bluuebunny/crossref_metadata_2025 huggingface dataset:
Super-Resolution of the Radio Remnant of SN 1987A
Authors: Gaensler B. M. , Tzioumis A. K. , Manchester R. N. , Staveley-Smith L. , Reynolds J. E. , Kesteven M. J.
Published: July 2016

The radio remnant of SN 1987A is now of sufficient flux density that super-resolution is possible at 9 GHz. We present a sequence of images from 1992 to 1996 with a resolution of ≈ 0″.5xb, showing the continuing interaction between the expanding shock front and the surrounding axisymmetric circumstellar material.
Mitaka Correlator for the Space VLBI
Authors: Shibata K. M. , Kameno S. , Inoue M. , Kobayashi H.
Published: July 2016

The Mitaka correlator is an FX-type correlator with 10-station inputs, which is designed for space VLBI and will be used for VSOP mainly. We report here the capabilities of the correlator, the results of model comparisons and the preliminary results of fringe test between the satellite HALCA and Japanese ground telescopes.
HALCA Spacecraft Calibration
Authors: Kobayashi H. , Wajima K. , Murata Y. , Hirabayashi H. , Kameno S. , Kawaguchi N. , Inoue M. , Murphy D. W. ,   the international VSOP team
Published: July 2016

On February 12, 1997 the world’s first dedicated VLBI spacecraft, HALCA, was successfully launched as the space borne element of the VSOP mission. This paper describes the calibration observations that have been undertaken so far with this spacecraft.
Estimation of the Lunar Physical Librations
Authors: Newhall X X , Williams J. G.
Published: July 2016

The recent long-term integration of JPL ephemeris DE403/LE403 yielded lunar physical librations covering 6000 years. A Fourier analysis of a 718-year subset of this span produced estimates of the component frequencies of the forced and free librations. A subsequent iterative least-squares estimation procedure provided precise values for phases and for time-varying amplitudes and frequencies. Two free libration modes were found; presence of a third is possible but close to the noise.
CCD Astrometry of the Solar System
Authors: Arlot J.-E. , Colas F.
Published: July 2016

Astrometry in the solar system made more progress during the past ten years than it did during the seven or eight decades before. In fact, the development of large refractors with micrometers, and after the improvement of the photographic technique, allowed one to get very accurate positions at the end of the 19th century. After that, relatively little progress was made. Astronomers faced several difficulties: first, was the poor sensitivity of the photographic plates leading to long exposures and therefore to low accuracy for faint objects; second, was the poor quality of the catalogues of stars which depended upon a very small number of available astrometric reference stars.

New receptors appeared around the 1950, such as electronic cameras or T.V. tubes. But, most of these new receptors were not interesting for astrometry, mainly because of the field of view – which was too small – and of the difficulty of using such receptors. However, the development of a new technique based upon the CCD targets changed most of the astrometric observational programs. In fact, CCD receptors were made for small fields, but the CCDs were easy to use; the images were numerical, allowing processing by computers, and the sensitivity was much more important. Because of that, the accuracy increased and relative astrometry was developed. The recent development of new catalogues, such as the Guide Star Catalogue and Tycho, permits astronomers to reduce small fields, which was not possible earlier.
Construction of Relativistic Ephemerides and Applications
Authors: Moisson X.
Published: July 2016

The present precision of VLBI observations for the Earth rotation, the accuracy of time measurement realised with modern atomic clocks, and the necessity to obtain precise definition of reference systems and links between them, imply that we compute in the near future more accurate ephemerides, based on general relativity theory (GRT), in accordance with the recent IAU resolutions (IAU, 1992). This paper is dedicated to the presentation of semi-analytical integration of the motion of bodies in the Solar system which completes the theories built at the Bureau des Longitudes by (Bretagnon and Francou, 1988), with some applications in the determination of coordinate time scales links.
Determination of Resonance terms using Optical Observations of Two Meteosat Satellites
Authors: Hugentobler U. , Schildknecht T. , Beutler G.
Published: July 2016

During an observation campaign in winter 94/95 astrometric positions from Meteosat 4 and 5 were acquired at the Zimmerwald observatory using a CCD camera mounted in the prime focus of the 0.5 m Satellite Laser Ranging telescope. The measurements cover a time interval of four months, their precision is of the order of .

The modeling of radiation pressure for the small, cylindrically shaped satellites is relatively easy and they are therefore excellent objects to probe the geopotential. The orbital parameters and the radiation pressure coefficients for the two satellites as well as the resonant coefficients C22, S22 of the geopotential were determined by a single least square adjustment procedure including all the Zimmerwald observations. The relative errors estimated for the terms C22 and S22 are of the order of 1 ÷ 3 · 10−4.
Investigations on Optical and Radio Reference Frames
Authors: Puliaev S. , Andrei A.H.
Published: July 2016

Features of the systematic errors of the Carlsberg Automatic Meridian Circle (CAMC) reference frame are investigated using a secondary radio reference frame defined by a set of astrometric VLA, VLBI and submillimetric positions of radio stars, taken from the literature. The radio positions of 62 stars are compared against the corresponding CAMC positions. The systematic errors of the CAMC catalogue are found to be generally smaller than 005. The radio positions were also compared with the positions obtained with the Bordeaux Automatic Meridian Circle (BORD). It was found a good coincidence between (CAMC–Radio) and (BORD–Radio) systematic differences.
Carlsberg Positions of Planets Compared with JPL DE403
Authors: Morrison L.V. , Buontempo M.E.
Published: July 2016

The Carlsberg meridian telescope has made nearly 20 000 observations of outer Solar System objects since it began operation in 1984. A preliminary version of the Hipparcos catalogue has been used to refer the positions to the International Celestial Reference Frame (ICRF). The observed positions of the major planets are compared with JPL DE403 which is also referred to the ICRF. The agreement with DE403 is good, except for the declination of Jupiter where there is a systematic difference reaching 015 in 1995. The cause of this discrepancy is being investigated at JPL with recent VLBI observations of Galileo.
One - Image Poznań Astrolabe: Project and Prospects
Authors: Kurzyńska K. , Baranowski R. , Dybczyński P. A. , Gabryszewska A. , Lehmann M.
Published: July 2016

A classical astrolabe has been modernised and reconstructed into a new fully automatic instrument equipped with a CCD camera and allowing observations at two different zenith distances: 45° and 60°, respectively. The new instrument permits observations of objects fainter than those observable with the classical instrument. The work on the project is fairly advanced and regular observations are expected to begin in the nearest future. The paper reports results of the first observations and plans for the near future.
Lucien d’Azambuja
Authors: Martres M.J.
Published: July 2016

En 1868, Lockyer et Janssen ont montré qu’il etait possible de faire un relevé journalier de la chromosphère et des protubérances au bord du Soleil en dehors des éclipses totales en utilisant un spectroscope. De 1892 á 1894, H. Deslandres, installé á l’Observatoire de Paris, montra “que la chromosphère entière est décelable dans la demi- sphère tournée vers la Terre” á l’aide d’un petit spectrohéliographe et d’un spectro-enregistreur de vitesses. Avec ces instruments de première génération il obtient des images de la chromosphère de calcium. “L’analyse spectrale et l’application du spectrohéliographe aux raies du spectre solaire ouvre un champ nouveau d’investigation extrêmement vasteȍ ècrit-il. Mai á l’aise á Paris pour développer ses recherches, il s’installe á Meudon. Lá, tout est á faire et il trouve peu de ressources. Il crée un sidérostat et un petit bâtiment pour recevoir les deux petits instruments de Paris, qu’il utilisera jusqu’en 1906. Mais en 1899 il a fait entrer á l’Observatoire de Meudon Lucien d’Azambuja, un jeune homme de 15 ans, soigneux et habile de ses mains pour l’aider dans ses installations et participer aux observations et aux recherches en cours.
A Statistical Investigation of Prominence Fine Structure in the EUV
Authors: Pojoga S. , Nikoghossian A.G. , Mouradian Z.
Published: July 2016

A statistical approach is proposed for the study of the prominence fine structure. Intensity variations in several EUV lines are measured in different regions of prominences. The expected number of fine structural elements is derived.
Magnetic Fields in Filaments
Authors: Démoulin P.
Published: July 2016

Filaments are present in highly non-potential magnetic configurations. On one hand, the complexity of modeling such 3-D configurations makes a useful comparison between observations and models difficult. On the other hand such highly sheared regions are more interesting and challenging for understanding eruptive phenomena like flares and coronal mass ejections. Fortunately, the presence of cold plasma allows us to measure the magnetic field inside prominences. Together with photospheric field measurements and other morphological observations, these provide a large set of puzzling constraints for plausible models of the magnetic configurations. Models are reviewed in the framework of present observational constraints with the aim to clarify a piece of the mystery which surrounds the magnetic configuration of filaments.
Latitudinal Variations of Line-of-Sight Velocity Oscillations in the Photosphere, Chromosphere and Prominences
Authors: Mashnich G.P. , Bashkirtsev V.S.
Published: July 2016

By studying line-of-sight velocity time variations in prominences, we found that velocity oscillations with a period over 40 min have a reasonably well-marked dependence of the period length with heliolatitude. Simultaneous observations of line-of-sight velocities in the photosphere and chromosphere showed that quasi-hourly oscillation periods at these levels in the solar atmosphere and in prominences have a similar latitudinal behavior.
Nonlinear Waves in Force-Free Fibrils
Authors: Zhugzhda Y.D. , Nakariakov V.M.
Published: July 2016

Korteweg-de Vries equations for slow body and torsional weakly nonlinear Alfvén waves in twisted magnetic flux tubes are derived. Slow body solitons appear as a narrowing of the tube in a low β plasma and widening of the tube, when β ≫ 1. Alfvén torsional solitons appear as a widening (β > 1) and narrowing (β < 1) of the tube, where there is a local increase of tube twisting. Two scenarios of nonlinear dissipation of strongly nonlinear waves in twisted flux tubes are proposed.
SUMER/SOHO Filament Observations in Selected Lyman Lines
Authors: Schmieder B. , Kucera T. , Heinzel P. , Vial J.-C.
Published: July 2016

On September 21, 1996 a filament located in a region close to an enhanced network was observed with the SOHO SUMER and CDS instruments. Four Lyman lines have been detected (Lδ, Lϵ, L-6, L-7) by SUMER in the raster mode. We have corrected the spectral data for flatfield and destreching and made wavelength and absolute intensity calibrations. In all these lines we detect a central absorption and an asymmetry in the intensity of the two peaks. Preliminary NLTE computations indicate that these Lyman profiles and their absolute intensities can be reproduced with the existing models provided that we take into account a prominence-corona transition region (PCTR).
Prominence-like Clouds Near HK Aqr
Authors: van den Oord G.H.J. , Byrne P.B. , Eibe M.T.
Published: July 2016

A time series of Hα spectra of the rapidly rotating star HK Aqr has been analyzed. Evidence is found for the presence of cool clouds which are in co-rotation with the star. The cloud velocities, as derived from the clouds’ absorption features, can be used to put constraints on the clouds’ co-latitudes and their distances from the star using a so-called visibility diagram. For HK Aqr most clouds are at distances of 2–3 stellar radii and do not extend beyond the co-rotation radius. By using a simple radiative transfer model, we demonstrate that for most stars the presence of clouds affects the whole Hα profile and does not result in discrete absorptions. Only clouds near rapidly rotating stars, with an inclination close to 90°, will cause discrete absorption features. The cool cloud plasma can form when a temperature inversion is created at the apex of a stellar-sized coronal loop because of reduced coronal heating at large distances from the star. It is likely that the cloud condensations are related to inverse polarity filaments because, near rapidly rotating stars, the axial current in normal polarity filaments decreases with height and has to change sign at the co-rotation radius.
Prominence Eruptions
Authors: Vršnak B.
Published: July 2016

The kinematics and dynamics of prominence eruptions are reviewed and different phases of the eruption are identified. The properties of the equation of motion in these phases are shown. The morphology of the prominence prior and during the eruption is described and the implications to the MHD description of the process are discussed.
The Energetics of Flux-Rope Prominence Models in Axially Symmetric Systems
Authors: Lin J. , Forbes T.G. , Isenberg P.A. , Démoulin P.
Published: July 2016

We analyze a prominence model containing a flux rope which is completely detached from the photosphere. The maximum magnetic energy which can be stored in the configuration does not exceed the open-energy limit proposed by Aly and Sturrock. However, a loss of ideal-MHD equilibrium can occur and create a current sheet which is likely to undergo rapid reconnection.
Prominence Disappearance Related to CMEs
Authors: Hiei E.
Published: July 2016

DB (disparition brusque) events are associated with dynamic phenomena such as a CME, a flare, brightening of a soft X-ray arcade, and soft X-ray dimming, and probably a change of the coronal magnetic field on a large scale. The DB event observed on January 16, 1993 identified with a CME occurred on the solar disk.
CMEs and Prominences and their Evolution Over the Solar Cycle
Authors: Webb David F.
Published: July 2016

Coronal mass ejections (CMEs) are an important aspect of coronal and interplanetary dynamics. They cause large geomagnetic storms and can drive transient interplanetary shocks, which in turn are a key source of energetic particle events. However, our knowledge of the origins and early development of CMEs at the Sun is limited. CMEs are most frequently associated with erupting prominences and long-enduring soft X-ray arcades, but sometimes with no observed surface activity. I review some of the well determined coronal properties of CMEs and what we know about their source regions, with emphasis on the characteristics of the associated prominences and helmet streamers. One of these characteristics is that many CMEs seem to arise from multipolar magnetic structures with multiple or kinked inversion lines. I also discuss the solar-cycle dependencies of these structures, including the role that erupting prominences and CMEs may play in the ejection of magnetic flux and helicity from the Sun.
Disappearances of High-Latitude Filaments as Sources of High-Latitude CMEs
Authors: Oliver E.W. , Webb D.F.
Published: July 2016

From a statistical comparison of high-latitude coronal mass ejections (CMEs) and disappearing solar filaments (DSFs), we find: (1) Beginning with the “rush to the poles”, DSFs arise at an increasing rate from the “emerging” or polar crown relative to the “true” polar crown. At maximum, these “opposite polarity” filaments are the dominant source of high-latitude DSFs. Following polarity reversal, the emergent polar crown becomes the true polar crown and the source of virtually all highlatitude DSFs. (2) At the last two solar maxima, we estimate that there were ~ 4 times as many high-latitude (≥ 60°) CMEs as high-latitude (≥ 45°) DSFs. Possible reasons for this discrepancy include the following: (a) DSFs, particularly small ones, are under-reported, (b) propagation effects, whereby radially propagating CMEs appear at higher latitudes than their underlying source regions, are more important than currently thought, or (c) some combination of these effects.
Time-Latitude Prominence and the Green Corona Distribution Over the Solar Activity Cycle
Authors: Minarovjech M. , Rybanský M. , Rušin V.
Published: July 2016

We present a distribution of prominences over the solar cycle activity. There are found both polar and equatorial branches of prominences that migrate in opposite directions. Prominences of the high-latitude crown migrate, starting in the minimum of the cycle, towards the poles, which they reach at the maximum of the cycle and then decay. The equatorward-migrating branch of prominences appears also in the minimum of the cycle at mid-latitudes and disappears at the end of the cycle. The distribution of the prominences is compared with a time-latitudinal distribution of the green corona. It is assumed that the polar branches in cycle 23 will reach the poles in 2002 (the north pole) and 2003 (the south one), respectively.
A New Station of Prominence Patrol Observations in Slovakia
Authors: Dorotovič I. , Lukáč B. , Pintér T. , Rybanský M.
Published: July 2016

The data from prominence observations provide an opportunity to study spatio-temporal distribution of prominences over a solar cycle. The Slovak Central Observatory (SCO) at Hurbanovo (South Slovakia) in cooperation with the coronal station at Lomnický Štít (Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, Slovakia) constructed a Lyot coronagraph with parameters D/f of 90/1250/3750 mm in 1996 for regular prominence patrol at Hurbanovo (112 m above sea level).

The aim of this collaboration is a joint annual publication of a catalogue of the observed prominences for each year. This paper also describes the form of the catalogue. The authors would appreciate if other observational stations would join this activity. The editor of the catalogue will be the SCO at Hurbanovo.
Precise Radial Velocity Measurements with a Cassegrain Spectrograph, I: Wavelength calibration
Authors: Ilyin I. V. , Duemmler R.
Published: July 2016

We briefly describe the instrumental effects which affect the accuracy of the radial velocity measurements. We have implemented several methods to correct for the instability effects and improve the accuracy of the measurements. These include modifications of the observational strategy and a time-dependent wavelength solution as well as a discussion of the error of the offset from cross-correlation. These methods are applied to observations obtained with the high resolution échelle spectrograph SOFIN mounted at the Cassegrain focus of the alt-azimuth 2.56-m Nordic Optical Telescope, La Palma, Canary Islands.
The Value of Fabry-Perot Interferometry in Studying Long-Term Convective Line Shifts
Authors: McMillan Robert S. , Bressi T. H. , Montani J. L. , Moore T. L. , Perry M. L. , Tubbiolo A. F.
Published: July 2016

Small < 10 m s−1 variations of radial velocity (RV) with multi-year periods in solar-type stars may be indistinguishable from the effects induced on lines by stellar activity cycles (Dravins 1985; Saar & Donahue 1997). Dravins (1992) recommended a resolving power R > 3 × 105 to measure accurately the subtle changes in the shapes of bisectors of photospheric absorption lines driven by changes of granular convection in slowly rotating dwarf stars. Butler et al. (1996) measure impressively small amplitudes of RVs by using echelle spectrographs that cover a broad spectrum. However, to cover a broad spectrum the resolving power is typically limited to < 7 × 104, and the necessary presence of the iodine absorption spectrum may make it difficult to measure convective line shifts contemporaneously with the RV time series. Furthermore, to reach an RV accuracy of ± 3 ms−1 the whole profile of each line is used, thus maximizing the possibility that changes in the shapes of the lines’ C-bisectors could induce an apparent variation of RV.

Dravins (1985) recommended the exclusive use of the steep flanks of photospheric absorption lines to minimize the effects of convection on apparent RV. McMillan et al. (1993, 1994) demonstrated that such RV measurements made with a Fabry-Perot etalon (FPE) interferometer in transmission can be stable in the presence of stellar line variations seen by other investigators whose measurements were not based exclusively on line flanks. Dravins also prescribed high resolving power, high signal-to-noise ratio, high instrumental contrast, and low instrumental wings to analyze the rest of the line profile for convectively-driven changes (Dravins 1978, 1987, 1992). A double- or multiple-pass FPE scanning whole line profiles can provide high R, high contrast, low wings, and a stable, symmetrical line spread function with small (portable) optics, although the low photon efficiency will restrict its use to a few carefully selected stars. The spectral classes of these stars should span the spectral classes of the stars being monitored by others for planets. We describe a possible implementation of this concept that has the potential for adequate photon flux: observing symbiotically through another instrument on a 6-m to 10-m class telescope.
20 Years of CORAVEL Monitoring of Radial-Velocity Standard Stars
Authors: Udry S. , Mayor M. , Maurice E. , Andersen J. , Imbert M. , Lindgren H. , Mermilliod J.-C. , Nordström B. , Prévot L.
Published: July 2016

A preliminary analysis of a sample of more than hundred stars, used as radial-velocity standards and followed with the CORAVEL spectrographs over 1 to 2 decades, is presented. Stars with intrinsic variability or orbital motions are pointed out.
Combining High Angular Resolution Interferometry and Spectroscopy in Studies of Stars and Stellar Systems
Authors: Davis John
Published: July 2016

A number of long baseline optical/infrared interferometers have commenced their scientific programs or are under development. These instruments will provide accurate measurements of the angular sizes of single stars and the angular separations of binary systems at resolutions impossible with conventional telescopes. The combination of interferometric data with the results of high-resolution spectroscopy will, for many classes of objects, provide a powerful method for studying them that neither technique can do alone. Examples include the combination of interferometric and spectroscopic data for spectroscopic binaries and, in particular, for double-lined binaries, and single-lined binaries of known parallax, to determine fundamental stellar quantities. Another example concerns the study of Cepheid variables, where the combination of the data can provide an independent calibration of the zero point of the luminosity scale. The requirements and potential of these combined interferometric-spectroscopic studies are discussed.
Laboratory Determination of the Luminous Efficiency of Meteor Constituents
Authors: Savage Howard F. , Boitnott Charles A.
Published: July 2016

A crossed beam apparatus has been used to measure the emission and ionization cross sections for the prominent spectral features of Na, Ca, Mg, and Fe in collisions with N2 and O2 over the velocity range of 30 to 120 km/s. From the emission and ionization cross sections, the absolute luminous efficiencies in air were determined over the range of meteor velocities. The maximum luminous efficiencies for the brightest features were: greater than 1 percent for the Na D-lines, 0.2 percent for the CaI(2) singlet, 0.06 percent for the MgI(2) and MgI(3) triplets, and O.4 percent for Fe over the visible spectral range. These luminous efficiencies are valid for free molecular flow conditions for velocities above about 30 km/s and are directly applicable to spectroscopic observations of faint meteors. The luminous efficiency of a typical stone will be presented and compared with the efficiencies determined by other investigators. In contrast to previous work, the luminous efficiency found for stone in the present investigation decreases with velocity above about 50 km/s.
The Cosmic Dust Analyzer: Experimental Evaluation of an Impact Ionization Model
Authors: Friichtenicht J. F. , Roy N. L. , Becker D. G.
Published: July 2016

Determination of the elemental composition of cosmic dust particles by means of an impact ionization time-of-flight mass spectrometer has been investigated at several institutions. In most configurations, the instrument supplies the identity of ion groups of both target and particle materials extracted from the impact plasma and the number of ions contained in each group. Experiments have shown that the fractional ionization of a given species is not constant with impact velocity nor is the fractional ionization the same for different kinds of atoms. A model of the impact ionization effect developed at TRW involves an equilibrium plasma condition with the consequence that the fractional ionization for an arbitrary atomic species can be specified by the Saha equation if the plasma volume (V) and temperature (T) are known. It follows that T can be determined by taking the ratio of the Saha equations for two elements present in the target in known concentration. (Taking the ratio negates the requirement of knowing V.) Given T, the procedure can be reversed to yield the relative abundance of elements contained in the impacting particle. To test the model, a PbZrO3-PbTiO3 target was bombarded with high velocity Fe, MoB, and NiAl particles and the number of Pb, Ti, and Zr ions was determined in a time-of-flight mass spectrometer. For each event, the relative abundance of Ti to Pb was taken as known (from electron microprobe analysis) and T was determined from the Ti-Pb measurement. The Zr to Pb ratio was found to be in good agreement with the microprobe analysis (0.38 calculated mean value compared to 0.34 actual). The result was valid for all particle materials and for a velocity range 17<v<47 km/s. T ranged from 3300 to 11 500° K and was only mildly velocity dependent.
Properties of the Magellanic Type Galaxies
Authors: Odewahn S. C.
Published: July 2016

Late-type Magellanic spiral galaxies possess high surface brightness stellar bars whose centers are often offset from the photometric and kinematic disk centers derived from stellar and HI distributions. Since these systems represent the transitional stage between the pure disk and irregular galaxies, and because the spiral arm and bar properties of these systems present many unique aspects, an understanding of their properties will benefit our understanding of the physics underlying the Hubble sequence as well as the mechanisms associated with bar formation. I review detailed photometric and kinematic studies of several important SBm galaxies. Statistical studies using large samples drawn from the Third Reference Catalog of Bright Galaxies support the idea that scenarios invoking the formation of offset bars and/or dominant spiral arms through some tidal interaction mechanism might be attractive, since a common trait among the Magellanic spirals appears to be the presence of a physical neighbor.
Hubble Space Telescope Images of Nuclear Rings in Barred Galaxies
Authors: Barth Aaron J. , Ho Luis C. , Filippenko Alexei V. , Gorjian Varoujan , Malkan Matthew A. , Sargent Wallace L. W.
Published: July 2016

We present new and archival Hubble Space Telescope (HST) images of circumnuclear star-forming rings in barred spiral galaxies. We find that nuclear rings in barred galaxies are composed of large numbers of super star clusters similar to those found recently in other types of starburst systems. In NGC 1097 and NGC 6951, the young clusters have absolute magnitudes of up to Mv = −14 or −15, depending on highly uncertain extinction corrections, and effective radii of 2–3 pc. The images (especially that of NGC 6951) also show intricate spiral dust lane structure interior to the rings.
HI Observations of Barred Magellanic Type Galaxies
Authors: Wilcots Eric M. , Lehman Cathy , Miller Bryan
Published: July 2016

We present the results of a VLA D-configuration survey of a sample of Barred Magellanic type (SBm/IBm) galaxies. The data show that: (1) the HI is extended well beyond the optical diameter; (2) the HI distribution often has a different position angle than the optical distribution; (3) the bar morphology is typically manifested in the HI kinematics; (4) these galaxies not only tend to have gaseous companions, but they also tend to be strongly interacting systems; and (5) the companions have no obvious optical counterparts.
Morphology of Dust Lanes in Bars
Authors: Regan Michael W. , Vogel Stuart N.
Published: July 2016

Given that dust and molecular gas tend to concentrate at the locations of either shocks or orbit crowding, the study of the dust morphology of barred spirals can give insight into the kinematics of the galaxies. In order to do this, we present a sample of barred galaxies for which we have obtained near infrared and optical photometry and BIMA interferometer observations of CO emission. We obtain the dust extinction and relative scale height of the dust and stars using a radiative transfer model to interpret the photometry. We find that the scale height of the stars compared to the dust is generally larger in the central regions compared to further out in the bar dust lanes. The morphology of the dust extinction regions closely resembles the distribution of CO emission. An analysis of a larger sample of galaxies with IR data indicates that dust column densities appear larger in the nuclear regions than in the bar dust lanes. The sample also shows that the distribution of dust is not symmetrical along the bar with one side of the bar usually having a larger column density of dust than the other side.
The Pattern Speed of NGC 936 by the Tremaine-Weinberg Method
Authors: Kuijken Konrad , Merrifield Michael R.
Published: July 2016

We describe a kinematic measurement of the pattern speed in the classic SB0 galaxy NGC 936. While the practicalities of this method remain difficult, allowance for non-Gaussian velocity distributions enables more reliable measurements than hitherto possible. The bar of NGC 936 appears to end just inside its corotation radius.
CO in NGC 4314: The Detection of Inflow Along the Bar
Authors: Benedict G. Fritz , Smith Beverly J. , Kenney J. D. P.
Published: July 2016

We present CO(1-0) interferometer data with × spatial resolution and 13 km s−1 velocity resolution acquired at the Owens Valley Radio Observatory. These data reveal a clumpy circumnuclear ring of gas. We also find a central peak of CO within 2″ of the optical center. Deviations from circular motion are seen where the dust lanes along the leading edge of the bar intersect the nuclear ring, consistent with gas inflow along the bar. Hα maps of this galaxy show bright HII regions near the ends of this inflow region, indicating triggering of star formation by the inflow.
Gas Dynamics and Active Phenomena in Galactic Nuclei: M100 and M94
Authors: Sakamoto Kazushi , Minezaki Takeo , Wada Keiichi , Okumura Sachiko , Kobayashi Yukiyasu
Published: July 2016

Since molecular gas fuels AGNs and molecular clouds form stars, understanding of molecular gas dynamics is a key to the understanding of active phenomena (such as starbursts and AGNs) in galactic nuclei. To study gas dynamics in weakly barred galaxies, we made CO interferometry (to trace gas) and NIR imaging (to trace stars) toward two nearby SAB galaxies M100 and M94. Each galaxy has a small stellar nuclear bar and also has an outer bar or oval distortion, thus suitable for the study of gas dynamics in a barred gravitational potential. Observations were made using Nobeyama Millimeter Array (NMA) and the IRcamera PICNIC installed at the ISAS 1.3 m telescope.
Bar Formation, Evolution and Destruction
Authors: Sellwood J. A.
Published: July 2016

I review the various mechanisms for creating bars in rotating stellar disks, and conclude that the swing-amplified feed-back loop, which produces rapidly tumbling bars, remains the most probable. The bar continues to evolve after its formation in a number of ways; here I discuss what appears to be inevitable thickening normal to the plane, continued spiral activity in the outer disk and also underscore the increasingly important problem presented by angular momentum loss to the halo. Finally, I examine possible means, excluding interaction, by which bars in galaxies could be destroyed.
Evolution of Bars in Isolated and in Interacting Disk Galaxies
Authors: Athanassoula E.
Published: July 2016

I use N-body simulations to follow the evolution of bars in both isolated and interacting disk galaxies. The pattern speeds of bars evolving in isolated galaxies decline gradually with time, due to transfer of angular momentum from the bar to other components in the galaxy. Both the form and amount of this decline depend on the model used. The fate of a bar in an interacting disk galaxy depends on the mass, central concentration and orbit of the perturber. The pattern speed, form and amplitude of the bar may change, the bar can become off-centered, or, more drastically, it can disappear altogether. Finally I propose a scenario for the evolution of NGC 7217, which could, if proven correct, explain the formation of the rings in that galaxy and also, at least qualitatively, the existence of a retrograde population.
Non-Linear Excitation of Warps by Spiral Waves in Galaxies
Authors: Masset F. , Tagger M.
Published: July 2016

We present a mechanism to explain the permanent excitation of warps in spiral or barred galaxies. We show that non-linear mode coupling with the spiral wave can be very efficient to drive two warp waves. We derive an expression of the coupling coefficient in the WKB approximation. We show that the coupling is too weak in the stellar disk, except at the Outer Lindblad Resonance where the spiral slows down and is efficiently coupled to warp waves. There, the spiral can almost completely transfer its energy and angular momentum to a ”transmitted“ warp, which we can observe in HI, and a ”reflected“ one, which we can observe as a corrugation. Our mechanism reproduces the observed amplitudes of the warp and of the corrugation.

We first present side results concerning the propagation of warps in moderately thick disks.
The Florida Barred Galaxy Program
Authors: Hunter J. H. , Gottesman S. T.
Published: July 2016

For more than a decade, a group at the University of Florida has been constructing models of barred spiral galaxies that we have observed at the VLA. Group members include: S. T. Gottesman, G. Contopoulos, J. H. Hunter, several Ph.D. students, and collaborators at other institutions. The HI distributions in our galaxies are either gas rich, or nearly devoid of gas, in their bar regions. Initially, we deduced density distributions and potentials of the stellar disks and bars from near infrared observations, modeled the gas response assuming different pattern speeds, etc., and compared the models with our HI observations. This simple approach is successful in some cases, such as NGC 3359, but less successful in others. More recently, our approach has been toward selfconsistent models, including stars and gas. Our techniques range from the Contopoulos-Grosbøl-Kaufmann stellar dynamical approach to methods exploiting grid codes and SPH tree codes. Some of our observations and models will be reviewed, and some new results will be presented.
Stellar Orbits in Doubly-Barred Galaxies
Authors: Hasan H.
Published: July 2016

The question of bars within bars has been reviewed by Friedli and Martinet (1993), who have also performed N-body simulations to produce nested bars. They propose that if a system of embedded bars is effective in transporting gas to the galactic center (Shlosman et al. 1989), then it is perhaps a step in the secular evolution of barred galaxies. In order to pursue this interesting proposition, and also because observational evidence for the existence of secondary bars is mounting (e.g. Buta & Crocker 1993; Shaw et al. 1993, Wozniak et al. 1995), it is important to understand the stellar kinematics in such systems.
The 65 cm PZT of the U. S. Naval Observatory
Authors: Klepczyński W. J.
Published: July 2016

The Time Service Division of the U.S. Naval Observatory has undertaken a program to construct and install at Washington, D. C. (latitude +39°) a 65 cm photographic zenith tube (PZT) telescope to be used in studies pertaining to the rotation of the Earth. It is expected to improve the precision with which the rate of rotation of the variation of latitude can be determined by photographic techniques and, in addition, will make possible more frequent determinations of these qualities. Due to itp larger field of view, direct intercomparison with the results obtained with other instruments near latitude, +39° will be feasible. Also, it is expected to contribute to studies of the proper motions of stars near declination +39°.
Note on Selection of Coordinate Systems for Geodynamics
Authors: Henriksen S.
Published: July 2016

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.
1.1.10. Evidence for Scattering Particles in Meteor Streams
Authors: Levasseur Anny-Chantal , Blamont Jacques
Published: July 2016

From observations made with a photometer placed on board D2A-Tournesol from April 1971 to June 1973 at ε = ± 90° for all ecliptic latitudes, we had deduced that the intensity of the zodiacal light is not constant, but shows fluctuations, some of which we correlated with cometary debris. The measurements were carried out by scanning the celestial sphere in a plane orthogonal to the Sun-Earth direction with a one minute period (LEVASSEUR et BLAMONT, 1973). BURNETT, SPARROW and NEY (1974) have pointed out that our data could have been contaminated by stray moonlight; we have therefore refined our data analysis and conclude that indeed fluctuations of the intensity of the zodiacal light do exist, even when the Moon is much below the horizon.
1.1.19 Visible and UV Photometry of the Gegenschein and the Milky Way
Authors: Llebaria A.
Published: July 2016

The French astronomical satellite D2B is to be launched on September 1975. The spin axis is constantly oriented towards the sun with an accuracy of ± 30 arc min. The ERC experiment (field recognition) wii provide imager in three spectral intervals of a region centered at the anti-sun point and having a diameter of 10°. The scanning of this region is realized by a combination of the spin motion of the satellite and internal electronic scanning. This experiment includes a catadioptric objective [optimized Kern telescope) with a field of 3° × 6° and an image dissector which analyses the image.
2.2.4 Lunar Soil Movement Registered by the Apollo 17 Cosmic Dust Experiment
Authors: Berg Otto E. , Wolf Henry , Rhee John
Published: July 2016

In December, 1973, a Lunar Ejecta and Meteorites (LEAM) experiment was placed in the Taurus-Littrow area of the moon by the Apollo 17 Astronauts. Objectives of the experiment were centered around measurements of impact parameters of cosmic dust on the lunar surface. During preliminary attempts to analyze the data it became evident that the events registered by the sensors could not be attributed to cosmic dust but could only be identified with the lunar surface and the local sun angle. The nature of these data coupled with post-flight studies of instrument characteristics, have led to a conclusion that the LEAM experiment is responding primarily to a flux of highly charged, slowly moving lunar surface fines. Undoubtedly concealed in these data is the normal impact activity from cosmic dust and probably lunar ejecta, as well. This paper is based on the recognition that the bulk of events registered by the LEAM experiment are not signatures of hypervelocity cosmic dust particles, as expected, but are induced signatures of electrostatically charged and transported lunar fines.
2.3.2 Analysis of Impact Craters from the S-149 Skylab Experiment
Authors: Hallgren D.S. , Hemenway C.L.
Published: July 2016

Analysis of craters found on polished plates exposed during Skylab has provided data for a flux measurement over the mass range 10−15 to 10−7 gms. Chemical analysis of residues in the craters shows a high incidence of aluminium. A variety of morphological forms are described.
4.4 The Heliocentric Distribution of the Meteor Bodies at the Vicinity of the Earth’S Orbit
Authors: Andreev V.V. , Belkovich O.I. , Tokhtas’ev V.S.
Published: July 2016

A determination of velocity distributions of sporadic meteor bodies and distributions of their radiants over the celestial sphere corrected for the motion and attraction of the earth is one of the main problem of the meteor astronomy. An analytical model of these distributions has certain interest.
4.8 Evolution and Detectability of Interplanetary Dust Streams
Authors: Kresák Lubor
Published: July 2016

Sudden enhancements in responses recorded by micrometeoroid detectors flown on spacecrafts have been repeatedly attributed to encounters with streams of cometary debris similar to, or identical with, the meteor streams known from ground-based observations. Por measurements made in the Earth-Moon environment, spacecraft effects, atmospheric fragmentation of larger particles, and possibly lunar ejecta can be misinterpreted as interplanetary streams. For deep space observations it is necessary to inquire whether a compact dust stream can persist under the dispersive and destructive effects which increase rapidly with decreasing particle size.
5.5 Temperature Distribution and Lifetime of Interplanetary Ice Grains
Authors: Lamy Ph. , Jousselme M.F.
Published: July 2016

An improved solution of the temperature distribution of interplanetary ice grains is presented using the refractive index measured at 100° K. The efficiency factors for absorption are obtained from Mie theory and the calculation is carried out for micronic and submicronic grains at 50, 100 and 150° K; corresponding lifetimes are given.
5.7 Rotational Bursting of Interplanetary Dust Particles
Authors: Paddack Stephen J. , Rhee John W.
Published: July 2016

Solar radiation pressure can cause rotational bursting and eventual elimination from the solar system of small asymmetric interplanetary particles by a windmill effect. The life span determined by this process for stony meteoritic material or tektite glass with radii of 1 cm is on the order of 105 years. Same size material which contains iron, nickel or aluminum, with properties such that it is subject to 5 percent of the amount of spin damping as pure metals, can be removed from the solar system on the order of 106 years by this process. Ordinary chondritic material, despite its high resistivity, is subject to a type of magnetic spin damping, in addition to the normal spin damping, with the consequent result that this type material cannot be removed from the solar system by this process. This depletion mechanism appears to work faster than the traditional Poynting-Robertson effect by approximately two orders of magnitude for the nonmetallic particles and one order of magnitude for the metallic particles.
6.5 Final Remarks
Authors: Whipple F.L.
Published: July 2016

My summary will certainly leave out much fine work but will stress a few of the points that impressed me.

First, I note remarkable progress since 1967 when I last worried about the interplanetary complex, particularly the new observations from space and of very small particles. I am delighted to see the ground based Zodiacal Light observers, like Weinberg and Dumont, converging on their observations both of polarization and of intensity. The larger particles are clearly the major contributors particularly away from the Sun. This forces the theoreticians and the laboratory people to find out how these larger particles produce the observed polarization including the negative polarization. Theoreticians always can prove the answer when it is known.
Some Thoughts on Multiple Stars
Authors: Evans David S.
Published: July 2016

The occultation and spectroscopic approaches to the discovery of multiple stars are reviewed, and the technique of spectroscopic measurement recapitulated. A notation for multiple stars is proposed. An examination of the gravitational interaction levels suggests an average value of ∆ log P for one hierarchical step close to 3.0 and ∆ log a near 2.0 consistent with a binding ratio near 1 : 10000. The distribution for B stars seems to differ from other types and it is conjectured that they cannot be old enough to be residues of clusters. In general few multiple systems seems to show evidence of age sufficient for advanced evolution of the components.
Statistical Properties of Trapezium Systems
Authors: Allen Christine , Tapia Mauricio , Parrao Laura
Published: July 2016

A catalogue of more than 900 multiple systems of trapezium type has recently been completed. In constructing the catalogue an attempt was made to exclude optical systems. We study the galactic distribution of trapezia of different spectral types, and we compare it with that of ordinary multiple systems and of visual binaries from the IDS. An estimate is made of the expected number of pseudo-trapezia among each spectral type. This study shows that most of our trapezia are true trapezia and should therefore be young. This conclusion holds for trapezia of all spectral types.
Stable Orbits in the Circular Plane Restricted Three-Body Problem
Authors: Benest Daniel
Published: July 2016

We investigate by numerical exploration the extended regions of stability for retrograde satellites when the mass of the less massive body increases up to μ = 0.5. A preliminary study is made of the characteristic and stability properties of the families of periodic orbits; then the general case of non-periodic orbits is considered. Those numerical explorations show that for stable large non-periodic orbits, the motion can be decomposed into a fast “reference motion” and slow libration; we study theoretically this libration in Hill’s case for which the “reference motion” is elliptic.