bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast and Slow Bars: A Comparative Analysis
Authors: Polyachenko Valerij L. 
Published: July 2016

AbstractThe in-plane appearance of barred galaxies is formed in either of two ways: 1) the usual bar-mode instability in a fast rotating disk forms a fast bar, while 2) the radial orbit instability (or its modifications) leads to a slow bar. The vertical structure depends on the universal mechanism of the bending instability both in fast and slow bars. Among all the relevant topics, I chose (i) a critical review of the work on the bending instability, and (ii) some comments concerning the local and global stability criteria for non-axisymmetric disturbances in galactic disks; in particular, a new approximate local dispersion relation for a star disk is presented. Also shown is a range of accuracy for the intuitional global criterion of the slow bar instability of the Ostriker-Peebles type (on the example of the exactly-solved model).
Test Particle Simulations of Ringed Barred Galaxies
Authors: Rautiainen P. , Salo H. , Byrd G. , Buta R. , Crocker D. A. 
Published: July 2016

We have made test particle simulations of the gas component in barred galaxies. The potential consists of two parts: an axisymmetric isochrone potentialand a bar potential Φ1(r, θ) = Φb(r)cos(2θ), whereThe bar strength, q, and scalelength, a, are chosen so that the relative nonaxisymmetric force reaches its maximum, 10%, at the distance which is 83% of the corotation radius. The potential and its scaling are the same as in Schwarz (1981).
Fabry-Perot Observations and Hydrodynamical Simulations of the Barred Spiral NGC 4123
Authors: Weiner Benjamin J. , Sellwood J. A. , Williams T. B. 
Published: July 2016

AbstractWe present Fabry-Perot observations of the velocity field of gas in the barred spiral NGC 4123, and 2-D hydrodynamical simulations of the gas flow in model potentials derived from I-band photometry. The simulated gas flow is quite sensitive to the details of the potential, which enables us to constrain parameters such as the M/LI of the bar and the bar pattern speed. The observations confirm that the dust lanes along the leading edges of the bar are the locations of shocks. Requiring models to produce shocks with the correct alignment constrains the Lagrange point L1 (corotation) to be at a radius 1.1 – 1.4 times the semimajor axis of the bar, i.e. the bar is a fast rotator.
N-body Simulations of Two-Component, Bar-Unstable Disks
Authors: Kaufmann David E. 
Published: July 2016

AbstractWe present results of numerical simulations of bar-unstable disks that include a dissipative gas component. The simulations have been carried out using a two-dimensional polar grid for the force calculations. The gas component has been modelled as a collection of finite-sized particles that dissipate a fraction of their relative motion during collisions.
Widths of Lindblad Resonances in Galaxies: Origin of the Hole in the Gas Disk of the Milky Way
Authors: Marochnik Leonid , Sagdeev Roald , Usikov Daniel 
Published: July 2016

AbstractIt is shown that slopes of p(R) = Ω(R) ± κ(R)/m curves at Lindblad resonances determine the widths of resonance regions. The ability of galactic disks to respond to torques exerted at ILRs by perturbers (bar, density wave, galaxy-satellite, etc.) is determined by the widths of inner Lindblad resonances (ILRs). Widths of ILRs vary along the Hubble sequence of normal and barred galaxies. Galaxies having the bulge to disk ratio of masses and radii similar to the Milky Way could have wide ILRs if they are formed at the region of 2-4 kpc from their centers. A wide range of possible perturbers with pattern speeds 4≤ Ωp ≤ 26 km s≤1 kpc−1 could excite an ILR at this region of the Milky Way. Probably, the ILR of Milky Way’s grand design is located in the same region. The hole in the galactic H2 disk is also located in this region. The mechanism responsible for the origin of this hole could be similar to that opening gaps in planetary rings.
A Self-Consistent Dynamical Model for the COBE Observed Galactic Bar and Its Application to Microlensing
Authors: Zhao HongSheng 
Published: July 2016

AbstractA self-consistent stellar dynamical model for the Galactic bar is constructed from about 500 numerically computed orbits with an extension of the Schwarzschild technique. The model fits the COBE found asymmetric boxy light distribution and the observed stellar kinematics of the bulge. The model potential is also consistent with the non-circular motions of the HI and CO velocity maps of the inner Galaxy. We also use the stellar bar model to construct an N-body model to study stability and a microlensing map towards the bulge, which can account for the observed optical depth and the event duration by the MACHO and OGLE collaborations. The technique used here can be applied to interpret light and velocity data of external bulges/bars and galactic nuclei.
A Sober Look at Bars in Galaxies
Authors: Keel William C. 
Published: July 2016

AbstractI review some of the more notable observational aspects of bars in galaxies. Key issues include the overall occurrence of bars, secular evolution of bars and bulges, the differences in bar properties with Hubble type, the role of bars in star formation and nuclear activity, and the evidence for a bar at the center of the Milky Way. These lead to a “wish list” of future observations.
Magnitudes and Spectra of Important Dynamical Phenomena
Authors: Fedotov E. P. 
Published: July 2016

AbstractThe axes of coordinate systems used in geodynamics are believed to be attached to a number of physical points on the surface of the Earth. This is true when measurements of the distances (ranging) are dealt with. On the other hand, the axes of reference systems used by the BIH and IFMS are attached not to the points themselves but to a pencil of plumb lines at these points. For the case of observations with radio interferometers being used for the study of Earth’s rotation, the rotating frame of reference could be attached in some prescribed way toihebaselines of the interferometers.But in no case is rigid attachment possible, because both the above points and lines move relative to each other. We should search for another way to define the reference systems for geodynamics. With that end in view, a knowledge of magnitudes of pertinent dynamical phenomena becomes vital.This paper considers the effects of some dynamical phenomena upon the distances between the points on. the Earth’s surface and upon the angles between plumb lines and, possibly, also between baselines of radio interferometers. In particular, this paper discusses body tides, continental drift, internal motion within crustal blocks, redistribution of mass which can affect the directions of plumb lines, etc. Polar motion and variations in the rate of Earth’s rotation will be also touched upon as far as these phenomena contribute to deformation of the Earth and its gravitation field.The results are summarised in diagrams showing how the variations of the above distances and angles depend upon both time and positions on the Earth. In other words, the power spectrum of the variation will be presented as a function of time and distance expressed either in kilometers or in degrees of arc on the Earth’s surface.
2.1.5 Flux of Hyperbolic Meteoroids
Authors: Dohnanyi J.S. 
Published: July 2016

AbstractThe production of hyperbolic meteoroids by inelastic collisions between meteoroids is estimated. It is found that, under reasonable assumptions, the calculated flux of hyperbolic meteoroids agrees with satellite data and with lunar microcrater distributions.We have therefore obtained independent theoretical support for Zook and Berg’s (1975) ß-meteoroid hypothesis and for Fechtig et al. (1974) suggestion that submicron lunar microcraters are produced by ß-meteoroids.
2.1.8 Sources of Interplanetary Dust: Asteroids
Authors: Dohnanyi J. S. 
Published: July 2016

AbstractThe asteroid belt is examined as a potential source of interplanetary dust. Using results from the Pioneer-10 experiments the relative contribution of asteroidal and cometary particles to the Zodiacal cloud is estimated using methods developed in earlier studies of meteoroidal collisions (collisional model). It is found that the contribution of asteroidal particles to dust in the asteroidal belt is small compared with the number density of cometary type particles. Similar conclusions apply to the Zodiacal cloud between the sun and the asteroid belt. When definitive criteria for differentiating between comets and asteroids become available, a reexamination of some of our conclusions may become necessary.The distribution of asteroidal rotations is analyzed; it is found that the gross features of the distribution can be reproduced using the collisional model.
3.1 Dust in Comets and Interplanetary Matter
Authors: Vanýsek Vladimir 
Published: July 2016

SummaryResults of many current attemps to estimate the physical and chemical composition of dust particles in comets are reviewed and discussed. It is shown that even the most basic parameters, such as albedo of the cometary dust, are not properly known at the present time. The emission feature in the infrared spectra of comets, which resembles those observed in the interstellar (and circumstellar) clouds and which indicates a relation between the general composition of comets and interstellar matter, is widely ascribed to silicates. Similar features may, however, be also caused by polymerized molecules or hydrocarbons mantles of the dust grains.
5.2 Dynamics of Interplanetary Dust and Related Topics
Authors: Trulsen Jan 
Published: July 2016

AbstractThe problem of the effects of mutual collisions for the dynamics of interplanetary dust particles and grains is reviewed. Collisions are shown to give a rather characteristic dynamical signature, the importance of these effects depending mainly on the mean free collision time and the degree of inelasticity. Although a few attempts to look for collisional effects in the solar system have been made, rather much work remains to be done before the problem is fully understood.
5.3 Modeling of the Orbital Evolution of Vaporizing Dust Particles Near the Sun
Authors: Sekanina Zdenek 
Published: July 2016

AbstractThe Poynting-Robertson (P-R) effect (Robertson, 1937, Wyatt and Whipple, 1950), assisted by a pseudo P-R effect due to the sputtering (Whipple, 1955, 1967), is known to cause small dust particles in interplanetary space to spiral toward the sun. Evaporation from the surface of such particles thus increases progressively with time and their size is being reduced accordingly. When the rate of evaporation is no longer negligibly low, it induces on the particle a measurable dynamical effect, which is associated with the implied variations in the magnitude of solar radiation pressure relative to solar attraction. By gradually reducing solar attraction, the particle evaporation tends to increase the orbit dimensions, thus acting against P-R. The P-R inward spiraling, far exceeding the dynamical effect from evaporation at larger heliocentric distances, slows gradually down as the particle approaches the sun, and virtually ceases when the critical distance is reached, where the two forces approximately balance each other. Then, typically, the perihelion distance stabilizes, while the eccentricity starts increasing very rapidly until the particle is swept out of the solar system. This, in brief, is the orbital evolution of a vaporizing particle in the absence of other potentially important but rather poorly known processes, such as particle collisions, rotational bursting, electric charging and interactions with the solar wind and with the interplanetary magnetic field.
5.10 Are Interplanetary Grains Crystalline?
Authors: Drapatz S. , Michel K.W. 
Published: July 2016

AbstractThe optical properties of interplanetary grains depend not only on chemical composition, size, and shape but also on lattice defects. It is argued that practically all sources for the zodiacal dust cloud yield grains with highly disturbed crystal structure. Healing of these defects can occur when the grains are heated in the vicinity of the sun (≤0.1 AU) and various orbits are considered, on which annealed grains with nearly perfect crystal structure can return to larger heliocentric distances to reveal the sharp optical features of cold well-ordered crystals. However, we do not find any processes, which produce healed particles of sufficient number to affect the properties of the general zodiacal cloud. Therefore, the optical properties of interplanetary grains are determined by a high degree of lattice perturbation.
Note on the Multiplicity of dMe Stars
Authors: Lippincott Sarah Lee 
Published: July 2016

AbstractThere is much current interest in flare stars of the type dMe with particular concern as to their ages and mechanism responsible for flaring. Some fifty Me stars are on the Sproul Astrometric program. They have been discussed as flare stars or potential flare stars (Lippincott 1971). At least half are known to be members of binary or multiple systems. All are on the Sproul program to obtain accurate parallaxes and to analyze the long interval observations for non-linear proper motions indicating unseen companions. The astrometric results are discussed and statistics presented for the multiplicity among these nearby systems.
Kappa Pegasi—A Quadruple System of Possible Low Total Mass
Authors: Beardsley W. R. , King M. W. 
Published: July 2016

AbstractAnalyses of early Lick Obs. spectra and recent high dispersion Kitt Peak National Obs. spectra indicate that k Peg is a quadruple system having all four spectra visible under favorable conditions. Preliminary spectroscopic orbital elements are presented for the AB system, and for Bb. The Bab system has been found to be the previously known 5.97-day spectroscopic system. The total mass is found to be between 2 and 3 solar masses only. Thus the brightest of the four stars Ba(F5IV) —or possibly all four of the stars—must have an abnormally small mass for its luminosity. This system appears to be similar to several others which have apparent overluminous components. Such systems are of interest in regard to stellar evolution.
Recherche Sur L’existence Possible D’un Compagnon Astrometrique Dans Le Couple Visuel Ads 9476 — Aitken 14
Authors: Mourão R. R. De Freitas 
Published: July 2016

AbstractObservations made during the 70 last years of the visual binary star Aitken 14 reveal systematic deviations in its motion, suggesting the existence of an astrometric companion.
Three Dimensional Stability of A Rectilinear Periodic Solution of the Three-Body Problem, for all Values of the Masses
Authors: Hénon M. 
Published: July 2016

AbstractWe consider a rectilinear periodic solution in which the central body collides alternately with each of the two other bodies. This solution is found to exist for all values of the three masses. Its stability with respect to three-dimensional perturbations is computed. Domains of stability and instability are delimited in a triangular mass diagram. Large domains of stability are found. This reinforces the conclusion that triple stars may have an “interplay” type of motion.
A New Trapezium System Associated with A Compact H II Region
Authors: Sharpless S. , Pipher J.L. , Savedoff M.P. 
Published: July 2016

The region S106 = G 76.4 — 0.6 has been photographed in the 8000Å region with the Carnegie image converter attached to the 0.6m telescope at the Mees Observatory. This was done in connection with a larger program designed to assemble radio, infrared, and optical data on compact HII regions.S106 has angular dimensions of 1’ by 3’ and has relatively high surface brightness. Its kinematic distance based on H109a observations (Reinfenstein, et al. 1970) is 2.3 kpc ± 3.0.Several bright maxima are observed within the nebula at wavelengths of 12.6/x and 2.7 GHz. These are believed to be the result of thermal radiation from hot dust and free-free emission from ionized gas, respectively. At the nominal distance their linear sizes are of the order of 0.2 pc and they may be similar to the “cocoon” type objects discussed by various authors.
Mutiple Star Formation from N-Body System Decay
Authors: Harrington R. S. 
Published: July 2016

AbstractThe dynamical decays of random, unstable, negative-energy, n-body systems have been followed numerically, to investigate the statistics of stable decay products. From initial quadruple systems, about 20% of the products were stable triples while 30% resulted from initial quintuple systems. These numbers are consistent with the observed ratio of triples to binaries, especially for the higher-multiplicity initial systems.
A Bibliography of Astronomical Catalogues and the Organization of Stellar Designations
Authors: Collins M.J. 
Published: July 2016

AbstractA comprehensive bibliography of astronomical catalogues for the period 1951-75 inclusive containing over 2000 items and including an index of designations has shown that there is an urgent need to control the use of designation notation. It is suggested that a small data base, similar to the one created for this bibliography could serve as a useful guide to the assignment and subsequent citation of catalogued objects. This in turn would help those compiling inverted files of stellar objects such as the Catalog of Stellar Identifications.
Data Distribution
Authors: Hauck B. 
Published: July 2016

Before answering, or trying to answer, the question “how to distribute astronomical and astrophysical data”, it is necessary to reply briefly to the question “why distribute these data?” This question is not so trivial as it first appears and it even hides the basic problem.Data acquisition in itself is a single or manifold technique, often very delicate, constituting in itself a whole field of research. The interpretation of data follows it and will not necessarily be made by the same people. Very often only one possible aspect will be examined. It is consequently absolutely necessary that the data should be disseminated as widely as possible in order that they are used to the utmost. If it is necessary to assure the dissemination of data, it is no less necessary to ascertain their conservation. I shall give here only one example: the observations which have permitted to obtain the light curve of the quasar 3C273.
A Master List of Non-Stellar Objects
Authors: DIXON ROBERT S. 
Published: July 2016

It has been nearly 70 years since Dreyer completed his famous NGC and IC compendia of all the 13,000 non-stellar objects known in his time. Since then, the number of these objects known has increased by an order of magnitude, but this knowledge is scattered throughout the astronomical literature in such a way that it 1s nearly inaccessible from a practical standpoint to any individual.The present work is an amalgamation of all known catalogs of non-stellar objects, in a uniform, easily readable form. It is Intended not only for astronomers, but also for scientists and engineers in other fields who have need for rapid access to this basic reference data. The types of objects included are galaxies (including both normal and all specialized types such as interacting, peculiar, dwarf, Seyfert, etc.), clusters of galaxies, nebulae of all kinds (planetary, reflection, emission, absorption, etc.), blue objects, groups of stars (open and globular clusters, associations, rings, chains, etc.), quasi-stellar objects, super-novae and others. The Information given for each object includes name, 1950.0 position, angular diameter in arcseconds, magnitude, description, and original reference. A portion of the work is shown in Figure 1. Approximately 185,000 listings appear in the full master 11st.
Stellar Data and Computing Facilities at the Pulkovo Observatory
Authors: Polojentsev D.D. 
Published: July 2016

The Pulkovo Observatory computing laboratory began its activities in 1956. Originally it was equipped with card-punched machines. An essential work of processing astronomical data was carried out with the help of these machines ([1] and other).With the development of the computing techniques in the USSR, the laboratory has been equipped with more modern computing devices. At present the Laboratory disposes of the third generation computer ES-1020 of the Ryad type, as well as the second generation computers Minsk-22 and Nairi-K.
Report of Discussions
Authors: Wilkins G. A. 
Published: July 2016

SummaryThis report summarises the discussions on the topics of the five invited papers, and on other matters of general interest that were raised by the contributed papers. The principal headings are: standards for datafiles; the influence of acquisition and processing techniques; the critical evaluation of data; the designation of astronomical objects; the distribution of data; survey of facilities; the future role of data centres; and recommendations on IAU activities.
Distances of nearby Groups and Clusters, and the Local Value of the Hubble Ratio
Authors: Vaucouleurs G. de 
Published: July 2016

AbstractThe correct approach to build up the extragalactic distance scale is to use all available primary (novae, cepheids, RR Lyrae) and secondary indicators (brightest stars, globular clusters, largest HII rings) to calibrate without arbitrary extrapolation all reliable tertiary indicators (magnitudes and diameters of galaxies), precisely corrected for all known effects of type, luminosity class, orientation, internal and galactic extinction and redshift. Such data are now available for over 1000 galaxies in the Second Reference Catalogue.Revised distances to members of the Local Group from primary indicators and new estimates of distances to the nearest groups from primary and secondary indicators are used to calibrate the tertiary indicators via a new, composite luminosity index.The distances derived from globular clusters for 3 galaxy clusters dominated by ellipticals (Vir I, For I, Hya I) with mean corrected velocities 1000 ≤ Vo ≤ 3650 km s-1 give a mean Hubble ratio <H> = 88 (1 ± 0.15) km s-1 Mpc-1. This value rests entirely on the calibration of the globular clusters luminosity function in the Galaxy as a gaussian of dispersion σ = 1.1 mag. and mean <MB>(⊕) = -6.55, with <(B-V)o > = 0.75, based on the adopted RR Lyrae zero point <Mv> (RR) = + 0.86 ± 0.15.The distances derived from tertiary indicators to 19 field spirals and 28 nearby groups dominated by spirals with corrected velocities Vo < 1800 km s-1 give <H> = 82 (1 ± 0.15) km s-1 Mpc-1. This value rests on the relations between luminosity index and fully corrected absolute magnitudes or linear diameters of galaxies derived without extrapolation and calibrated in ~20 nearby galaxies by seven secondary indicators. The zero points were derived from the 3 primary indicators, including 15 galactic novae with <M15> = -5.5 ± 0.15, and 13 cepheids in 8 galactic clusters with <MB> (logPo = 0.8) = -2.92 ± 0.15 (for an adopted Hyades modulus of 3.16 ± 0.05).The low values of Ho≃50 to 55 can be explained by an accumulation of complex systematic errors arising from a multiplicity of sources. These errors, all but one acting in the same sense, have been identified and evaluated; a full report will appear elsewhere.
Selection Effects at 21cm
Authors: Briggs F.H. 
Published: July 2016

AbstractSurveys in the 21cm line of neutral hydrogen are testing the completeness of the catalogs of nearby galaxies. The remarkable observational fact is that the potential wells that confine gas to sufficient density that it can remain neutral in the face of ionizing radiation also provide sites for star formation, so that there are no known cases of neutral intergalactic clouds without associated star light.