bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Broadening Functions using the Singular Value Decomposition (SVD) Technique
Authors: Rucinski Slavek
Published: July 2016

The cross-correlation function (CCF) has become the standard tool for extraction of radial-velocity and broadening information from high resolution spectra. It permits integration of information which is common to many spectral lines into one function which is easy to calculate, visualize and interpret. However, the CCF is not the best tool for many applications where it should be replaced by the proper broadening function (BF). Typical applications requiring use of BFs rather than CCFs involve finding locations of star spots, studies of projected shapes of highly distorted stars such as contact binaries (as no assumptions can be made about BF symmetry or even continuity) and [Fe/H] metallicity determinations (good baselines and avoidance of negative lobes are essential). It is stressed that the CCFs are not broadening functions. This note concentrates on the advantages of determining BFs through the process of linear inversion, preferably accomplished using the singular value decomposition (SVD). Some basic examples of numerical operations are given in the IDL programming language.
Distinction between Extra-solar Planets and Low-mass Secondaries
Authors: Mazeh Tsevi
Published: July 2016

This paper discusses the distinction between extra-solar planets and low-mass secondaries, in principle as well as in practice. Adopting a distinction based on the presumed different processes of formation, the paper compares the characteristic features of the giant planets in our solar system with those of the low-mass secondaries in spectroscopic binaries. The discussion reveals that there is no a priori obvious feature that can identify planets. Instead, this work considers the extremely small emerging population of discovered extra-solar planets. Based on the nine “planet-candidates” discovered as of mid-1998, it was found that their mass distribution is remarkably different from the distribution of low-mass secondaries. The transition between the two populations probably occurs at 10−30 Jupiter masses. This transition could reflect the borderline between planet and brown dwarf secondary masses.
Radial Velocity Observations of Non-radially Pulsating Stars
Authors: Hatzes A. P. , Kanaan A. , Mkrtichian D.
Published: July 2016

The rapidly oscillating Ap stars (roAp) are a class of nonradially pulsating stars oscillating in low-degree modes with periods of 4–15 minutes. We have started a program to study the oscillations on several roAp stars using precise radial velocity (RV) measurements. The typical mean RV amplitude for the roAp stars we have observed is 50–400 ms−1, but this amplitude depends on the spectral region used for the measurement of the RV amplitude. A detailed line-by-line analysis reveals that the pulsational amplitude depends not only on atomic species, but on the line strength as well. For a given atomic species weak spectral lines exhibit a pulsational amplitude 10–100 times higher than for strong lines. The elemental effect can be understood in the context of the inhomogeneous distribution of elements known to occur on these stars and that is believed to result from the global dipole magnetic fields that are present. For instance, if an element is concentrated near the magnetic pole then it may have a higher RV amplitude than one that is distributed about the magnetic equator. The line strength effect is interpreted as arising from vertical structure to the pulsations since weaker lines are formed, on average, deeper in the atmosphere than stronger lines. Precise RV measurements may prove to be a powerful tool for probing both the vertical and horizontal structure of the pulsations in roAp stars.
Possible Detection of p-mode Oscillations on Procyon
Authors: Barban C. , Michel E. , Martic M. , Schmitt J. , Bouchy F. , Lebrun J.C. , Connes P. , Bertaux J.L. , Baglin A.
Published: July 2016

We have observed Procyon with the fiber-fed échelle spectrograph ELODIE coupled with a Fabry-Perot etalon at the 193-cm of the Observatoire de Haute Provence (France) over 5 nights during 1997 December – 1998 January. Here, we present the results of a search for solar-like oscillations on this star and the performance of this instrumentation for asteroseismology. The power spectra show an excess of signal between 0.42 mHz and 1.46 mHz, which could be due to stellar oscillations.
A Program for the Analysis of Long-Period Binaries: The Case of ϒ Delphini
Authors: Irwin Alan W. , VandenBerg Don A. , Larson Ana M.
Published: July 2016

Binary systems can be analyzed like clusters but with additional constraints from the orbit. The theories of stellar interiors and atmospheres are used to analyze the color-magnitude diagram and spectra to test the consistency of theory and observation and also to provide results on the distance, chemical composition, age, and individual masses, radii, and effective temperatures. Given the total mass resulting from the theoretical analysis, it is possible to determine the complete orbit of even long-period binaries if at least 6 components of the position, velocity and acceleration vectors have been observed.

For this paper we apply such a theoretical and orbital analysis to the ϒ Delphini binary consisting of a K1 IV primary (ϒ2 Del) and an F7 V secondary (ϒ1 Del). The primary has been observed with the preciseradial-velocity (PRV) technique and shows a radial acceleration of 2.2 ± 0.7 m s−1 yr−1 as well as a significant (false alarm probability < 0.01) periodic signature (P = 1.44 yr). At least three possible causes of this periodic signature are pulsation, rotation, or a planetary companion. The mass and radius results (M2 = 1.72M⊙, M1 = 1.57M⊙, R2 = 6.43R⊙, and R1 = 2.21R⊙) of our theoretical analysis help constrain the possibilities. The pulsational hypothesis requires more investigation of whether it is possible to excite a g-mode or an r-mode period that is much longer than the fundamental period of 0.5 dy derived from the mass-radius results. The rotational hypothesis leads to an inconsistency; the published value of υ sin i is a factor of 4.5 larger than the maximum value allowed by the radius and the PRV period of 1.44 yr. More investigation is required to determine whether increased macroturbulence and decreased υ sin i (by a factor of 4.5) is consistent with observed line profiles. From the PRV period and the primary mass a possible planetary companion would have υ sin i = 0.7 Jupiter masses with an orbital semimajor axis of 1.5 AU. The orbital results for the stellar binary (closest approach > 15 AU) shows there is room in the system for such a possible planetary companion of ϒ2 Del to survive the gravitational perturbations of ϒ1 Del.
A Method of Measuring Gamma-Velocities of Contact Binary Stars
Authors: Kaszás G. , Vinkó J. , Fürész G.
Published: July 2016

Gamma-velocities of bright contact binary stars (VW Cep, SW Lac, AB And, OO Aql) have been computed using cross-correlation. The template spectra were synthesized with a newly developed computer code WGMODEL.
Spectroscopic Orbit of the Eclipsing Binary BD +52°2009
Authors: Khalesseh B.
Published: July 2016

New radial velocity measurements of the Algol-type eclipsing binary BD +52 °2009, based on Reticon observations, are presented. The velocity measures are based on fitting theoretical profiles, generated by a physical model of the binary, to the observed cross-correlation function (ccf). Such profiles match this function very well, much better in fact than Gaussian profiles, which are generally used. Measuring the ccf’s with Gaussian profiles yields the following results: mp sin3i = 2.55 ± 0.05m⊙, ms sin3i = 1.14 ± 0.03m⊙, (ap + as) sin i = 7.34 ± 0.05R⊙, and mp/ms = 2.23 ± 0.05. However, measuring the ccf’s with theoretical profiles yields a mass ratio of 2.33 and following results: mp sin3i = 2.84 ± 0.05m⊙, ms sin3i = 1.22 ± 0.03m⊙, (ap + as) sin i = 7.56 ± 0.05R⊙. The system has a semi-detached configuration. By combining the solution of a previously published light curve with the spectroscopic orbit, one can obtain the following physical parameters: mp = 2.99m⊙, ms3 = 1.28m⊙, < Tp >= 9600K, < Ts >= 5400K, < Rp >= 2.35R⊙, < Rs >= 2.12R⊙. The system consists of an A0 primary and a G2 secondary.
On the Binarity of the F0p Magnetic Stars ϒ Equ and 49 Cam
Authors: Mkrtichian D.E. , Samus N.N. , Gorynya N.A. , North P. , Hatzes A.P.
Published: July 2016

The magnetic field investigations of the rapidly-oscillating (ro)Ap star ϒ Equ show a very long magnetic (rotational) period of about 74 years (Leroy et al. 1994; Bychkov & Shtol 1997). No significant changes of radial velocities were detected during the history of investigations of this star. Recently, Scholz et al. (1997) (hereafter S97) reported a rapid increase of radial velocity (RV) of ϒ Equ from the mean value of -16.81 km s−1 up to a maximum at -4.28 km s−1 within the interval JD 2449608 – JD 2450356, and suggested that ϒ Equ is a long-period binary star with high eccentricity. Such a probable discovery of binary motion of ϒ Equ is very interesting, since it opens the possibility to compare asteroseismic parameters of the star with those obtained from the binary orbit.
Radial-Velocity Standard Stars
Authors: Stefanik Robert P. , Latham David W. , Torres Guillermo
Published: July 2016

We review the history of the IAU Radial Velocity Standard Stars and give a status report on recent efforts at the Harvard-Smithsonian Center for Astrophysics to establish an absolute velocity zero point for these stars and to improve their usefulness for intercomparing the results from different instruments and observatories.
Retrospect
Authors: Walker Gordon A.H.
Published: July 2016

What an excellent colloquium! The measurement of precise radial velocities is now firmly established in the arsenal of observational astronomy and complements the spectacular improvements in astrometric precision from space and interferometry from the ground. Announcements of candidate planets have generated a huge amount of scientific and public interest and provided NASA with copious free publicity for its Origins program. The mapping of stellar surfaces and the probing of their interior structure from nonradial pulsations must be among the most exquisite measurements in science. We have celebrated all of these achievements here. It is quite ironic and a sad reflection on priorities that so many of the most exciting contributions were from authors without permanent positions.
A Determination of Meteor Mass Distribution From Meteor Echoes
Authors: Forti G.
Published: July 2016

Meteor counts from the observations of the Harvard-Smithsonian Radio Meteor Project at four magnitudes in the range of about +9 to +15 in the visual scale were used to determine the exponent of the mass-distribution law under certain assumptions. Since for these data no range measures were available, and since the pattern of the transmitting/receiving antennas was very broad, the same range and radiant distribution were assumed for all counts within the same half-hour during which individual counts at different magnitudes were obtained. These echo counts, covering in five successive days 24 hr with overlapping periods, yielded for the exponent a value of 1.95±0.0.02, close to other determinations. Individual values, however, presented a considerable scatter, probably reflecting changes in radiant and mass distribution over the year. From the same data, it appeared that the mass exponent changed during the day, yielding generally a higher value for the evening hours.
The Distribution of 1/a in Photographic Meteor Orbits
Authors: Lindblad B. A.
Published: July 2016

A study is made of the distribution of reciprocal semi-major axis in photographic meteor orbits. A detailed classification of the orbits is made according to quality. The distribution of 1/a in precise orbits is multimodal with two broad maxima approximately centered on 0.05 and 0.40 (AU)-1. Minima in the distribution appear near 0.20 and 0.66 (AU)-1 corresponding to Jupiter’s and Mars’ position in the 1/a, diagram. Considerable fine structure appears in the 1/a distribution. Resonance gaps corresponding to commensurabilities with Jupiter are detected. The gaps are similar to the well studied Kirkwood gaps in the asteroid beli.
Lunar Rocks as Meteoroid Detectors
Authors: Hartung Jack B. , Hörz Friedrich , Gault Donald E.
Published: July 2016

About 5000 microcraters on seven lunar rocks recovered during the Apollo 12 mission have been systematically studied using a stereomicroscope. Based on comparisons with laboratory cratering experiments, at least 95 percent of all millimeter-sized craters observed were formed by impacts in which the impact velocity exceeded 10 km/s. The dynamics of particle motion near the Moon and the distribution of microcraters on the rocks require an extralunar origin for these impacting particles.

The microcrater population on at least one side of all rocks studied was in equilibrium for millimeter-sized craters; i.e., statistically, craters a few millimeters in diameter and smaller were being removed by the superposition of new craters at the same rate new craters were being formed. Selected surfaces of some rocks, particularly those with glass coatings, are not in equilibrium. For every particle incident upon these “production” surfaces, there remains for observation a corresponding crater; thus the population of craters on such a surface is directly related to the total population of particles impacting that surface.

Crater size-distribution data from production surfaces, together with an experimentally determined relationship between the crater size and the physical parameters of the impacting particle, yield the mass distribution of the interplanetary dust at 1 AU. Based on assumptions corresponding to an impact velocity of about 20 km/s and a particle density of 3 g/cm3, the cumulative particle flux versus mass distribution relationship is

where N is the number of particles of mass m in grams, and larger, and C depends on the time-area product, which is, for the present, unknown. For particles smaller than 10-8 g, our observations indicate a sharper decrease in the absolute value of the slope of the flux versus mass curve than is indicated by satellite-borne-experiment data. This result may be due to a genuine relative decrease in the number or kinetic energy of smaller particles, or it may be due to our inability to observe quantitatively the smallest microcraters. For particles larger than 10-6 g, the slope of the flux versus mass curve increases smoothly to an absolute value greater than one.
Artificial Meteor Ablation Studies
Authors: Blanchard Maxwell B.
Published: July 2016

Artificial meteor ablation was performed on natural minerals, composed predominately of magnetite and hematite, using an arc-heated plasma stream of air. Analysis of the ablated debris indicates most was composed of two or more minerals. Wustite, a metastable mineral, was found to occur as a common product. The “magnetite” model, whose content was 80 percent magnetite, 14 percent hematite, 4 percent apatite, and 2 percent quartz, yielded ablated products consisting of over 12 different minerals. Magnetite occurred in 91 percent of all specimens examined, hematite in 16 percent, and wustite in 39 percent. The “hematite” model, whose content was 96 percent hematite and 3 percent quartz, yielded ablated products consisting of over 13 different minerals. Hematite occurred in 47 percent of all specimens examined, magnetite in 60 percent, and wustite in 28 percent. The more volatile elements (Si, P, and Cl) were depleted by a reduction of about 50 percent in the amounts present. Also, the relative abundance of Fe increased as a result of both volatile depletion (loss of Si, P, Cl, and Ca) and a reduction in its oxidation state. Hematite was converted to magnetite in the ablation zone along the model’s front face. Also, quartz and apatite minerals were converted to an Fe-rich glass consisting of varying amounts of Si, P, Cl, and Ca, depending upon the accessory minerals available at the time of melting. These glass phases occurred as unusual myrmekiticlike intergrowths, which are unique textural indicators of the environment through which the material has survived. The chemistry and mineralogy of these phases remains the only trace of the original minerals. This study has shown that artificially created ablation products from iron oxides exhibit unique properties that can be used for their identification. These properties depend on the composition of the original material and the environmental conditions of formation. In addition to the accepted elemental criteria, these properties are morphologic characteristics, textural parameters, and the existence of metastable minerals.
A Possible Mechanism for the Capture of Microparticles by the Earth and Other Planets of the Solar System
Authors: Benedetto F. Di
Published: July 2016

By application of Lyttleton’s theory for the formation of comets, it is shown that a possible mechanism for the origin and formation of a concentration of cosmic particles around the Earth and the other planets of the solar system exists.

In the vicinity of the neutral point, where the velocity of colliding particles is not greater than 6 km/s, it is found that if the solid particles after collision must remain in a solid state, there can be no possibility of accretion for Mercury, Mars, and the Moon, where the maximum value of the “closing-in parameter” p (distance of the center of the planet to the asymptotic trajectory) is less than the radius of the planet.

On the other hand, the capture radii of microparticles in solid form varies from a minimum of 2.95 planetary radii for Venus and 3.47 for the Earth, to about 986 for Jupiter.
The Physical Nature of Interplanetary Dust as Inferred by Particles Collected at 35 km
Authors: Brownlee Donald E. , Hodge Paul W. , Bucher William
Published: July 2016

Particles were collected at an altitude of 35 km by two flights of a volume-sampling micrometeorite collector. The collection scheme is very sensitive and is capable of collecting a significant number of particles. Many of the particles collected have chemical compositions similar to solar or to iron meteorites. Morphology of collected particles indicates that both true micrometeorites and ablation products were collected.
Ionized Gas in Bright Barred Spiral Galaxies: Hα Images
Authors: Garcia-Barreto J. A. , Carrillo R. , Venegas S. , Escalante-Ramirez B.
Published: July 2016

In this paper we present the spatial distribution of ionized hydrogen gas, Hα, in a set of 52 bright barred Shapley-Ames spiral galaxies. In summary we were able to detect Hα line emission from distinct regions in the galaxies as from compact nuclei, from circumnuclear rings, from the bar, from ends of bars, from inner rings, from spiral arms, from outer rings and from places or structures perpendicular either to the bar or to the spiral arms.
The Shape of the Luminosity Profiles of Bulges
Authors: Andredakis Y. , Peletier R. , Balcells M.
Published: July 2016

We extract the bulge light profiles of a sample of early type spirals, using K-band photometry and a new 2-dimensional decomposition method that does not assume a priori any surface brightness laws. We find that the shape of the light profile shows a good correlation with the morphological type of the galaxy, in the sense that the profiles tend to fall off more steeply at large radii for the later types. This trend shows that the formation of or interaction with the disk has probably affected the density distribution of the bulge. The fact that the transition in shape is continuous might also imply that most of the bulges of late type spirals were not formed by different mechanisms than the ones of early types.
The Analysis of the Barred Galaxy NGC 6701
Authors: Márquez I.
Published: July 2016

Images: 1.5m Spanish telescope in Calar Alto, Thomson blue coated 1024×1024 CCD, 0.31″pixel−1. Exposition times of 1800, 1500 and 1200 (BV R) and 2000 seconds (Hα and continuum) were used. Seeing FWHM = 1″. Spectra for NGC 6701: 3.5m telescope, PA=25°, 115°, 145° and 175° (Hβ region), 2.2m telescope, PA=25° and 115° (Hα region). The spectrum along the companion galaxy (PA=0°) was also obtained with the 2.2m telescope.

In Figure 1a the bar is clearly seen, extending almost all along an axis very close to the disk minor axis. The spiral arms emerge from the bar, with the arm to the north being the more luminous one. The main spiral structure delineates a pseudo-outer ring when the arms close together. The prominent bar structure has a diamond-like aspect (22″×l2″) mainly traced by the two more intense sides. The zones just immediately inside these linear paths are notably fainter, as expected for a region in which the presence of dust is important. The ellipse fitting to the µB=23.5 mag arcsec−2 isophote gives a = 13, b = 12 and PA = 25°. Total (corrected) magnitudes are mB = 12.96(12.65), mV=12.44(12.20) and mI=11.64(11.46).
Minibars in the Centers of Normal Galaxies
Authors: Zasov A. V. , Sil’chenko O. K.
Published: July 2016

Analysis of ionized gas velocity fields in the circumnuclear regions of 13 normal spiral galaxies has shown that about half of them reveal a discrepancy between the kinematical axis at R < 2″ and the photometric or kinematical axes of the outer regions. This result indicates a high frequency of occurrence of non-axisymmetric gravitational potentials in the inner few hundred parsecs of galaxies. The possible nature of these minibars is discussed.
Radio Continuum Maps of Southern Barred Spiral Galaxies
Authors: Mazzolini Margaret , Long Janice , Webster Rachel
Published: July 2016

A sample of southern spiral galaxies are being observed at 20 and 13 cm with the Australia Telescope Compact Array in order to look for examples of anomalous outflows from the nuclear region. In this paper we discuss the radio continuum maps of the three barred spiral galaxies observed to date.
Stellar Dynamics and the 3D Structure of Bars
Authors: Pfenniger D.
Published: July 2016

Recent observational constraints restrict the strict applicability of stellar dynamics in spirals to a few rotation periods. However, stellar dynamics concepts such as periodic orbits are invaluable for understanding the various dynamical processes occurring during much more periods. A distinction of two instability types in stellar systems is pointed out, the first one being well illustrated by the bar instability, and the second one by the bar bending instability. In bars the third dimension brings essential dynamical effects which modify the views about the history of bulges and the spiral secular evolution. Bars may grow, bend, thicken, and dissolve into spheroidal bulges, and spirals may evolve along the Hubble sequence in the sense Sd→Sa. This leads to a much more dynamical picture of isolated galaxies than imagined before.
Ring and Lens Formation
Authors: Combes Françoise
Published: July 2016

The dynamical mechanism to form rings at Lindblad resonances in a barred galaxy is now well-known: due to its dissipative character, the gas is forced in a spiral structure, and experiences torques from the bar potential. Angular momentum is transferred until gas accumulates in the resonant rings. Some problems remain however to account for all observations, such as the very different time-scales for nuclear, inner and outer ring formation, while the three are frequently observed in the same galaxy; the shapes, orientations and thickness of the rings, etc... The adequacy of the present gas dynamical modelizations is discussed.

Lenses are secondary components of barred galaxies that could originate from bar evolution. No model until now has met the observational constraints, in particular the sharp edge of the lenses, their strong velocity anisotropy, and their small thickness. We propose here that lenses are the result of partial bar destruction, a necessary step in a feedback cycle of bar formation-destruction, a cycle driven by gas accretion.
Gas and Shocks in Barred Galaxies
Authors: Teuben Peter
Published: July 2016

A review of the dynamics of the dissipative gas component in barred galaxies is given. The formation of large scale galactic shocks is described, and its implications for star formation and global mass inflow are discussed. Different approaches for modeling the gas will be contrasted, and it will be shown they all produce the same basic morphological picture. However, they do differ in their estimates of mass inflow rates. Some possible directions for future research are indicated.
Dynamical Friction in Barred Galaxies
Authors: Debattista Victor P. , Sellwood J. A.
Published: July 2016

Weinberg’s (1985) perturbative calculation of the dynamical friction by halos on bars predicts that bars will be slowed down very quickly. Previous numerical experiments (e.g. Hernquist & Weinberg 1992) have obtained results that are in agreement with Weinberg’s calculation.

Observations, however, suggest that most bars are rotating rapidly. (In this context, a bar is slow if the major axis Lagrange point is far outside the bar, while a fast bar ends at, or near, this Lagrange point.) Neither Weinberg’s calculation nor the numerical experiments have, to the present date, been fully self-consistent, so possibly important effects such as resonance capture and the back reaction on the bar were not included.
A K-Band Search for Induced Bars in Interacting Systems
Authors: Keel William C. , Byrd Gene G. , Klarić Mario
Published: July 2016

Both active and starburst galactic nuclei are best understood if they are fuelled by gas inflow to the nucleus (e.g. Simkin, Su & Schwarz 1980; Hutchings & Campbell 1983).

There is observational evidence that the occurrence of Seyfert and QSO activity is enhanced in the presence of nearby companions (Dahari 1984; Keel et al 1985; Hummel et al. 1987). At least some samples of Seyfert host galaxies show more close companions than would be expected for a random sample of similar galaxies, though the situation for tidal disturbances themselves is more complex. The selection effects modelled by Byrd et al. (1987) suggest that virtually all the Seyfert galaxies in Dahari’s sample have a companion which is (in principle) physically sufficient to provoke gas inflow in the disk.
Fast and Slow Bars: A Comparative Analysis
Authors: Polyachenko Valerij L.
Published: July 2016

The 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).
Bar-Induced Shocks and the Nature of Regions of Violent Star Formation
Authors: Chernin A. D.
Published: July 2016

Gas dynamics induced by bars involves large-scale shocks. The shock fronts may be curved, especially near the bar edges. Evolution of the curved shocks can lead to effective compression of the interstellar gas which produces favorable conditions for violent star formation in the vicinity of bars.
Counterrotating Bars
Authors: Davies Chad L. , Hunter James H.
Published: July 2016

By including counterrotating angular momentum in two-dimensional galactic disk simulations, we are able to create counterrotating bar modes. Over the period of several dynamical times, the counterrotating inner bar is shown to reverse its pattern direction, oscillate around the primary bar and finally align with it.
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 potential

and a bar potential Φ1(r, θ) = Φb(r)cos(2θ), where

The 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).
Mergers to Bars to Boxy Bulges: A Galaxy Evolution Story
Authors: Walker Ian R. , Mihos J. Christopher , Hernquist Lars , Bolte Michael , de Oliveira Claudia Mendes
Published: July 2016

Deviations from ellipticity in the bulges of edge-on disk galaxies, seen as ”boxy“, ”peanut-shaped“, or “X-shaped“ isophotes, have been known for some time (Jarvis 1986, Whitmore & Bell 1988). Contrary to earlier proposals that these features represent accreted material, recent numerical work (Combes et al. 1990; Raha et al. 1991) suggests that they form when the bars in barred galaxies experience a vertical bending instability and deform out of the disk plane. We have found this latter mechanism at work in simulations in which a bar is induced when a large disk galaxy accretes a small companion galaxy, thus incorporating the mechanism into the evolutionary framework of galaxy interactions. In support of this picture we present observations of Hickson 87a, an edge-on S0 galaxy whose morphological peculiarities exactly match those seen in the simulation.
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

We 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

We 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

It 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

A 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

I 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

The 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.
1.1.1 Space Observations of the Zodiacal Light
Authors: Weinberg J. L.
Published: July 2016

A listing and discussion are given of balloon, rocket, satellite, and space probe observations of the zodiacal light. The paucity of space observations in several critical areas (e.g., in the ultraviolet and near the sun) is noted and suggestions are made for experiments to meet these needs.
1.1.11 The Ultraviolet Scattering Efficiency of Interplanetary Dust Grains
Authors: Lillie Charles F.
Published: July 2016

Surface brightness photometry of the night sky with experiments aboard several rockets and spacecraft indicates a significant enhancement of the brightness of the zodiacal light relative to the sun in the 1700 to 3000 A spectral region. This enhancement is most likely due to Mie scattering by non-absorbing (dielectric) particles with a mean radius of ~0.05µ and a real index of refraction which increases rapidly from ~1.4 to ~2.0 at ~2000 A, where most optical materials have an absorption edge (and exhibit a similar phenomenon). Assuming the visible zodiacal light is produced by 10 to 30µ particles, the number density of 0.5µ particles must be ~3 × 105 times greater, in good agreement with size distributions from crater counts and space probe particle detectors. Ultraviolet observations of comets indicate the enhancement is not due to a bulk property of unmodified cometary dust grains. The most probable source of submicron particles is the breakup of large agglomerates of small (~1000 A) spherical particles like those found by particle collection experiments.
1.2.1 Ground-Based Observations of the Zodiacal Light
Authors: Dumont René
Published: July 2016

At the present time, when spaoe experiments bring us more and more information of increasing quality, it might appear questionable whether ground-based zodiacal light observations are still of interest. Nevertheless, any detailed examination of the available data (see, for example, the review paper of Leinert 1975) shows that a considerable part of our present optical knowledge of interplanetary dust has been contributed by ground-based programmes. Moreover, new available parameters arising from spaoe data, mainly in the field of heliocentric dependence of brightness, open new important abilities for a better interpretation of ground-based observations.
1.2.4 Scattering Layer of Cosmic Dust in the Upper Atmosphere
Authors: Link François
Published: July 2016

The upper atmosphere acts as a giant collector of cosmic dust swept by the Earth on its travel through space. The transient presence of cosmic dust in the upper atmosphere was detected by the rise of the luminance of the twilight sky during the activity of several meteoric showers either by balloon photometers launched by C.N.E.S. at Aire sur l’Adour (Fehrenbach et al., 1972 a) or by the similar photometer at the Pic du Midi Observatory (Link, 1973).
2.1.5 Flux of Hyperbolic Meteoroids
Authors: Dohnanyi J.S.
Published: July 2016

The 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

The 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.
2.2.5 Electrostatic Disruption of Lunar Dust Particles
Authors: Rhee John W.
Published: July 2016

An investigation has been made to study a possibility that dust particles might catastrophically explode on the lunar surface due to electrostatic charging. It is shown that for the dark side along the terminator zone, dust balls and compact stony particles of micron and submicron sizes will be blown up if their surface potential is as low as a kilovolt negative. This mechanism will not operate on the sunlit side because the potential is only 3.5 ~ 20 volts positive. Some of these fragments may possibly levitate in the vicinity of the terminator.
3.1 Dust in Comets and Interplanetary Matter
Authors: Vanýsek Vladimir
Published: July 2016

Results 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.
4.5 Fireballs as an Atmospheric Source of Meteoritic Dust
Authors: Ceplecha Zdeněk
Published: July 2016

This note emphasizes the importance of very bright fireballs as a powerful source of meteoritic dust in the upper atmosphere and on the Earth’s surface. Recently we obtained a direct observational evidence when we photographed the Šumava Fireball, an object of −22 absolute stellar magnitude, on Dec. 4, 1974 at 17h57.5m UT. This is the brightest object on the European Network photographic records during almost 12 years of systematic fireball observations. We obtained 4. all-sky-camera records of the Šumava Fireball from two Czech and one German station of the Network. The most important combination for the trajectory computations proved to be station No. 5 at Ondrejov (Astronomical Institute of the Czechoslovak Academy of Sciences) and station No. 65 at Bernau (Max-Planck-Institut für Kernphysik, Heidelberg). The results are given in Table 1. At Ondřejov we also obtained 4 spectral records of the Šumava Fireball; the most detailed record has a dispersion of 5 Å/mm.
4.6 Interplanetary Dust in the Vicinity of the Earth
Authors: Teptin G.M.
Published: July 2016

The characteristics of the flux density of the interplanetary small particles in the vicinity of the Earth are considered. From the results of the analysis of the characteristics of the suspended dusty particles in the turbulent upper atmosphere the density of flux is obtained. The radar meteor measurements of the turbulent intensity in the upper atmosphere allow to evaluate the flux density of the interplanetary dust as a function of the magnitude of the particles at the intervals of the sizes from ~ 1µ. to ~ 0.05µ. The comparison with the results of different experiments shows a good agreement.
5.2 Dynamics of Interplanetary Dust and Related Topics
Authors: Trulsen Jan
Published: July 2016

The 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

The 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.
5.9 Radiation Pressure on Interplanetary Dust Particles
Authors: Schwehm G.
Published: July 2016

The force acting on an interplanetary dust particle due to solar radiation pressure at a distance R from the sun is given by
5.10 Are Interplanetary Grains Crystalline?
Authors: Drapatz S. , Michel K.W.
Published: July 2016

The 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.
6.2 In Situ Measurements of Dust
Authors: Berg O.E.
Published: July 2016

In this colloquium, my colleagues and I have reported on data from both the lunar surface and from interplanetary space. I am going to comment briefly amd individually on each of these disciplines insofar as they pertain to cosmic dust, but first I would preface those comments with a personal philosophy for each of the two stated disciplines. The two philosophies, you will find, are directly opposite. Concerning the lunar surface, one must recognize that it is a relatively unexplored area for in situ measurements. Accordingly, one must be sufficiently flexible and open-minded to include and consider all available experimental evidence and data until a somewhat consistent model of the lunar surface is derived. Further, and in a similar vein, one’s thinking must not be limited to what little we already know about the lunar surface nor to what is known about the Earth’s surface and terrestrial particles -- assuming that lunar particles are similar to Earth particles. Our lunar experimen shows strong evidence for the electrostatic transport of fines, and yet it is difficult to accommodate that phenomenon on the lunar surface in view of associated parameters that have been derived for the lunar surface, and in terms of what we know about the electrostatic surface properties of terrestrial particulates. But the electrostatic surface properties have been determined in the laboratory on terrestrial particles which are known to have vastly different properties from lunar fines. Thus, it becomes importhat to compile and consider all available data during this early exploration.
6.3 Can Comets be the Only Source Op Interplanetary Dust?
Authors: Delsemme A.H.
Published: July 2016

The steady-state of the meteoritic complex can be achieved by the present input rate of cometary dust, if the long-period and “new” comets release a sizeable fraction of their dust, in grains larger than 100 microns.