of the University at an altitude of 70-m above sea level in Nagoya. Observations with this telescope started in December 1983.
The Stellar Population of a Typical Globular Cluster
Authors: Pecci F. Fusi , Clementini G.
Published: June 2019

We discuss typicalities and atypicalities in the stellar population of a Galactic globular cluster.
Early-Type Stars
Authors: Freeman K.C.
Published: June 2019

Away from the young disk, several classes of early type stars are found. They include (i) the old, metal-poor blue horizontal branch stars of the halo and the metal-poor tail of the thick disk; (ii) metal-rich young A stars in a rapidly rotating subsystem but with a much higher velocity dispersion than the A stars of the young disk, and (iii) a newly discovered class of metal-poor young main sequence A stars in a subsystem of intermediate galactic rotation (Vrot ≈ 120 km s−1). The existence and kinematics of these various classes of early type stars provide insight into the formation of the metal-poor stellar halo of the Galaxy and into the continuing accretion events suffered by our Galaxy.
Central Black Holes and Dark Halos in Elliptical Galaxies
Authors: De Zeeuw P.T.
Published: June 2019

Studies of the mass–to–light ratio M/L as a function of radius in a galaxy usually focus on: a) the existence of dark matter in and around galaxies, and b) the presence of massive black holes in their nuclei. Here we concentrate on elliptical galaxies, and summarize some recent work in both areas. We refer to more extensive reviews for earlier developments (Schwarzschild, 1954; Trimble, 1987; Ashman, 1992; Kormendy, 1993). A third area of interest is the behavior of the stellar populations as a function of radius, and its effect on M/L (e.g., Peletier, 1989). We will not discuss this here.
The Stellar Ages of Elliptical Galaxies
Authors: Faber S.M. , Trager S.C. , Gonzalez J.J. , Worthey Guy
Published: June 2019

Integrated broad-band colors and metallic lines cannot discriminate clearly between the effects of age and Z in old stellar populations. Such data are more sensitive to Z than to age. The Hβ feature provides a way to break this degeneracy. New measurements indicate that the mean stellar ages of typical E galaxy nuclei are fairly young, ranging from 2 to ~12 Gyr. The outer parts of E galaxies are both older and more metal-poor than nuclei, consistent with the formation of E galaxies via mergers and starbursts. Age effects contribute strongly to the classic color-line strength sequence of E galaxies.
Stellar Populations in S0 Galaxies
Authors: Bender R. , Paquet A.
Published: June 2019

The study of stellar populations in external galaxies has so far concentrated on elliptical galaxies, spirals and a few dwarf galaxies, while S0 galaxies found only relatively little attention (with a few notable exceptions, e.g., Gregg, 1989; Bothun and Gregg, 1990). This is astonishing because S0-galaxies offer a unique possibility to study (a) old disk populations outside our own galaxy, (b) the properties of bulges in external galaxies without contamination by blue disk stars, and (c) the gradual change of the stellar populations of galaxies as a function of disk-to-bulge ratio. Last but not least, the comparison of the stellar populations of ellipticals, spirals and S0 galaxies allows to re-iterate on the question whether S0's are principally similar to spirals but have just stopped forming stars earlier, or, whether they form an class intermediate between ellipticals and spirals (e.g.Larsonet al., 1980; van den Bergh, 1994).
The Vertical Structure of the Galactic Disc
Authors: Haywood M. , Robin A.C. , Bienaymé O.
Published: June 2019

We have analyse star-count data in the direction of the Galactic Poles using a model of stellar population synthesis (Robin & Crézé (1986), Bienaymé, Robin & Crézé (1987)). The HR diagram for disc stars in the model is computed for a given star formation rate history and initial mass function (Haywood, 1994). In a paper submitted to A&A (Haywood et al.), we give a detailed investigation of the effects of these two functions on the simulated star-counts, and compare these with observed V, B-V data from V=5 to 22. We have obtained new constraints on the SFR, which we show has remained constant (to within a factor <3) since the disc formation, and on the IMF in the intermediate mass range (1-2 M⊙). Finally, we also obtain new constraint on the increase of vertical velocity dispersion with age. We state that if the disc does not containt any dynamically important dark mass, then this relation saturates at value smaller than 21 km.s−1.
The Age of the Galactic Inner Halo
Authors: Fullton Laura Kellar , Carney Bruce W.
Published: June 2019

Are the inner regions of the Galaxy younger, older or the same age as the outer halo? We have undertaken a study of globular clusters which lie within 4–5 kpc of the Galactic center. Here we present results for three of these clusters: NGC 6723, NGC 6352 and NGC 5927. We have constructed cluster color-magnitude diagrams from which we have determined their ages using the magnitude difference between the horizontal branch and main-sequence turnoff following the procedure of Carney, Storm & Jones (1992, CSJ). We find that 47 Tuc, NGC 6352 and NGC 6723 are coeval to within the errors, while NGC 5927 appears younger. The figure below is a reproduction of Figure 20 of CSJ with our clusters added.
Mapping the Stellar Distribution in Globular Clusters: An Application to NGC 6809 = M55
Authors: Zaggia S. R. , Piotto G. , Capaccioli M.
Published: June 2019

The principal aim of this work is to map the stellar distribution of a large sample of galactic globular clusters from the central regions to the outer envelope (beyond the tidal radius for an estimate of the foreground/background contamination) with a good statistical sampling of stars in the different branches of the color-magnitude diagram and with different masses. These new data will be used to investigate the dynamical evolution of stellar systems embedded in the gravitational field of our Galaxy, and, eventually, to set constraints on the mass distribution of the Milky Way. In this context, star counts have been carried out on V and I CCD frames of the rich, low concentration galactic globular cluster M55. The frames cover 35% of the cluster, from the center to 1.3 times the tidal radius (with total coverage inside 1rc). From V=14 (i.e. the horizontal branch level) to a limiting magnitude V=22 (MV = 7.9), a total of 36800 stars have been measured. A population of blue stragglers (BS) has been identified, but, at variance with other clusters of similar core concentration, the BS of M55 are only marginally more concentrated toward the center. No population gradient has been identified in M55. A luminosity function down to V = 21.3 has been obtained, after applying completeness and field star contamination correction to the star counts. The mass function is very flat (xglobal ≤ −0.5), as it was expected for this cluster located close to the galactic center and to the galactic disk. A single mass King model fitted to the radial star counts gives a core radius rc = 143″ and a tidal radius rt = 970″, ~ 10% greater than previously estimated.
Blue Galaxies in Distant Clusters
Authors: Jablonka P. , Alloin D.
Published: June 2019

We analyzed – in terms of age and metallicity – the stellar content of blue galaxies in 3 distant clusters at z ~ 0.3. We found that they contain a more metal-rich population than nearby late-type spirals.
The Earth's variable rotation: some geophysical causes
Authors: Lambeck Kurt
Published: June 2019

The Earth's variable rotation, its departures from what it would be if it were a rigid body rotating in isolation, has occupied the interest of astronomers and geophysicists for more than 100 years. The reason for this is quite clear when one becomes aware of the range of processes that perturb the Earth from uniform rotation (Figure 1). A complete understanding of the driving mechanisms requires a study of the deformation of the solid Earth, of fluid motions in the core and the magnetic field, of the mass redistributions and motions within the oceans and atmosphere, and of the interactions between the solid and fluid regions. The discussion of evidence for the variable rotation includes the examination of not only a variety of optical telescope evidence that goes back some 300 years, but also of historical records of lunar and solar eclipses, and planetary occultations and conjunctions for perhaps the past three millenia. The geological record, in the form of fossil growth rhythms in organisms such as corals, bivals or brachiopods or as cyclic organic growth and sediment sequences such as stromatolites or banded iron formations, extend, albeit with considerable uncertainty, the record back through Phanerozoic time and into the Early Precambrian. To this variety of measurement techniques now has to be added the new methods derived from the space-oriented technological developments of the past few decades.
Status of the realization of the BIH Terrestrial System
Authors: Boucher C. , Altamimi Z.
Published: June 2019

A new realization of the BIH Terrestrial System, using space information (VLBI, LLR, SLR, Doppler), was published in the BIH Annual Report for 1984, under the name BTS 84. Details about the analysis, as well as comparisons between BTS 84 and BTS 85, and between BTS 85 and other individual systems, are presented. A study of origin, scale and orientation characteristics of BTS with regard to other systems is given. Further improvements of the model, taking time-like variations into account, are also outlined.
Polar motion from ILS observations with least-squares collocation
Authors: Verbeiren R.
Published: June 2019

Least-squares collocation is a powerful method for combining interpolation, filtering and parameter determination in one single computational step. We show that the method is applicable to the computation of polar motion values from a very large set of basic observational data. In this study, we use the ILS observations from 1900 to 1978.
Observations of Solar Oscillations in He I 10830 Å
Authors: Fleck B. , Deubner F.-L. , Maier D. , Schmidt W.
Published: June 2019

In continuation of a series of studies devoted to the dynamics of the solar photosphere and chromosphere we have attempted to further extend the range of heights in the atmosphere towards the transition region by including observations of the He I 10830 line. We have recorded simultaneous time series of He I 10830 and Mg I 8807 spectra in the quiet solar atmosphere using the echelle spectrograph at the German Vacuum Tower Telescope in Izaña, Tenerife. The velocity signal derived from the Doppler shifts of He 10830 clearly reveals oscillatory motions. The intensity of He 10830, on the other hand, is hardly affected by the oscillations. In the cell interior the 3-min oscillations prevail. Longer periods are found ain the cell boundaries of the chromospheric network where He absorption is enhanced. The V–V phase difference spectrum between the oscillations of He 10830 and those of Mg 8807 confirms previous observations of a non-propagating component that dominates the acoustic wave spectrum in the chromosphere.
Computation of Infrared Hydrogen Lines
Authors: Carlsson Mats , Rutten Robert J.
Published: June 2019

We compare infrared hydrogen lines observed with ATMOS with computations for two models of the solar atmosphere, one without and one with a chromosphere. The weaker H I lines are formed in the photosphere. Proper evaluation of Stark broadening is required to reproduce their profiles; the heavy ion contribution is most important. The cores of the stronger lines are sensitive to the structure of the chromosphere, but detailed NLTE modeling is needed for diagnostic applications.
The Thermal and Magnetic Structure of Sunspots
Authors: Maltby P.
Published: June 2019

The continuum intensity observations of sunspot umbrae and penumbrae in the visible and infrared are reviewed. The intensity in the darkest part of the umbra and the average penumbral intensity are known with relatively high accuracy inlargesunspots. The importance of including infrared observations in the construction of semi-empirical sunspot models is emphasized.

Magnetic field measurements are discussed. Special attention is given to recent high-spatial-resolution observations that show large fluctuations in magnetic field inclination, suggesting that the sunspot magnetic field changes its inclination – but not its magnitude – between bright and dark penumbral features.
Physical and Chemical Properties of Polycyclic Aromatic Hydrocarbons
Authors: Leach S.
Published: June 2019

A review is presented of some physical and chemical properties of polycyclic aromatic hydrocarbons (PAHs) that are relevant for interpreting various aspects of observations and speculations on PAHs in the interstellar medium. The subjects discussed are: the stability and reactivity of neutral and ionic PAHs; the spectroscopy and photophysics of neutral and monocationic PAHs; the photostabilities of PAH monocations and dications and their astrophysical implications.
The Core-Mantle Model of Interstellar Grains and the Cosmic Dust Connection
Authors: Greenberg J. Mayo
Published: June 2019

Historically there have been two different types of grain modelling: One of these basically uses particle populations which evolve essentially by coagulation (e. g., the MRN model: Mathis, Rumpl and Nordsieck, 1977); the other considers the physical and chemical evolution of the particles with a particular emphasis on changes not only in sizes but also in chemical and morphological structure (e. g. Greenberg, 1978; Williams, 1989). The model of Oort and van de Hulst (1946) was the first to consider that grains must evolve in interstellar space by treating both growth and destruction in clouds. The chemical properties had already been derived by van de Hulst (1946) and then later described as the dirty ice model which consisted of the saturated moleculesH2O, CH4andNH3with trace constituents of other atoms and molecules resulting from surface reactions of atoms on the grains. How such grains could nucleate was left as an unsolved problem but the fact that, once formed, there did not seem to be any reason why they should not grow until they exhausted the condensable atoms in the gas led to the suggestion that a limiting destructive mechanism must be provided. This was assumed to be by grain-grain collisions within clouds moving at relative speeds of 10 km s−1. We thus had the first dynamical theory leading to a steady state distribution of grain sizes. This model provided for me the starting point of the core-mantle model of grains. The observations of the 60's and henceforth clearly showed the existence of other types of small particles, which have been invoked to explain the 2200 å hump (Stecher and Donn, 1965), the far ultraviolet (FUV) extinction (Greenberg and Chlewicki, 1983), and now certain infrared emission features. These other components notwithstanding, grains still account for the major fraction of the solid particle mass in space.
Interstellar Molecules in Meteorites
Authors: Kerridge J. F.
Published: June 2019

Substantial enrichment of deuterium, D, in certain components of chondritic meteorites is interpreted as a record of isotopic fractionation during ion-molecule reactions at the very low temperatures characteristic of dense interstellar clouds. Whether those meteorites still contain the actual molecules that were synthesised in the presolar interstellar medium, or whether the interstellar material was recycled into a later generation of molecules within the early solar system is not known.
Some Critical Remarks on the Inflationary Universe Concept
Authors: Börner Gerhard
Published: June 2019

The basic idea of inflation in cosmology is very simple: It is the assumption that the expansion factor R(t) of a Friedmann-Lemaltre cosmological model grows exponentially during a brief time interval in the very early universe. The phase of exponential growth is followed by a thermalizatlon stage and a subsequent “normal” evolution R(t)∼vt. This “Inflationary expansion“ can help to solve cosmological puzzles inherent in the standard model - such as the large-scale flatness, the horizon structure, the numerical value of the entropy in a comoving volume [for a review see Brandenberger 1985]. To turn this romantic idea of inflation into a quantitative model requires still a lot of work: The simple change in the thermal history of the universe must be derived from a fundamental particle theory. The models proposed so far do not inspire much confidence. In the following a few difficulties of the Higgs field idea, especially the Coleman-Weinberg formalism will be pointed out (section 1). In section 2 some problems connected with the investigation of initially strongly anisotropic or Inhomogeneous cosmological models will be mentioned.
Giant Luminous Arcs in Clusters of Galaxies
Authors: Lynds Roger , Petrosian Vahè
Published: June 2019

During a program of study of surface brightness of elliptical galaxies in large redshift clusters in 1976 by a video camera at the KPNO 4-meter telescope, we in colaboration with Alan Sandage discovered filamentary and arc-like features in three clusters of galaxies. More recently, the same clusters (Abell 370, Abell 2218, and Cl2244-02) were observed by three different CCD's at the same telescope. These new observations confirm ouir old observations, and being of higher quality, show that the features in two of the clusters (Abell 370 and Cl 2244) form well defined continuous arcs with the following properties:

1)

Large nearly circular features (length and radius of curvature ∼100 Kpc) with the center of curvature located near the center of gravity of the cluster.

2)

Large optical luminosity (≃1011L⊙).

3)

Bluer than the elliptical galaxies with unexpectedly high ultraviolet emission for Abell 370 giving rise to an unusual spectrum (see figure 1).

4)

Nearly uniform width along the arc with almost abrupt termination points, indicating a one dimensional structure rather than projection of a portion of a spherical shell.

5)

the arcs are nearly resolved perpendicular to their length with widths of ≤ 1″ (≤ 6 Kpc).

i)

In case of Abell 370 the surface brightness is very uniform but the width varies with wavelength, becoming wider toward blue and ultraviolet.

ii)

In case of CI 2244 there is considerable variation of surface brightness along the arc. We have no information on the variation of the width with wavelength.

6)

Our data does not show any other unusual features associated with the clusters as a whole or with the giant cD galaxies. These clusters may, however, be unusual in that they seem to have two distinct centers of gravity, this is especially true for Abell 370 which has two almost identical giant cD galaxies instead of the usual clusters dominated by one centrally located cD galaxy.

7)

Polarization observations show that the arcs are not highly polarized (polarization < 20%).

8)

From a short exposure spectral observation of C12244 we can only deduce absence of very strong emission lines.
Cosmological Implications of the Fifth Force
Authors: Fujii Yasunori
Published: June 2019

A brief review is given on the present status of the “fifth force”, followed by the study of its cosmological consequences. If the force is indeed mediated by a massive vector field, we expect a period t ≲ 10−13 sec in which the universe cooled down like T ∼ t−1.
Vacuum Polarization and Scalar Field Effects in the Early Universe
Authors: Gottlöber S. , Müller V. , Haubold H. J. , Mücket J. P.
Published: June 2019

Talcing into account vacuum polarization effects and a coherent massive scalar field we consider a singularity free cosmological model from which an intermediate inflationary stage follows quite naturally. According to the ideas of Tryon, Fomin, Zeldovich and others on the spontaneous creation of an universe by a quantum process the newly created universe must be closed. Its evolution starts from a finite initial value a of the order of the Planck length with a zero velocity ho = 0 (h - Hubble parameter). Therefore, in this moment an effective source term not fulfilling the strong energy condition must be dominant. It can originate fron a coherent massive scalar field (mass m) with zero kinetic energy and/or the vacuum polarization (considered here in the form of a modified gravitational Lagrangian with quadratic terms of the Ricci scalar). The corresponding general Lagrangian reads (c = h =1)

where ∝ is a negative coupling constant and Lmat is the Lagrangian of other possible existing matter. Both the massive scalar field and the vacuum polarization effects drive the universe to expand exponentially for a definite time interval depending on the initial radius a0 and the parameters m and ∝, during which all other matter being originally present is diluted. The following small oscillations superimposed on the dust-like power law behaviour of the scale factor cause an intensive particle production, and the universe heats up to a radiation dominated Friedmann universe. This process must terminate before baryogenesis. The matching of the different phases of the cosmological evolution and the requirement to fit the parameters of the observed universe lead to a definite parameter range for m and |∝| well below the Planck values. In consequence the present mass density must be equal to the critical one (Ω = 1) with high accuracy.
Cross-Correlation Analysis of Galaxies with Different Luminosity
Authors: Xia X.-Y. , Deng Z.-G. , Liu Y.-Z.
Published: June 2019

In the former work (Xia, Deng and Zhou, 1986), we have showed by two- point correlation analysis that more luminous galaxies cluster stronger. Now we present the result of cross-correlation analysis for galaxies with different luminosity. This analysis supplies information about the relations between the distributions of galaxies with different luminosity. The analyses are based on the data given by CfA survey and have made the same corrections as in the former work. The samples are divided into three subgroups in absolute magnitude ranges: a) −21–22, b) −20–21 and c)−19–20. We make the cross-correlation analysis for each two subgroups. Fig. 1 gives the obtained cross-correlation function ξc(r) and Fig. 2 shows the log ξc(r)-log r diagram, the straight lines in Fig. 2 are given by linear regression. These results show that the two brightest subgroups have the strongest correlation. Combining with the results of former work, it follows that the probability of two brighter galaxies being close to each other is larger than that of fainter galaxies.
Path Integral Methods for Primordial Density Perturbations
Authors: Bertschinger Edmund , Gelb James M.
Published: June 2019

Path integrals may be used to describe the statistical properties of a random field such as the primordial density perturbation field. In this framework the probability distribution is given for a Gaussian random field subjected to constraints such as the presence of a peak of given curvature at a specific location in the initial conditions. An algorithm has been constructed for generating samples of a constrained Gaussian random field on a lattice using Monte Carlo techniques. The algorithm is equivalent to, but much faster than, generating unconstrained random samples repeatedly until a sample is found satisfying the desired constraints to arbitrary precision. The method makes possible a systematic study of the density field around peaks or other constrained regions in the biased galaxy formation scenario and it is effective for generating initial conditions for N-body simulations with rare objects in the computational volume.
Oriental Star Maps
Authors: Stephenson F. Richard
Published: June 2019

The development of celestial mapping in China is discussed with particular regard both to the accuracy of construction and present-day utility of star maps from the pre-Jesuit period.
Naissance Et Developpement De La Carte Du Ciel En France
Authors: Weimer Théo
Published: June 2019

This is a summary of the publication “Brève histoire de la Carte du Ciel en France”. Th. Weimer, Observatoire de Paris Pub., 1987.
Astrographic Catalogues Of British Observatories
Authors: O'Hora Nathy P J
Published: June 2019

At the International Congress of Astronomers that met in Paris, in 1887, to plan the mapping of the sky by photography, British observatories undertook the photography of approximately quarter the sky. This paper describes the contribution to the Astrographic Programme of these observatories and of other British establishments that subsequently offered to participate in the project.
Compilation Of The Nirs Using The Eichhorn Method
Authors: Cole C.S.
Published: June 2019

The Eichhorn method of simultaneously estimating both target parameters and model parameters is applied to the compilation of a complete star catalogue. The input material of the Northern International Reference Stars (NIRS) is used and the resulting catalogue is compared to the NIRS catalogue compiled by Corbin (1977) using traditional techniques. By simultaneously using all available constraints on all available data, it is shown that the new estimates of the star parameters have smaller formal errors than estimates derived from the same material but using conventional procedures. Both versions of the NIRS are used to predict the star positions of the later observed Perth 70: A Catalogue of Positions of 24900 Stars and these predicted positions are compared to the actual observed positions. It is found that a simultaneous reduction results in a slight but significant improvement in the declination system of the NIRS.
The Parallax And Proper Motion Program Of The Shanghai Observatory 1.56-M Astrometric Reflector
Authors: Jia-ji Wang
Published: June 2019

The main properties of the 1.56-m astrometric reflector of Shanghai Observatory are described. Some principles of selecting program stars are presented. The experimental program that has been performed with the Zô-sè 40-cm refractor since 1980 is outlined. Accuracies which are expected to be obtained for new program parallaxes are discussed.
Optical Determination In The Positions Of Radio Stars
Authors: Tong-qi Xu , Pei-zhen Lu , Zong-yuan Chu , Shu-he Wang
Published: June 2019

Optical positions of 16 radio stars have been derived from 40 cm astrograph at Zô-Sè. The reference catalogues are AGK3 and SAO, the average mean square error of single observation is 0″.058 in the right ascension and 0″.053 in declination. The magnitude difference has no significant effect on the observations.
The Planetary Nebula in the Fornax Dwarf Galaxy
Authors: Danziger I.J. , Dopita M. , Hawarden T.G. , Webster B.L.
Published: June 2019

A planetary nebula has been identified near the center of the Fornax dwarf elliptical galaxy. Quantitative spectrophotometry reveals that it is slightly reddened, and belongs to an intermediate-excitation class, with a normal helium abundance. Since the abundances of all 2 to 3 times lower than in the Orion nebula, the material in the nebula which has a mass ≥ 0.1 M probably represents at least a second generation of processed matter. The implications of this conclusion are briefly discussed from the point of view of heavy element enrichment in low mass systems such as Fornax whose mass is 2×107 M. (Paper will appear in The Astrophysical Journal.)
A New Synthetic Distance Scale for Planetary Nebulae
Authors: Acker Agnès
Published: June 2019

A new distance scale is provided for the Planetary Nebulae (PN). It combines thirteen lists, published between 1950 and 1976, for which the distances have been recalibrated with the aid of a large number of individual distances Dind: 19 values were selected from among individual distances already published, and 62 new distances have been calculated from kinematic and absorption laws.
The Electron Temperature in the He++ Regions in Planetary Nebulae
Authors: Tylenda R.
Published: June 2019

A method of determination of the electron temperature in the He++ regions in planetary nebulae from observed intensities of [NeV] λ3426 and [NeIV] λ4714–25 relative to HeII λ4686 is presented. It has been used for 22 planetary nebulae for which the observational data have been taken from Kaler's Catalogue (Ap. J. Suppl., 31, 517). The electron temperatures in the He++ regions range from 15,000°K to 30,000°K for most of the studied planetaries and are usually significantly higher than the temperatures determined from [01II] lines which refer to the He++ regions. A correlation between the electron temperatures and effective temperatures of central stars has been found; the planetaries with hotter nuclei have slightly higher electron temperatures in the He++ regions. Finally, intensities of ultraviolet lines of [NeV] λ2975 and [NeIV] λ2424 have been predicted for the studied nebulae.
The Absorption of Hell Lyα Photons in Planetary Nebulae
Authors: Flower D.R. , Perinotto M.
Published: June 2019

The fate of the Hell Lya photons, produced during recombinations of the He++ ions and electrons, is important in considerations of the ionization and thermal structure of high excitation nebulae (Flower, 1968, IAU Symp. No. 34, Planetary Nebulae, p. 77). Hummer and Seaton (1964, M.N.R.A.S. 127, 217) effectively supposed that these photons are absorbed by H° in the central (He++) zone, whereas detailed line transfer calculations (Weymann and Williams, 1969, Ap. J. 157, 1201; Harrington, 1972, Ap. J. 176, 127) suggest that a large fraction of the photons escapes from the central zone. We consider the effects of the absorption of these photons on the ionization and thermal structure of the outer (He+, H+) zone of a nebula which is optically thick in the HI Lyman continuum. (Paper will appear in Astronomy and Astrophysics.)
On the Physical Differences Between the Planetary Nebulae of the Galactic Centre Group and the Planetaries of the General Galactic Field
Authors: Kostyakova E.B.
Published: June 2019

The mean physical parameters were estimated for the planetary nebulae of the two groups, regarded as a whole: planetaries of a general Galactic field (GGF), and those, belonging to a large group seen in the Galactic centre direction (CG).
The Uniformity of Chemical Composition of Galactic Planetary Nebulae
Authors: Barker Timothy
Published: June 2019

The relative abundances of H, He, Ne, O, and N have been determined in thirty planetary nebulae of widely-differing kinematical properties. Helium abundances are found to be affected by incomplete ionization of He, an effect that is strongly correlated with the abundance of S+. The He and N abundances appear to be positively-correlated, suggesting that nebular material has been contaminated through mixing with CNO-processed material. There is some evidence for a radial galactic abundance gradient in He, N, and possibly O and Ne; abundances increase toward the galactic center. This gradient is evident only from the nebulae that appear to be moving in circular orbits. All nebulae (except the previously studied planetary in the galactic halo and the one in the globular cluster M 15) have nearly the same abundances of O and Ne as galactic HII regions and the sun, and there is little correlation between these abundances and the kinematical properties of the planetaries. Apparently either Ne and O are not representative of the true heavy metal abundance, or the vast majority of planetaries belong to a metal-rich population. The latter possibility seems more likely in view of recent observations of the S++ abundances of nineteen of the nebulae, which show them to have generally solar S abundances. (Paper will appear in The Astrophysical Journal.)
The field luminosity function and nearby groups of galaxies
Authors: Huchra John
Published: June 2019

We have assembled a catalog of radial velocities and magnitudes on a homogeneous system (the corrected Harvard, B(o) magnitudes of de Vaucouleurs) for over 4000 galaxies. Using this catalog, we have compiled a magnitude limited sample of ~ 1000 galaxies with nearly complete radial velocity data. the magnitude limit is 13.0 and the galaxies are primarily from the Shapley-Ames catalog plus a few low and high surface brightness objects properly included in a magnitude limited sample. My colleagues, M. Davis, M. Geller and I are presently analyzing the dynamical properties of this sample. I would like to briefly describe a new determination of the field luminosity function and density plus our initial experiments with the use of a redshift catalog to select groups of galaxies.
Search for Primordial Perturbations of the Universe: Observations with Ratan-600 Radio Telescope
Authors: Parijskij Y. N.
Published: June 2019

All kinds of primeval perturbations of the Universe should result in fluctuations of the microwave background radio emission. Here we report our latest upper limits to these fluctuations on scales 5′ to 3°. Using the new 600-m Soviet Radio Telescope we obtained a mean temperature profile of the region from 08h to 15h in R.A., centred at the declination of the Coma Cluster. 20 good records of this region were used in the final reduction of the data. After “normalization” of these data by filtering out low-frequency atmospheric noise and “bursts” which exceed the 4σ level we calculated an upper limit to the fluctuations of the microwave background radiation.
Constraints on the mean density of the Universe which follow from the theories of adiabatic and whirl perturbations
Authors: Kurskov A. A. , Ozernoy L. M.
Published: June 2019

The aim of this communication is to investigate what constraints to the cosmological parameter Ω = 2qO can be obtained if one assumes that primaeval whirl motions or adiabatic density perturbations with an appropriate initial spectrum were responsible for the formation of large scale structure in the Universe. These constraints are readily obtained from the two conditions: (i) an upper limit to small scale temperature fluctuations of the microwave background radiation, and (ii) the requirement that the primaeval perturbations should be large enough in order to produce observed structures.
The Cooler Supergiants (A to M): Crucial Signposts in the Lifecycles of Massive Stars
Authors: Humphreys Roberta M.
Published: June 2019

The intermediate and late-type supergiants are the visually brightest stars. They are among the first stellar objects observed in other galaxies and provide our first clues to the conditions of massive star evolution in galaxies of different types. They are not as massive as the hottest and most luminous stars in the upper left of the HR diagram. Nevertheless, these somewhat lower mass stars (≈20−50 M⊙) with relatively cool temperatures play a major role in our efforts to understand massive star evolution. These supergiants are usually considered to be post hydrogen burning stars, and their relative numbers in the HR diagram provide essential comparisons with models for the later stages of massive star evolution. Most importantly, the most luminous cooler supergiants define the stability limit for massive stars in the HR diagram.
O-Star Winds: Is Rotation Important?
Authors: Prinja Raman , Howarth Ian
Published: June 2019

The inclusion of rotation as an ingredient in radiation pressure driven stellar wind models is a nontrivial undertaking. Those bold enough to attempt an investigation of its likely importance include Castor (1979), Abbott (1980), and Marlborough & Zamir (1984), whose work shows that the critical point is expected to move away from the stellar surface with increasing rotation. Observationally, the surface mass flux is predicted to be insensitive to rotation, but the wind acceleration is expected to be less than in a nonrotating star and the terminal velocity smaller.
New Results on Eta Carinae. Evidence for an Asymmetric, Inhomogeneous Wind
Authors: Viotti R. , Rossi L. , Altamore A. , Rossi C. , Cassatella A.
Published: June 2019

The very peculiar object Eta Car is one of the best laboratory for the study of those physical processes - such as mass loss, superionization, dust condensation, wind interaction with the i.s. medium - that presently are of great astrophysical interest, especially for the study of the most luminous stars. For its light history and high luminosity Eta Car may also be considered as the galactic counterpart of the Hubble-Sandage variables. Eta Car is one of the rare astrophysical objects with evidence of dust condensation from ejected stellar matter (Andriesse et al. 78) On the other side the star is also producing a strong, hard X-ray flux (Chlebowski et al. 1984), and the problem is whether there is any physical reason to have these two quite different processes in the same stellar environment. In any case rather extreme physical conditions are required which cannot be verified in a uniformly, spherically symmetric atmospheric enevelope. Andriesse et al. in fact suggested the presence of strong inhomogeneities, such as filaments, possibly related to the presence of a strong magnetic field. This may also explain the X-ray emission. In the following we shall present new optical and UV observations of Eta Car and its small nebula with the aim of clearfying the physical nature of its wind.
The Distance Modulus of LMC
Authors: Chiosi Cesare , Pigatto Luisa
Published: June 2019

Deep CCD photometry of the star clusters NGC2162 and NGC2190 in LMC presented by Schommer et al. (1984) is used togheter with new evolutionary models computed by Bertelli et al. (1985a) which take into account overshooting from convective cores, to derive the clusters ages and the distance modulus of LMC. A preliminary analysis of the two clusters indicates that NGC 2162 and NGC 2190 belong to the same class of clusters discussed by Barbaro and Pigatto (1984). In fact, for the turn-off mass estimated by means of classical models (<2.2m⊙) these clusters should possess an extended red giant branch and a bimodal distribution of red stars (cifr. Fig.2). On the contrary they show a clump of red stars. This means that ages and other properties derived from classical models for this range of masses, may not correspond to reality. With the new models, stars of mass as low as 1.6 m⊙, ignite helium in non degenerate conditions, avoid the long lived RG phase, and burn helium as more massive stars. As consequence of it, a clump of red giants is expected. In Fig.1, we show new isochrones (Bertelli et al. 1985b) derived from models with overshooting, overlaid to the CM diagram of NGC 2162. Theoretical luminosities and Teff's are converted into Mv:(B-V)o plane by means of Teff:(B-V):BC scales based on models atmospheres collected from several authors (Chiosi, 1985). At any given age, the new isochrones run brighter than those of Ciardullo and Demarque (1977). By means of the luminosity function, a method more objective (Paczsynski, 1984) than the standard one of ZAMS and/or isochrone fitting, with a reddening of E(B-V)=0.06 and chemical composition X=0.700 and Z=0.02, we find ages of 1 109yr and a true distance modulus of (m-M)O=18.6 instead of 18.2±0.2 mag given by Schommer et al.(1984). Fig.2 shows the theoretical luminosity function at age 1 109yr, (age preliminarly assigned to the clusters by isochrone fitting) for main sequence and red giant stars obtained with Salpeter's IMF (top panel), compares it with the correspondent one of Ciardullo and Demarque(1977), and finally shows the observational LF we derive from stars counts(bottom panel) for NGC 2162. By imposing coincidence between theoretical and observational LF's at the side of main sequence fall-off and rising of the red giant clump, we derive the distance modulus (m-M)O=18.6. In conclusions, models with overshooting not only interpret the morphology of this class of clusters, but assigne LMC a distance modulus in agreement with other independent determinations (Walker, 1984; Visvanathan, 1985).
NGC 2070 and NGC 3603
Authors: Chu You-Hua , Seitzer Patrick , Walborn Nolan
Published: June 2019

Giant H II regions are usually so distant that only the integrated properties of their stellar contents can be studied. However, the nearby giant H II regions 30 Doradus in the Large Magellanic Cloud and NGC 3603 in the Galaxy offer a rare opportunity for a spatially resolved study of their central stellar associations — NGC 2070 and NGC 3603. We have obtained 4m prime focus plates with interference filters centered on the He II 4686 line (Δλ = 65 A) and the adjacent blue continuum at 4765 A (Δλ = 70 A) to identify the Wolf-Rayet (WR) stars in their cores. We have also obtained CCD images in UBVRI for NGC 2070, and BVRI for NGC 3603 to determine their color-magnitude diagrams and luminosity functions. Since the WR stars in the core of 30 Dor have been reported by Chu, Cassinelli, and Wolfire (1984) and Moffat, Seggewiss, and Shara (1985), and the CCD photometry of NGC 2070 and 3603 is still preliminary, we will discuss in these proceedings only the WR stars resolved in the core of NGC 3603.
Kinematics of Nearby FV Stars
Authors: Shuter W.L.H. , Stocker W. N.
Published: June 2019

The line-of-sight velocity field has been determined for all 80 FV stars within 15 degrees of the North Galactic Pole (NGP) with measured and constant velocities, and measured distances, from the catalogs of Hill et al. (1976, 1982). These data are a subset of the data used in a determination of Kz by Bahcall (1984). Procedures were as described by Goulet and Shuter (1984). The velocity field is depicted in Figure 1, and the magnitude of the velocity residuals is plotted in Figure 2.
Distribution of Dark Matter in Polar Ring Galaxies
Authors: Whitmore Bradley C. , McElroy Douglas B. , Schweizer François , Rubin Vera C.
Published: June 2019

The discovery of SO galaxies with polar rings makes it possible to directly measure the gravitational potential of a galaxy in three dimensions. Schweizer, Whitmore and Rubin (1983) find a spherical potential in the case of A0136-0801. We have observed three more polar ring galaxies using the 4 meter telescope at CTIO. The following table summarizes the results for these three systems as well as A0136-0801, and figure 1 shows an example of the data.
A four star photometer for use on small telescopes
Authors: Caton D. B. , Pollock J. T.
Published: June 2019

An automated photoelectric four-star photometer has been designed for use on the 46-cm reflector at Appalachian State University's Dark Sky Observatory. The system will be composed of integrated detector-amplifiers, stepper-motor controlled x-y stages, and automatic counters.
Stellar photometry with small telescopes
Authors: Twarog B. A.
Published: June 2019

The dominant trend within stellar photometry in recent years has been an increase in the number of intermediate and narrow-band photometric observations, particularly with small telescopes. Recent examples illustrating the scope and emphasis of such programs are reviewed. It is concluded that with continuing improvement in detector technology and telescope automation, small telescope photometry will grow in importance.
A program of new accurate photometry for bright stars
Authors: Crawford David L.
Published: June 2019

A new program of accurate photoelectric photometry for the brightest stars is getting underway, using the excellent small telescopes and talents of amateur astronomers.
Standard stars for comet photometry
Authors: Osborn Wayne , Birch Peter , Feierberg Michael
Published: June 2019

Photoelectric photometry of comets is a feasible and worthwhile research program for small telescopes. Nine filters designed to isolate selected emission features and continuum regions in cometary spectra have been adopted by the IAU as those recommended for comet photometry. Magnitudes of standard stars for the IAU filter system have been derived. The results have been compared with previous observations and transformations to place all observations on a common system obtained.
The RS CVn project at Capilla Peak Observatory
Authors: Zeilik M.
Published: June 2019

The 61-cm telescope at the Capilla Peak Observatory of the University of New Mexico was used extensively from 1979 to 1982 for UBVR observations of selected RS CVn stars. (See Elston and Zeilik, 1982, for details of the system.) Complete coverage was obtained from most of the short-period systems (Hall, 1976)-RT and CG Cyg, XY Uma (the most active of these systems), UV Psc and ER Vul-with a precision of 0.01 mag or better for each datum. Our early experiences showed that these stars had rapid intrinsic variations (within a month).