bluuebunny/crossref_metadata_2025 huggingface dataset:
The Remarkable Rotational Braking of G5 Giants
Authors: Gray David F.
Published: June 2019

The strong rotational braking seen in the G5 III stage of evolution may be the key to understanding how stellar dynamos work.

We are all familiar with the leisurely spin-down seen in cool main-sequence stars like our Sun. The time scales here are ∼ 109 years and the accepted cause is the loss of high angular momentum mass in the form of stellar winds interacting with the stellar magnetic field. The magnetic field is believed to result from the interaction of envelope convection with the rotation of the star through a dynamo mechanism. Our understanding of how a dynamo actually operates, how that operation depends on the driving forces of rotation and convection, what kind of stochastic and secular time variations are to be expected, remains fragmentary even though many inventive minds have contributed. One reason for slow progress is simply that the Sun is almost the only example of a stellar dynamo we have had. But nature has given us another, much more powerful dynamo in the G5 giants, it just took us a little longer to discover it.
Observational Needs for Progress in Solar/Stellar Magnetic Activity: Overview
Authors: Noyes Robert W.
Published: June 2019

Recent observational and theoretical findings have clarified the physical mechanisms which underlie magnetic activity production in stars, and point the way naturally to a number of new or more crisply defined questions, whose answers can lead to major progress in the near future. Concerning observational programs, a guiding principle has been evident throughout this symposium: We should rely heavily on the Sun for understanding the detailed physics of magnetic activity and its generation, while at the same time we study analogous stellar phenomena for comparison with the Sun, and for new insights and extension to different regions. I list below some broad observational areas in which conditions seem ripe for important progress in understanding solar and stellar magnetic activity, leaving to other summarizers the discussion of particular observational programs.
This Volume is dedicated to the Memory of Bart Jan Bok
Authors: van den Bergh Sidney , de Boer Klaas S.
Published: June 2019

The evolutionary history of the Magellanic Clouds has been very different from that of the Galaxy. As a result we presently observe major differences between both the stellar content and the cluster populations in the Galaxy and the Clouds.
A BVRI Photometric Study of Star Clusters in the Bok Region of the LMC
Authors: Alcaino Gonzalo , Liller William
Published: June 2019

The large number of star clusters in the Large Magellanic Cloud provides us with an excellent opportunity to understand well this neighboring galaxy. The large variety of integrated cluster colors present suggests a wide range in evolutionary stages, and several studies have established vague relationships between their location in the LMC and properties including color, total luminosity and metallicity.
A BV Photometric Study of Star Clusters in Two Selected Regions of the SMC
Authors: Alcaino Gonzalo , Liller William
Published: June 2019

We are deriving BV color-magnitude diagrams of star clusters in two selected regions in the SMC. These zones, characterized by the presence of a high density of star clusters, are centered at the 1981 coordinates for region 1: (RA: 1h, Dec −73°08′), and for region 2: (RA: 1h 10m.33, Dec −73°00′). See Figure 1 for their identification relative to the SMC.
Comparison of Theoretical and Observed Indices for Three Photoelectric Photometric Systems
Authors: Rufener F. , Maeder A.
Published: June 2019

A comparison of the theoretical and observed indices has been made for the UBV, u v b y and the Geneva's UBVB1B2V1G systems. In the actual state of the photometric calibrations, coincidence between theoretical and observed indices better than are probably not significant.
Determination of the Apparent V Magnitudes
Authors: Rufener F. , Maeder A.
Published: June 2019

V photoelectric magnitudes are determined on an independent basis. Correlation with V sequence of the UBV system confirms the coincidence of the two definitions. Comparisons with the Catalogue of Bright Stars revealed that more than 40% of BS stars have an apparent V magnitude with a probable error of .
The Precision of J2000.0 Radio Source Positions from Mark III VLBI
Authors: Ma C.
Published: June 2019

A celestial coordinate frame defined by extragalactic radio sources has been developed from Mark III VLBI data. 33 000 delay and delay rate pairs acquired between August 1979 and December 1982 have been analyzed to give positions for 82 radio sources. Standard J2000.0 astronomical models were applied. 90% of the formal errors for arc lengths between sources are less than Arc lengths estimated from separate one-year data sets are consistent at the to level.
Trigonometric Parallaxes Obtained with the UK Schmidt Telescope
Authors: Murray C A , Corben P M , Argyle R W
Published: June 2019

In continuation of a long term programme of measurement of parallaxes and proper motions in the South Galactic Cap from plates taken with the UK Schmidt Telescope and measured in GALAXY at RGO, data for some 800 red stars brighter than B = 17.5 have been derived from two independent plate series. The parallaxes obtained from unfiltered IIaO plates show a large systematic error depending on magnitude compared with those obtained from IIaD plates with GG 495 filter. After correction, the combined trigonometric parallaxes show very satisfactory agreement with photometric parallaxes, and the average r.m.s. error of a combined parallax is found to be about ±0″.012 both from internal and external evidence.
Microarcsecond Astrometric Interferometry
Authors: Reasenberg Robert D.
Published: June 2019

A small astrometric optical interferometer, Mini-POINTS, which would fit fully assembled in about one-third of the Shuttle bay, could measure the angle between stars about 90° apart. For 10th magnitude stars, an observation time of about 20 minutes would yield a measurement uncertainty of 5 microarcseconds. When compared to an astrometric telescope of comparable size which observes the same target for the same period of time, such an interferometer would achieve a greater accuracy by two to three orders of magnitude. Five design criteria lead to an instrument that achieves high precision by employing photon statistics for fringe splitting and achieves high accuracy by means of continuous internal metrology with laser interferometers. The high throughput of Mini-POINTS permits a mission design that addresses a wide variety of scientific questions.
Present Status and Future Plans for the Two Color Astrometric Interferometer Project
Authors: Shao M. , Colavita M. , Staelin D. , Simon R. , Johnston K.
Published: June 2019

A 3-meter two telescope stellar interferometer has been used to observe fringes for the past year in order to study the feasibility of using long baseline interferometers for astrometry. We have demonstrated that two color fringe measurements are capable of significantly reducing the astrometric error due to atmospheric turbulence. Currently, we are investigating the thermal and mechanical sources of error in the instrument. The results of our study will be incorporated into the design of the 20 meter astrometric interferometer which will be built in the next 1–2 years. The key to the 20-meter interferometer is the laser system which we expect to monitor all the mechanical and thermal imperfections relevant to astrometry at the 10−3 to 10−4 arc sec level. A slight modification of this system could be used in a space based interferometer for 1 to 10 microarcsecond astrometry of faint objects.
Moving-Image Astrometry With the Multi-Anode Microchannel Array (MAMA) Detector
Authors: Scargle Jeffrey D.
Published: June 2019

Consider the possible astrometric use of the following concept: If the image of a field of stars is moved past a high-speed detector array at a precisely known velocity, relative positions can be determined by measuring time intervals. Attractive features of this approach are: times can be measured very accurately with photoelectric detectors; a relatively large area of the sky may be swept for reference stars; the images are measured essentially on-axis; and seeing effects can be partially frozen out. The only available detector with spatial and temporal resolution and stability adequate for this technique is the MAMA. A rudimentary observational test with this detector has yielded promising results. Further observations are planned to determine whether milliarcsecond accuracy can be obtained.
Design for a Large Transit Circle with Reflecting Optics
Authors: Hu Ningsheng
Published: June 2019

This paper describes a conceptual design for an automatic transit circle with Ritchey-Chretien Cassegrain type optics of 40 cm aperture. The instrument takes reversal observation both in the meridian and in the prime vertical. Methods of adopting active optics to achieve a stable boresight of the reflecting telescope and of automatically reversing and leveling the instrument are presented. The instrument can also be used in a theodolite mode.
The Refurbished Six-Inch Transit Circle
Authors: Klock B. L.
Published: June 2019

The U.S. Naval Observatory (USNO) six-inch transit circle at Washington underwent extensive refurbishment during the interval between October 1982 and May 1983. Major items refurbished on the instrument included the micrometer, the clamp and slow motion arm, the screen system, and a circle. Support instrumentation refurbished included a new digital motor drive system, a new digital micrometer display system, and new environmental measuring systems. Finally, the telescope was completely repainted and the pavilion was extensively renovated.
A New Method for Zenith Distance Determination in Meridian Observations
Authors: Miyamoto M. , Yoshizawa M.
Published: June 2019

In meridian observations, the main error sources of the declination observation reside in determination of the atmospheric refraction, the flexure of the telescope and the division errors of the graduated circle. In order to obtain higher accuracy in the declination observation, besides a full automation device, the photoelectric meridian circle at Tokyo Astronomical Observatory (Tokyo PMC) is equipped with photoelectric devices for circle reading and a zenith mirror in addition to the conventional mercury horizon. We report here on a preliminary determination of the horizontal and vertical flexures, and of the division errors of the glass circle.
Cumulene Carbenes in Space and in the Laboratory
Authors: Vrtilek J. M. , Gottlieb C. A. , Killian T. C. , Thaddeus P. , Cernicharo J. , Guélin M. , Paubert G.
Published: June 2019

Astronomical searches for H2CCC and H2CCCC, based on frequencies from our laboratory identifications, have resulted in detections toward TMC-1 and IRC+10216. These new interstellar species are possibly the first of a new family of highly polar carbon chains; they are only the second and third carbenes (carbon molecules with two nonbonded electrons) known in space.
Theoretical Modelling of the Infrared Fluorescence by Interstellar Polycyclic Aromatic Hydrocarbons
Authors: Schutte W. A. , Tielens A. G. G. M. , Allamandola L. J.
Published: June 2019

We modelled the IR emission of interstellar PAHs. Substantial differences between the IR properties of interstellar and laboratory PAHs are found, possibly resulting from ionization. The various IR features being dominated by distinctly different size PAHs, their observed relative intensities are sensitive indicators of the size distribution. A number of applications of our model related to future ISO and SIRTF IR data are pointed out.
Abundance of CH+ in Translucent Molecular Clouds: Problems for Shock Models?
Authors: Gredel R. , Van Dishoeck E.F. , Black J.H.
Published: June 2019

The large abundance of CH+ in diffuse clouds has been a mystery for more than 50 years (Dalgarno 1976). Many different explanations have been proposed, but only (shock) models with a substantial column of warm gas appear capable of approaching the observed column densities (Elitzur and Watson 1978). In these models, CH+ is formed in the warm postshock gas through the reaction C+ + H2 → CH+ + H, which is endoergic by 4650 K. Although the most sophisticated MHD shock models are consistent with various observational aspects of CH+, they require substantial “fine-tuning” of the parameters (Draine and Katz 1986; Hartquist et al. 1990). In addition, they predict a shift in velocity between CH+ and other molecules found in the cold quiescent gas, which is not observed in recent data (e.g. Crawford 1989). In order to test further the shock models, we have searched for CH+ in a number of translucent clouds (AV ≍ 1-5 mag), which have H2 column densities that are up to an order of magnitude larger than the clouds studied so far (cf. Souza 1979). Observations of the chemically related molecules CH, C2, CN and CO have been obtained as well.
Molecular Line Studies of Dense Core Motions
Authors: Wu Yuefang
Published: June 2019

Molecular lines have revealed various supporting motions in dense cores. Line widths and emission region sizes of NH3 and CS in the same kind of cores or of the same line in cores with or without sources are different and can not be explained with the line width- size relationship. Outflows in dense cores show rich characteristics which can account for the NH3 emission difference between the two kinds of the cores; CS emission is consistent with the chemical effects in shocked regions. Rotation exists in both kinds of cores and may be related to the observed polarities and collimations of outflows.
H2O Maser Pumping by Shock Waves
Authors: Lepine Jacques R.D. , Heske Astrid
Published: June 2019

We discuss a simple H2O maser pumping mechanism in which the population inversion of the masing levels takes place during the quick cooling of the gas behind a shock wave. The population of the rotational energy levels in the initial hot state and final cool state of the molecular gas, and the decay paths between levels are analysed to calculate the average number of 22 GHz photons emitted per H2O molecule in the cooling process.
Methanol Masers in W3(OH)
Authors: Zeng Qin
Published: June 2019

The formation conditions of the methanol masers in W3(OH) are studied separately. The lower limits of the densities of the A- and E-type maser regions are 105 and 106 cm−3. The A-type maser requires a stronger excitation from HII region, than the E-type maser. The relative abundance of methanol to molecular hydrogen is more than 5×10−5. The calculation indicates that there are maser series (J0-(J+1)-1) E, (J1-(J+1)0) E J=1,2 and (J2-(J+1)1) A+ J=7,8,9 in W3(OH).
Chemical Composition of a Southern Planetary Nebulae Sample
Authors: De Freitas Pacheco J.A. , Costa R.D.D.
Published: June 2019

We report the results of our analysis of a well observed sample of southern planetary nebulae. The average S/O and Ar/O ratios are comparable to the solar value and to those observed in galactic H II regions. The He abundance correlates with the N/O ratio, confirming the trend found by previous studies, indicating the surface contamination of the progenitors by dredge-up episodes.
G305.8 - 0.2: A Young Object with a Dust and Gas Envelope
Authors: Vilas Boas J.W.S. , Scalise E. , Sanzovo G.G. , Mendes Pacheco G. , Gómez Balboa A.M.
Published: June 2019

The H2O maser source in G305.8 - 0.2 was first detected by Haynes et al. (1984). Inspection of the Southern Hemisphere radio surveys did not show any strong compact HII region or water maser placed nearby this source. The IRAS point source catalog (2.0) shows a strong source in the direction of the maser. We analysed the temporal variation and line profile of the H2O maser emission and discussed the nature of its associated IRAS source. These source characteristics seem compatible with the hypothesis that the maser is associated with a protostellar disk around an early-type star of spectral type 07 to 09 surrounded by a spherical shell of gas and dust.
Radio Interferometric Observations of Cometary Molecules
Authors: Palmer Patrick , E. Snyder Lewis , de Pater Imke
Published: June 2019

A useful method for extracting cometary signals is demonstrated using VLA observations of Comet Brorsen-Metcalf (1989o).
A Model of P/Tempel 2 With Dust and Detailed Chemistry
Authors: Huebner W.F. , Boice D.C. , Konno I. , Singh P.D.
Published: June 2019

We apply our fluid dynamic model with chemical kinetics of dusty comet comae to P/Tempel 2. A brief summary of results concerning gas/dust dynamics and chemistry is given.
Summary
Authors: Williams D A
Published: June 2019

The quantity of scientific work in the area of astrochemistry is now enormous, and this meeting - in attempting to cover most of the aspects of our subject - has had problems in coping with it due to difficulty of reviewing very active, broad areas in a limited time. At this meeting we have had almost 40 hours of formal and informal discussion, and about 45 oral presentations at which I estimate that about 1500 transparencies and slides have been projected for our enlightenment. About 100 posters have been presented in three sessions. The posters were uniformly of a high standard and generated a great deal of interest and discussion. I think the prominence given in the programme to the posters has been particularly successful. The range of activity, and the enthusiasm with which it is pursued, demonstrate that astrochemistry is in a vigorous state. It has its own intrinsic interest, and in its present maturity is now making substantial contributions to understanding in astronomy.
The Locations of Secular Resonances and the Evolution of Small Solar System Bodies
Authors: Froeschle Ch , Farinella P. , Froeschle C. , Knežević Z. , Milani A.
Published: June 2019

Generalizing the secular perturbation theory of Milani and Knežević (1990), we have determined in the a — e — I proper elements space the locations of the secular resonances between the precession rates of the longitudes of perihelion and node of a small body and the corresponding eigenfrequencies of the secular perturbations of the four outer planets. We discuss some implications of the results for the dynamical evolution of small solar system bodies. In particular, our findings include: (i) the fact that the g = g6 resonance in the inner asteroid belt lies closer than previously assumed to the Flora region, providing a plausible dynamical route to inject asteroid fragments into planet-crossing orbits; (ii) the possible presence of some low-inclination “stable islands” between the orbits of the outer planets; (iii) the fact that none of the secular resonances considered in this work exists for semimajor axes > 50 AU, so that these resonances do not provide a mechanism for transporting inwards possible Kuiper–belt comets.
Application of Wisdom's Perturbative Method to the 5:2 and 7:3 Resonances
Authors: Yokoyama Tadashi , Balthazar José M.
Published: June 2019

Wisdom's perturbative method is applied to the 5:2 and 7:3 resonances. Some comparisons with Yoshikawa's model are performed: for values of eccentricity up to about 0.3-0.4, agreement exists and it is better for 5:2 resonance. A clear difference between the cases 5:2 and 7:3 is observed: the former one, like in the case 3:1, can show significant variations of eccentricity, even starting from very small values, close to zero, while the latter seems to undergo such variations, but with initial eccentricity not less than a value near 0.1.
Corotations in Some Higher-Order Resonances
Authors: Ferraz-Mello S. , Tsuchida M. , Klafke J.C.
Published: June 2019

Some results concerning the resonances 3:1, 4:1 and 5: 2 are given and compared to results published by other authors.
The Effect of Non-Stationary Action on the Motion of Particles in Protoplanetary Nebulae
Authors: Baranov A.S.
Published: June 2019

Dynamical evolution of a plane system of non-interacting particles, which are in a certain smoothed-out regular field, is of a certain interest in a number astronomical applications. Among them are the plane subsystems of the spiral galaxies, the rings of the giant planets and protoplanetary nebulae. The problem of determining the stationary state of these systems has been studied enough [1]. But one seldom comes across studies concerning with the reaction of the non-stationary field.
New Methods for Long-Time Numerical Integration of Planetary Orbits
Authors: Kinoshita Hiroshi , Nakai Hiroshi
Published: June 2019

When planetary orbits are numerically integrated for a long time by conventional integrators, the most serious problem is secular errors in the energy and the angular momentum of the planetary system due to discretization (truncation) errors. The secular errors in the energy and the angular momentum mean that the semi-major axes, the eccentricities, and the inclinations of planetary orbits have a secular error which grows linearly with time. Recently symplectic integrators and linear symmetric multistep integrators are found not to produce the secular errors in the energy and the angular momentum due to the discretization errors. Here we describe briefly both methods and discuss favorable properties of these integrators for a long-term integration of planetary orbits.
Radar Mapping of the Moon at 162 Mhz
Authors: Ponsonby J. E. B. , Morison I. , Birks A. R. , Landon J. K.
Published: June 2019

The result of Lunar radar mapping observations are presented, which were made at Jodrell Bank in January and February 1970 at 162.4 MHz in the depolarized return. The Maps show that most of the depolarized return comes from the highland regions. No significant return has been detected from the Maria. Certain isolated features are particularly prominent, notably the craters Tycho and Theophilus which appear almost equally intense, also the areas around Werner and Fourier. Various other features can be identified with less reliability. These results are discussed in qualitative terms.
Electron Microscopic Studies of Some Lunar Minerals
Authors: Champness P. E. , Lorimer G. W.
Published: June 2019

Ion-thinned samples of rock 12052 have been examined in the electron microscope at 100 kV. This rock contains numerous phenocrysts of pyroxene, Ca1 – P (Mg, Fe)1 + P Si2O6, and a few rounded olivine crystals (Mg, Fe)2 SiO4 set in a finer-grained groundmass of pyroxene, plagioclase (Na, Ca) (Al, Si)4O8, ilmenite, FeTiO3 and other minor minerals (Champness et al., 1971). The cores of the pyroxene phenocrysts consist of a calcium-poor pyroxene, pigeonite, with an epitaxially grown rim of a calcium-rich pyroxene, augite. Both the pigeonite and augite are zoned, and indication of non-equilibrium crystallisation (Bence et al., 1970).

The outer parts of the pigeonite cores of the phenocrysts show very finescale composition modulations on (001) (major) and (100) (minor) (Figure 1). This texture is interpreted as exsolution by a spinodal mechanism (Cahn, 1968).

The augite rim of the phenocryst exhibits a coarse exsolution of pigeonite on (001) on which is superimposed fine-scale composition modulations on (001) and (100) (Figure 2).

The two-stage exsolution process indicates that the cooling rate of the pyroxene increased suddenly, possibly when the magma was extruded on the Moon's surface.

Antiphase domains produced during the polymorphic transition from space group C2/c to P21/c have been found in all primary and precipitated pigeonites (Figure 3). This confirms Morimoto and Tokonami's (1969) suggestion that all clino-pyroxenes have the C2/c space group at high temperatures.

Cristobalite, a high-temperature polymorph of silica, occurs as very small grains in the groundmass. It contains numerous microtwins on {100} planes produced during the β→α polymorphic transition which occurs at 268°C (Figure 4a). Diffraction patterns show extensive diffuse streaks in various directions (Figure 4b) which correspond to intersections of planes in reciprocal space with the Ewald Sphere. These diffuse planes originate from the cooperative thermal vibration of Si-O chains parallel to {100} and {111}.
A Possible Mechanism of the Generating of the Unusually Long Lunar Seismic Oscillations
Authors: Passechnik I. P. , Sultanov D. D.
Published: June 2019

One of the possible reasons of the long duration of lunar seismograms are multiple reflections in the upper part of lunar cross-section, similar to those generating under Earth conditions. While registration of seismic oscillations in a region with stratified low-velocity sediment rocks of 6–7 km thickness the authors observed long seismic low-decaying oscillations. The observed decay was about 40 db during 30 min.

The long duration records are obtained only on the distances where the intense overcritical reflections exist from the M-boundary situated at a depth of 50 km.

These waves generated numerous multiple reflections, longitudinal, shear and converted waves in the upper part of the cross-section. These body waves are responsible for the generation of the surface waves, recorded in the subsequent parts of the seismograms. Periods of body waves are about 1–1.5 s., those of surface waves – about 1.5–3 s.

Extrapolating similar mechanism of the wave generation to lunar media, one should assume the presence of a layered upper part of the cross-section and the possibility of the sufficiently intense wave incidence on its lower boundary.

It is possible if either reflecting boundaries or a vertical velocity gradient are present in the underlying media. The first variant is accompanied with overcritical reflections, the second one – with intense refracted waves.
Geologic Interpretation of the Study of Lunar Rocks
Authors: Kopecký Lubomír
Published: June 2019

The hypothesis on an internal origin of lunar rocks of gabbroic type is supported by experimental petrologic data obtained by the author. The temperature interval of their crystallization from a dry silicate melt is given.

Lunar gabbroic rocks of the Tranquillity Base are compared with paleobasalts of north-eastern Bohemia, eucrites and associated rocks of the British Isles and meteoritic eucrites of poikilophitic texture.

The metasomatic origin of lunar anorthosites displaying a mosaic texture in deeper parts of the volcanic apparatus is postulated.

An analogy is thought to exist between the Tertiary volcanic areas of Mull, Ardnamurchan and Rum in Scotland and the Ptolemaeus, Alphonsus and Arzachel regions of the Moon in the overall tectonic structure and the development of tectono-volcanic cirques. By analogy the possibility of the presence of more basic rocks in the rim and on the floor of the Moon subsidence calderas and of more acidic rocks of anorthositic to trachyandesitic chemistry in the central peak is presumed.

The mode of origin of double-craters of Cyrillus-Theophilus type is suggested to be similar to the origin of two consecutive volcanic rings of Mull.

The ring- and radial complexes of wrinkle ridges of Lamont type are compared with cone sheets and radial dykes of the central type tectono-volcanic complex of Mull.
Lunar Magnetic Field Measurements, Electrical Conductivity Calculations and Thermal Profile Inferences
Authors: Colburn D. S.
Published: June 2019

Steady magnetic field measurements of magnitude 30 to 100 γ on the lunar surface impose problems of interpretation when coupled with the non-detectability of a lunar field at 0.4 lunar radius altitude and the limb induced perturbations of the solar wind reported by Mihalov et al. at the Explorer orbit. The lunar time varying magnetic field clearly indicates the presence of eddy currents in the lunar interior and allows calculation of an electrical conductivity profile. The problem is complicated by the day-night asymmetry of the Moon's electromagnetic environment, the possible presence of the TM mode and the variable wave directions of the driving function. The electrical conductivity is calculated to be low near the surface, rising to a peak of 6 × 10−3Ω−1 m−1 at 250 km, dropping steeply inwards to a value of about 10−5Ω−1 m−1, and then rising toward the interior. A transition at 250 km depth from a high conductivity to a low conductivity material is inferred, suggesting an olivine-like core at approximately 800 °C, although other models are possible.
Thermal Gradients in the Outer Lunar Layers
Authors: Bastin J. A. , Pandya S. J. , Upson D. A.
Published: June 2019

During the next Apollo mission Apollo 15, it is planned to fix thermocouples at various depths up to 3 m below the lunar surface. It seems likely that the resulting temperature measurements will show a positive temperature differential with depth resulting from a net outward heat flux. It is the purpose of this paper to examine experiments already carried out which indicate a temperature gradient. Since the thermal flux is of direct importance in fundamental problems of lunar origin and the nature of the lunar interior, the relation between this quantity and the temperature gradient will be examined.
Summary-Introduction
Authors: Böhm-Vitense E.
Published: June 2019

Since there is the excellent summary on stellar convection given by J.-C. Pecker at the Liège symposium on stellar evolution in 1959, where he gives a complete account of the existing literature, I shall in this summary not try to do justice to the history of stellar convection research nor shall I try to mention all the existing papers even if they are quite important. I shall rather attempt to give an objective picture of the present state of affairs in order to be able to discuss our problems with the aerodynamicists. I shall cite only those papers that have been explicitly used for the results presented here. Additional references to literature may be found in the article by J.-C. Pecker.
Summary-Introduction: Similarity arguments for fully developed turbulence
Authors: Malkus W. V. R.
Published: June 2019

In the study of turbulent flows similarity arguments are used to explore the consequences of non-mechanistic assertions concerning the general behavior of the flow. For example, it is currently assumed that viscosity plays no role in the determination of the mean velocity profile of turbulent shearing flow far from a boundary. The consequences of this assumption are that the amplitude of the mean velocity will be determined by the momentum transported into such a region and that the velocity profile will be a solution to Euler's equations.
Second Summary-Introduction: Steady One-Dimensional Fluid-Magnetic Collisionless Shock Theory
Authors: Blank A. A. , Grad H.
Published: June 2019

Shock-waves represent one of the most important mechanisms for creating and heating a plasma. In classical non-dissipative gas dynamics, the formation of a shock is indicated by the progressive steepening of a finite-amplitude compressive wave front to the point where it becomes multivalued and consequently without physical meaning. This difficulty is avoided by the inclusion of dissipative effects, usually in the form of heat flow and viscosity. The dissipative mechanisms become more effective as the wave front steepens, and the result is a steady wave profile for which the non-linear and dissipative effects are counterbalanced. The scale length for the dissipative transition zone or wave profile is the mean-free-path; the actual thickness may range from one to several mean-free-paths, or even more for very weak shocks. Given the strength of the shock, the state on one side of the shock may be computed from the state on the other side directly from the laws of conservation of mass, momentum and energy (Hugoniot relations). Accordingly, the nature of the particular dissipative mechanism affects only the shape of the shock profile but not the end states.
The stellar population of the inner 200 parsecs
Authors: Rich R. Michael
Published: June 2019

The central 200 pc of the Galaxy is obscured by 5-30 visual magnitudes of extinction and therefore may be studied only in the infrared. The central parsec consists of a mostly red star cluster (IRS 16) and a cluster of ≈ 10 HeI Wolf-Rayet or Of-like stars; this cluster is the best evidence for star formation in this region. The central 5 pc has an extended giant branch (to Mbol/=−6) and long period variables. These stars are not extraordinarily bright; in the central 200 pc luminous asymptotic giant branch (AGB) stars (Mbol < −5) concentrate toward the nucleus in a distribution more flattened than the general light. Candidates for relatively young objects include a rapidly rotating population of high outflow velocity OH/IR stars. The AGB luminosity function in the central 200 pc resembles that recently found in M32 and M31 bulge fields. Depending on how one interprets the extended giant branch, the population may be intermediate age with some ongoing star formation, or mostly old and metal rich, with star formation confined to the nucleus.
Summary: achievements and open questions
Authors: Freeman K.C.
Published: June 2019

Without attempting to cover all of the topics discussed at this meeting, I plan to talk briefly about some of the major achievements and ideas that came up here, and then mention a few of the important open questions and some work that might be done to answer them.
Dynamics of the Galactic Bulge from gas motions
Authors: Gerhard Ortwin E. , Binney James
Published: June 2019

Observations of cold gas in the inner galactic disk show a clumpy, highly asymmetric distribution, with large non-circular velocities. Recent work has shown that the flow of gas in the inner few kpc is dominated by a rapidly rotating bar, with corotation at R ≃ 2.4 kpc and oriented at an angle of θincl = 16 ± 2° with the line-of-sight to the Galactic Center. From the kinematical model the gravitational potential in the inner Galaxy can be determined. Gas falls inwards through the bar's inner Lindblad resonance at a rate of ∼ 0.1M⊙/ yr; this suggests that in episodic star formation significant mass and angular momentum may be added to the inner bulge.
Preliminary results of the two micron galactic survey
Authors: Calbet X. , Mahoney T. , Hammersley P. , Garzón F. , Selby M.
Published: June 2019

We present the first results of the Two-Micron Galactic Survey (TMGS). The sources are concentrated on the Galactic plane, the width of the distribution increasing between 0° and 30° longitude. Several obscuration lanes are seen, showing that K-band absorption can be high and patchy.
The Bulge/Halo interface rotational kinematics from [Fe/H] = −3.0 to Solar
Authors: Harding Paul , Morrison Heather
Published: June 2019

Kinematics and abundances have been determined for a large sample of K giants in a field at ∼2 kpc from the center to study the relationship between the bulge and the halo. There are two different kinematic groups evident. The metal-poor stars have low rotation and high velocity dispersion, and so can be associated with the halo. The metal-richer stars have intermediate rotation. Our data suggest that the bulge and halo could be separate kinematical entities.
Microlensing towards the Galactic Bulge
Authors: Udalski Andrzej , Szymanski Michal , Kaluzny Janusz , Kubiak Marcin , Mateo Mario , Preston George , Krzeminski Wojciece , Paczynski Bohdan
Published: June 2019

We describe an ongoing survey to search for dark matter via lensing events of stars in the Galactic Bulge. The principal properties of the survey are described, and some preliminary results are shown for newly-discovered variables. We discuss some of the projects related to the study of the Galactic Bulge that can be addressed using these data, and describe the future plans for the survey over the coming few years.
The Construction of Stäckel Potentials for Galactic Dynamical Modelling
Authors: Batsleer P. , Dejonghe H.
Published: June 2019

We present a set of axisymmetric Stäckel potentials which can be used for Galactic dynamical modelling. Each of them has a halo–disk structure with a flat rotation curve.
Analytical models for rotating and flattened perturbations in bulges
Authors: Dejonghe H. , Vauterin P.
Published: June 2019

A power series approach for solving the linearized transport equation for perturbations in the central part of flat disks is presented. The application of this method is in principle independent of the mathematical complexity of the unperturbed distribution. As an illustration, this method was used to solve the transport equation in the case of Kalnajs' Omega models.
Delayed formation of bulges by dynamical processes
Authors: Pfenniger Daniel
Published: June 2019

Two mechanisms involving purely dynamical processes can lead to the formation of a bulge after its disc: 1) small bulges (1 – 2 kpc), including box-shaped bulges and mildly triaxial bulges, can result from the formation and destruction of a bar; 2) big bulges (> 2kpc) à la Sombrero can grow following the accretion of small satellites. Fully consistent N-body simulations show that the fraction of galaxy mass accreted in this way needs to be larger than about 5%. Less accretion does not create smaller bulges, but heats the whole disc. These dynamical effects transforming Hubble types from SB to SA and vice-versa over ≈ 1 – 2 Gyr also indicate, by the secular growth of bulges, a general sense of galactic evolution from Sd to Sa.
The Influence of a Halo on the Evolution of Elliptical Configurations
Authors: Theede F. , Thielheim K.O.
Published: June 2019

Results of n-body simulations of self-gravitating systems containing 100,000 particles are presented. A program based on the particle-mesh method is used to compute the evolution of a hot stellar-disk till an oval configuration at the center is formed. The system is evolved again from this point onwards a) with halo, b) without halo, and c) with the halo but with total mass of the system reduced to that of case b. Results are presented in form of a diagram showing the development of ellipticity.
Analytical models for ellipticals and bulges with rotation
Authors: Nuritdinov S.N.
Published: June 2019

The results of the analytical study of two disspationless non–linear models are generalized in case of rotation.
The Counter-Rotating Twin Disks in NGC 4550
Authors: Rix Hans-Walter , Franx Marijn , Fisher David , Illingworth Garth
Published: June 2019

We discuss the striking kinematic properties of the S0 galaxy NGC 4550. A detailed analysis of the line-of-sight velocity distribution (LOSVD) along the major axis shows that this galaxy contains two cold, cospatial, counterrotating disks with indistinguishable scale lengths and luminosities. The two disks, twins save the signs of their spin, are also found to have exponential luminosity profiles. We discuss qualitatively how this system might have formed.
Stellar Kinematic Evidence for Massive Black Holes Revisited
Authors: Rix Hans-Walter
Published: June 2019

The existing stellar kinematic evidence for massive black holes at the centers of galaxies is based on ≲ 30% discrepancies between constant M/L models and kinematic data. We show that asymmetries in the observed velocity distributions may introduce systematic errors in the data/model comparisons which are of the same order and have the same sign as these discrepancies. Existing modeling has so far failed to account properly for these asymmetries. Major axis data of M32 are analyzed as a specific example.
Grains in Diffuse Clouds: Carbon-Coated Silicate Cores
Authors: Williams David A.
Published: June 2019

A new model of interstellar grains is proposed in which grains in diffuse clouds consist of small (radius ≲ 10nm) and large asymmetric (0.05μm – 0.25μm) silicate cores thinly coated with mantles of amorphous carbon (thickness ≲ 5nm). This model can account successfully for many of the observed properties of interstellar dust and gives a simple interpretation of the interstellar extinction curve. The extinction bump at 220nm is attributed to absorption by finely divided silicates, as indicated by laboratory data. The large silicates provide a “grey” background extinction through the visual and UV, but the bulk of the extinction in this region is attributed, on the basis of laboratory data, to the amorphous carbon coatings. The average interstellar carbon depletion required in this model is about 50%.

Wide variations in the observed interstellar extinction along different lines of sight are well known. These variations have a natural explanation in this model in terms of two parameters: the thickness of the carbon coatings, and the proportion of graphitic to diamond-like structure within the amorphous carbon. The underlying silicate cores are generally unchanged in these variations. The average interstellar extinction curve requires roughly equal proportions of graphitic and diamond-like forms of amorphous carbon. A higher graphitic fraction produces more visual extinction and a higher diamond-like fraction produces more far UV extinction. Varying both the proportions, and the total carbon content encompasses a wide range of extinction curve shapes.

Amorphous carbon deposited at low temperature is generally diamond-like. Temperature excursions in the material reduce the hydrogen content and enhance the graphitic nature of the material. In the interstellar medium, this process has a time scale ≳ 106 yr. Carbon coatings are therefore expected to be deposited in the interstellar medium in diamond-like form and to be slowly converted to graphitelike. The growth of carbon mantles will be reversed by intermittent shocks Thus, interstellar space should contain grains with a range of thicknesses of carbon coatings, and compositions between graphitic and diamond-like.

The chemical and physical properties of amorphous carbon have been the subject of intensive laboratory study. These properties enable an understanding of a variety of observations of dust (especially in the IR) and lead to a number of predictions which are described in this paper.
VLBI Observations of the Radio Jet in 3C 273
Authors: Unwin S. C. , Davis R. J.
Published: June 2019

We present a new high dynamic range map of the quasar 3C 273, made from observations with a VLBI network of 12 telescopes. This new map at 18 cm wavelength has one of the highest dynamic ranges yet achieved with VLBI, and it shows the ‘jet’ extending to at least 180 milliarcsec, or 330 pc from the nucleus of the quasar. Strong limits can be placed on the brightness of any ‘counter-jet’ on kiloparsec-scales, as no emission is visible on the opposite side of the ‘core’. Combining with other VLBI, VLA and MERLIN maps shows that the jet is visible and continuous over a very large range of scales, from 1 pc to 40 kpc.
Electrodynamics of the Central Regions of Active Galactic Nuclei
Authors: Salvati M.
Published: June 2019

We review the information available on some bulk properties of the non-thermal emission regions in Active Galactic Nuclei, such as streaming motions, nature of composing particles, brightness temperature in the proper frame. Most of the information concerns the compact radio emission at relatively large distances from the center, whereas most of the action is thought to occur in the innermost regions which are observed at higher frequencies. We investigate whether these bulk properties can be understood within a general scheme for energy transport and particle acceleration around a magnetized rotating body.
Kinematic and Dynamical Models of Small Structures in Radio Sources
Authors: Lind Kevin R.
Published: June 2019

Models of the small-scale structures in radio sources are limited by the resolution, dynamic range, and sensitivity of the observations upon which they are based. However, evidence from variability, brightness, and proper motion observations strongly support the contention that these objects involve directed outflow or ejection of material at relativistic speeds. The evidence for relativistic motion will be discussed, and a variety of models involving both bulk and pattern motion will be analyzed in terms of spatial and temporal characteristics which may distinguish between models. The possibilities and hazards of generalizing nonrelativistic jet models to the relativistic case will also be briefly discussed, especially regarding possible observational signatures of magnetized versus unmagnetized jets.
Complete Samples of Flat Spectrum Radio Sources from the Parkes 2.7 GHz Survey
Authors: Jauncey David L. , White G. L. , Harvey B. R. , Batty M. J. , Wright A. E. , Savage Ann , Peterson B. A. , Peters W. L. , Reynolds J. E. , Gulkis S. , Preston R. A. , Morabito D. D. , Tzioumis A. K. , Condon J. J. , Malin D. F. , Nicolson G. D. , Nothnagel A.
Published: June 2019

We are investigating complete samples of southern hemisphere flat spectrum extra-galactic radio sources drawn from the Parkes 2.7 GHz Survey (see Bolton et al. 1979 and references therein). These samples are being used for a variety of investigations, including a determination of the space distribution and luminosity function of radio QSOs, their radio size distribution, as well as the structures of the individual sources. Accurate positions are being determined, as well, in order to establish an extra-galactic position reference frame in the southern hemisphere.
Structural Variability in the Core of 3C147
Authors: Alef W. , Preuss E. , Kellermann K. I. , Whyborn N. , Wilkinson P. N.
Published: June 2019

We have observed the core of the steep spectrum compact quasar 3C147 at a wavelength of 6 cm with an intercontinental VLBI array. The three observing epochs cover a period from 1981.25 to 1984.8. The core of 3C147 exhibits a complex, nonlinear, and asymmetric structure. It shows structural variability as well as variations of individual components. The observed changes in separation corespond to an apparent velocity of 2.6 ±1.0 c (H0= 50 km s−1Mpc−1, q0= 0.5). In addition a map from the 3-station observation in 1978 is presented.
BL Lacertae's Compact Variations, 1980–86: A Polarized, Superluminal Challenge
Authors: Phillips Robert B. , Mutel Robert L.
Published: June 2019

BL Lac shows tightly correlated events in flux density and polarization. When the time scale slows enough for VLBI observations to track them, moving features which mimic piston-driven shocks seem to carry the disturbances. Evidence for BL Lac's shocks may ameliorate the difficulties posed by the excessive incidence of superluminal motion among core objects; superluminal motion may arise from any number of conditions combining shocks and optical depth, not just real jet or real component motions.
High Resolution Observations of Low frequency Variables at 932 MHz
Authors: Bååth Lars B.
Published: June 2019

Fifteen sources known to be varying at low frequencies have been observed at six epochs during 1983–84 with a global VLBI array. Some of the sources show structural variations similar to the superluminals. Beaming effect may therefore play an important role at low frequencies as well as at higher.
VLBI Observations of Compact Extragalactic Radio Sources with Steep Spectra
Authors: Kulkarni V. K. , Romney J. D.
Published: June 2019

In recent years it has become clear that the common practice of dividing radio sources into two classes, compact flat-spectrum sources and extended steep-spectrum sources is too simplistic and that compact steep-spectrum sources (CSS) sources which seem to form a separate class in themselves, need to be taken into consideration. A majority of flat-spectrum sources are known to show asymmetric or D2 structures. In contrast to this many CSS sources when observed with subarcsecond resolution show symmetric structures typical of extended steep-spectrum sources. However, further high resolution observations of CSS objects are clearly needed to establish the structural differences, if any, between the two types of compact objects and to understand the interrelationship between the three classes of objects. In this connection we have undertaken a program to observe a sample of 18 CSS sources using the European VLBI network. The sample was selected from the compilation by Peacock and Wall (1982), according to the following criteria: (1) flux density > 1.8 Jy; (2) largest angular size < 1 arc sec; and (3) steep high frequency spectral index (> 0.5) and high degree of low frequency spectral curvature. Our aim was to find out the structures common to these sources and their relation to more commonly observed “centimetre excess” compact objects. Here we will present the preliminary results.