bluuebunny/crossref_metadata_2025 huggingface dataset:
Global Pattern of the Magnetic Field Vector Above Neutral Lines from 1974 to 1982: Pic-du-Midi Observations of Prominences
Authors: Bommier V. , Leroy J.L.
Published: July 2016

The magnetic field vectors derived from the Hanle effect measured in prominences during the ascending phase and maximum of Cycle 21 have been plotted on the corresponding synoptic maps of Meudon Observatory (e.g., Figure 2). Most of these measurements have been performed in a single line, He I D3. Our previous analysis of 2-line measurements have already proven that prominence magnetic fields have Inverse polarity (Bommier et al. 1994) and remain close to the horizontal plane (Bommier et al. 1986, 1994). We also found earlier that the field component along the filament axis shows a remarkable large scale pattern, especially at high latitudes (Leroy et al. 1983). Given the geometry of horizontal Inverse field, we reinvestigate this large scale organization through our complete set of observations (296 prominences). These new maps fully confirm and extend to medium latitudes the law of reversal of the axial field from one prominence band to the adjacent ones (see Figure 2). This behavior, together with the Inverse polarity pattern, gives a picture consistent with a North-South global field distorted by the differential rotation (see Figure 3).
A New Multichannel Fourier Transform Spectrometer
Authors: Nordgren Tyler E. , Hajian Arsen R.
Published: July 2016

Stellar spectra have been obtained using a multichannel Fourier Transform Spectrometer (FTS) which incorporates components of the Navy Prototype Optical Interferometer. It is well known that a FTS can provide superior wavelength stability as compared to traditional spectrometers. Unfortunately the FTS traditionally suffers from exceptionally poor sensitivity, which until now has limited its uses to sources with high fluxes and/or those with narrow band emission (e.g. the Sun, nebulae, and laboratory samples). We present stellar observations using a new FTS design which overcomes this sensitivity limitation by using a conventional multichannel spectrometer in conjunction with the FTS system. The signal-to-noise ratio of spectra from our test-bed observations are consistent with the theoretical prediction and show that for N channels the sensitivity scales like N, while the signal-to-noise ratio scales like . With this type of an instrument on a 3-m telescope and 9 000 channels we expect to be able to detect and measure such exciting astrophysical phenomenon as gravitational redshifts from single, main sequence stars and extrasolar planets of terrestrial mass.
Using the Radial Velocity Spectrometer at the Dominion Astrophysical Observatory
Authors: Skuljan J. , Hearnshaw J. B. , Cottrell P. L.
Published: July 2016

Two observing runs have been undertaken at the Dominion Astrophysical Observatory (DAO) using the radial velocity spectrometer (RVS). About 800 observations have been performed with both the K and F masks. All cross-correlation profiles have been divided by the corresponding flux monitor records and full gaussian functions have been fitted in order to determine the profile centers. A number of IAU standard radial velocity stars have been observed, with a typical internal precision for a given star of about 100 m s−1, which is a factor of two or three better than the usually adopted value for the RVS. Zero-point offsets between these observations and the standard values were also investigated.
Minimizing Radial-velocity Errors caused by Spectral-type Mismatch in Early-type Stars
Authors: Verschueren Werner , David Marc , Vrancken Myriam
Published: July 2016

We present the first results of a long-term study to increase the external accuracy of (relative and absolute) radial velocities of early-type stars below the 1 km/s level. The accuracy suffers mainly from important systematic errors caused by intrinsic object-template mismatch in cross-correlation. Based on synthetic spectra, the magnitude of these mismatch errors is shown in different spectral regions and for different rotational velocities around spectral-type mid-A. A line selection and combination scheme is proposed which optimizes the accuracy (systematic errors) in view of the precision (random errors) required.
Importance of Precise Radial Velocities for Cepheid Binaries
Authors: Szabados L.
Published: July 2016

In view of the high incidence of duplicity among Cepheids, a large number of binary systems remain to be discovered because of the low amplitude of the orbital effect superimposed on the radial velocity variation due to radial pulsation. This fact is shown by simple statistics. The importance of combining astrometric data with radial velocity measurements is also emphasized. Finally the systematics of the radial velocity amplitude as a function of the pulsation period is considered for classical Cepheids.
Towards a New Set of High-Precision Radial-Velocity Standard Stars
Authors: Udry S. , Mayor M. , Queloz D.
Published: July 2016

20 years of CORAVEL photoelectric radial-velocity measurements associated with the high precision achieved by the ELODIE spectrograph on a fair time span allow us to propose a new list of high-precision radial-velocity standards with velocity variations lower than a few times 10 m s−1.
Combined Observations of Meteors by Image-Orthicon Television Camera and Multi-Station Radar
Authors: Cook A. F. , Forti G. , McCrosky R. E. , Posen A. , Southworth R. B. , Williams J. T.
Published: July 2016

Observations from Multiple Sites of a radar network and by television of 29 individual meteors from February 1969 through June 1970 are reported. The primary purpose of the program was to compare ionization with luminosity. Only 12 of the meteors did not appear to fragment over all the observed portion of their trajectories. From these 12, the following relation for the radar magnitude MR to the panchromatic absolute magnitude Mp, in terms of velocity of the meteor V, was found:
NASA-LRC Faint Meteor Spectra
Authors: Harvey Gale A.
Published: July 2016

A brief description is given of the instrumentation, the facilities, and the patrol technique used by the NASA Langley Research Center Faint Meteor Spectra Patrol. A classification of 500 meteor spectra obtained in the first 2-1/2 years of the patrol is given. The general characteristics of “typical” spectra are discussed and preliminary conclusions drawn. Examples of unusual spectra are briefly described.
Motion of a Fragment in Disturbed Air Behind a Meteor Body
Authors: Padevět V.
Published: July 2016

Even if we use the classical physical theory of meteors, there may still be some possibility for agreement between observations and theory. The effect of disturbed air behind the main body on the motion and ablation of fragments has not yet been considered. This effect may have important consequences, observed partly as the difference between the photometrically and the dynamically determined masses of the meteor body. By use of extreme mathematical conditions, this difference can be made to reach orders of magnitude during the latter part of the trajectory. However, the physical interpretation is considered only roughly in this paper, and the computed model needs further improvement. But the main purpose here—finding an important effect for the explanation of the discrepancy between the dynamic and the photometric masses, especially for large bodies—has been achieved.
Dust Storms in Space?
Authors: Roosen Robert G. , Berg Otto E. , Farlow Neil H.
Published: July 2016

Silverberg (1970) has explained the “dust storms” observed by the early satellite-borne microphone detectors by postulating that the orbital planes of short-period, low-inclination comets are filled with micrometeoroids. We report here on three separate approaches to test the validity of this hypothesis.

(1)

Optical scans of the Gegenschein brightness can yield no useful information on the nearly isotropic sheets of dust predicted by Silverberg.

(2)

An attempt to directly collect dust particles during a predicted high flux period by means of a sounding rocket yielded negative results.

(3)

Over three years of particle impact data from extremely sensitive detectors flown aboard Pioneers 8 and 9 show no observable dust storms.

Hence Silverberg’s hypothesis appears untenable.

However, we should not rule out the possibility that observable showers of very small particles can be blown directly off the nuclei of some comets passing between the Earth and the Sun.
Accumulation of Chondrules on Asteroids (Abstract)
Authors: Whipple Fred L.
Published: July 2016

It is shown that aerodynamic forces could have played a significant role in the selective accumulation of chondrules on asteroids that are moving with respect to the gas in a primeval solar nebula. Particles smaller than millimeter chondrules would sweep by an asteroid moving more slowly than a critical velocity, while larger particles could be accumulated by impact. Theory and calculation cover the case of subsonic velocity and asteroidal diameter up to 50 km independent of the nebular density from 10-8 to 10-6 g cm-3 or higher for smaller asteroids, as illustrated in table 1.

The calculations are based on a solar mixture of materials at T = 550° K and on Stokes’ law of aerodynamic drag, which fails for nebular densities below about 10-8 g cm-3 for millimeter sized spheres. Below this limit the limiting velocity falls off proportionally to gas density. Note that the accretion rates for small particles can be severely restricted because of aerodynamic flow at small asteroidal velocities with respect to the gas. Near and above the critical velocity the asteroidal gravity does not materially add to the accretion rate regardless of asteroidal mass.
The Early Evolution of the Solar System
Authors: Cameron A. G. W.
Published: July 2016

The problems of relating collapse conditions in an interstellar cloud to a model of the primitive solar nebula are discussed. In such a nebula there is a radial force balance between gravity, the pressure gradient, and centrifugal forces due to the rotation. Approximate values are given for the combinations of temperature and density throughout the nebula, from a maximum of about 2000° K near the center to less than 200° K in the outer portion. These conditions are based upon the compression adiabats in the terminal stages of the collapse of an interstellar cloud. One general conclusion, of great importance for accumulation of bodies within the solar system, is that interstellar grains should not be completely evaporated at distances in the nebula beyond about one or two astronomical units.
The Morphology of Barred Galaxies
Authors: Buta Ronald
Published: July 2016

In this review, the morphology of barred galaxies at optical wavelengths is discussed, focussing mainly on early to intermediate revised Hubble types in the range S0+ to Sbc. Previous work by Hubble, Sandage, de Vaucouleurs, Vorontsov-Velyaminov, and Kormendy is described. The primary emphasis is on ring phenomena, and morphological results from the Catalog of Southern Ringed Galaxies are summarized.
Star Formation in Barred Galaxies
Authors: Phillips Andrew C.
Published: July 2016

Star formation in barred spirals is discussed, including star formation rates, distribution of H ɪ regions, and H ɪ region luminosity functions. In general, global star formation rates and other properties are consistent with non-barred spirals of comparable Hubble class. In barred spirals of intermediate class (SBb-SBc), the effects of the bar on star formation is clearly seen in the distribution of star forming sites. Two patterns emerge, one that shows star formation concentrated in ring-like zones corresponding to inner and nuclear rings (earlier types) and one that shows star formation concentrated in the bar itself (later types). These properties appear to be well-correlated with both Hubble stage and bar type.
Properties of H ɪɪ Regions Along Galactic Bars
Authors: Martin P.
Published: July 2016

A study of general properties of H ɪɪ regions along the bars of 11 spiral galaxies is presented. From Hα imaging, distributions, morphology and star formation rates are established. Physical conditions derived from spectrophotometry reveal that strong shocks are absent in H ɪɪ regions along bars and electron densities appear to be normal. Abundance distributions indicate that mixing of the ISM is taking place along bars.
Multicolor Photometry of Barred Spiral Galaxies
Authors: Horst William D. , Peterson Charles J.
Published: July 2016

B – V and R – I color maps (from CCD imagery obtained at Cerro Tololo Inter-American Observatory) of six barred spiral galaxies have been used (Horst 1992) to investigate stellar populations within the bars and nuclei. Two-color diagrams show that the distribution of pixel colors largely parallels the expected locus for normal unreddened stars. If the “reddening” law is assumed to remain fairly constant, and if the slope of the vector associated with this reddening law is additionally assumed to be commensurate with that derived from models which take into account both absorption and scattering (Witt et al. 1992), one concludes that the overall effects of internal extinction are remarkably uniform along the bars and within the nuclei of all six galaxies. It thus appears reasonable as a first approximation to shift the observed data along the assumed reddening vector to estimate the spectral types of stars that are present and to investigate differences between bar and bulge populations. Nevertheless, to correct surface brightness distributions for the effects of internal extinction, and hence to proceed with more detailed attempts to model the various luminosity components (i. e., the bulge, bar, etc.), is a complex problem which must be addressed through numerical models explicitly designed to reproduced barred systems.
Star Formation Along the Bars of Virgo Cluster and Isolated Spiral Galaxies
Authors: Koopmann Rebecca A. , Kenney Jeffrey D. P.
Published: July 2016

Star formation along the bar is common in late-type barred galaxies (Phillips and Garcia-Barreto et al., these proceedings), which tend to have weak stellar bars. It is rarer in strongly barred galaxies, e.g., early-type spiral galaxies. Abundance gradient measurements (Martin & Roy 1995) and simulations (Friedli & Benz 1995) suggest that star formation along the bar of strongly barred galaxies may indicate a young bar. Since bars can be created in tidal interactions and mergers (Noguchi 1987), it is of interest to investigate the star formation properties of barred galaxies in different environments. We use Hα images to compare the star formation properties in the bar region of a sample of barred galaxies in the Virgo Cluster and a control sample of isolated galaxies. We focus on the three galaxies with the strongest star formation along the bar, including NGC 4424, a possible merger remnant.
Multiband Photometry of NGC 7479 and NGC 7606
Authors: Varela A. M. , Aguerri J. A. L. , Prieto M. , Muñoz-Tuñón C.
Published: July 2016

We present surface photometry in U BV RI passbands of the barred spiral galaxies NGC 7479 and NGC 7606, for which observations were obtained at the Cassegrain focus of the 2.5-m Isaac Newton Telescope at La Palma. Data are presented in the form of images and mean radial profiles from azimuthal fits of ellipses, giving the luminosity, ellipticities and position angles of the isophotes as functions of the galactocentric radii. Images in I-band are shown in Figure 1 of NGC 7479 (left) and NGC 7606 (right). These belong to a sample of galaxies with moderate circumnuclear starbursts. We are analyzing their structure to study the effects of departures from an axisymmetric potential for the dynamics of a galaxy. One objective of this study is to make a three-dimensional model of the bar and bulge using the method of photometric inversion. The sample consists of 27 spiral galaxies with and without a bar.
The Effect of Bars on the Fueling of Star Formation and Nonstellar Activity in Galaxy Nuclei
Authors: Ho Luis C. , Filippenko Alexei V. , Sargent Wallace L. W.
Published: July 2016

Theoretical studies suggest that large-scale stellar bars can be highly effective in delivering gas to the central few hundred parsecs of a spiral galaxy, which may then initiate rapid star formation. Further instabilities may lead to additional inflow to physical scales relevant for active galactic nuclei. We test these predictions in light of recent observations. Compared to unbarred spirals, barred galaxies of type S0-Sbc have a higher probability of exhibiting nuclear star formation, as well as a higher formation rate of massive stars; neither effect is present in spirals of later morphological type. Bars, on the other hand, do not have an obvious influence on active nuclei. We discuss the implications of these findings for the fueling of central star formation and active nuclei.
Pattern Speeds in Barred Galaxies
Authors: Elmegreen B.
Published: July 2016

The ratio R of the corotation radius to the bar radius ranges from 1 to 1.8 in theoretical models that fit the observed dynamics of gas or stars in the bar and spiral regions of galaxies. Most models cluster around a ratio R = 1.2 for early type galaxies. This ratio confirms the bar-aligned orbit theory long held by Contopoulos and others, which requires that R < 1, but it also suggests that bars do not end exactly at corotation, as is often assumed, but significantly inside. The difference between R = 1 in the old interpretation and R = 1.2 or 1.4 in the fitted models is critical for our interpretation of bar-spiral morphologies. It appears that the bar-to-spiral transition in early Hubble types occurs between the inner 4:1 resonance and corotation, in the range corresponding to R = 1.55 to 1 for a flat rotation curve, because of orbit stochasticity where the 2m: 1 orbits in the x1 family cluster together in space. Corotation then occurs relatively far out in the arms, at an angle from the bar end that may exceed 60° for tightly wrapped spirals. This position sometimes corresponds to the crossing of a dust lane from inside the arms to outside (NGC 1300, NGC 1365) or to a spiral arm bifurcation as in non-barred galaxies. The relatively high value of R is also consistent with the identification of inner rings with the inner 4:1 resonance, outer rings with the outer Lindblad resonance, and offset bar dust lanes and nuclear rings with the inner Lindblad resonance. In contrast to this clear interpretation for early type galaxies, there is little consensus on the location of corotation in late type galaxies, which usually lack an inner Lindblad resonance interior to the bar. It is also not known whether late type spirals corotate with their bars, although this appears to be the case for early type galaxies based on the ubiquity and location of outer spirals and rings.
The presence of a Bar—Like Structure in the Central Regions of Seyfert Galaxies
Authors: Afanasiev V. L. , Shapovalova A. I.
Published: July 2016

The central (8″ × 8″) regions of the Seyfert galaxies Mrk 744 and NGC 4151 were studied by the 3D-spectroscopy method. There is evidence that a mini-bar (0.5–2 kpc) is present in the central regions of these galaxies, which provides transportation of gas of the disk to fuel the nucleus.
Box/Peanut Galaxies in the Near-IR
Authors: Baggett S. M. , MacKenty J. W.
Published: July 2016

Galaxies with box/peanut-shaped (b/p) bulges have been known for some time (e.g., NGC 128 and NGC 7332 (Sandage 1961)). Observationally, b/p features are detected in edge-on systems, and are visible in images, contour maps, and brightness profiles as isophote sections that near minor axis are relatively flat and parallel to major axis (see Figure 1). Peanut-type bulges have isophotes indented at the intersection with the minor axis.

There have been several morphological surveys to date. The two most recent studies have found that about 20% of early-type galaxies and nearly 45% of all disk galaxies are b/p galaxies (see Shaw 1987, Dettmar 1989, and references therein) and that the b/p galaxy properties appear similar to normal spirals in the optical, radio, and infrared. A few kinematical studies have been done: b/p bulges are found to rotate more like disks than bulges (e.g., 150 km s−1up to 6 kpc above the plane in NGC 128 (Jarvis 1990) and the velocities remain constant up to large z, implying cylindrical rotation (e.g., NGC 3079 has v constant out to 1.6 kpc (Shaw et al. 1993)).
Neutral Hydrogen in the Bar of NGC 4151
Authors: Mundell C. G. , Pedlar A. , Shone D. L. , Asif M. W. , Robinson A. , Axon D. J.
Published: July 2016

Bars are thought to play a crucial role in the fueling of AGN (see e.g., Mundell et al., in these proceedings and references therein), and as part of a project to investigate this, we have studied the neutral hydrogen structure in the bar of the Seyfert 1.5 galaxy NGC 4151.

High-sensitivity VLA observations have enabled us to image the neutral hydrogen emission from the bar of NGC 4151 in unprecedented detail, and is a continuation of the work by Pedlar et al. (1992).

Figure 1 shows images of integrated neutral hydrogen emission. The large scale emission extends over approximately 20 kpc and the outer part consists of a well-defined two-armed spiral which originates from a fat bar at a radius of about 5 kpc. The bar shows complex structure, including two sharp features which are reminiscent of the shocks seen in many simulations, e.g., Athanassoula (1992). These features appear to join the central 1-kpc ring discovered by Vila-Vilaró et al. (1994), and for which there appears a partial counterpart in neutral hydrogen emission.
The Role of Chaos in Barred Galaxies
Authors: Contopoulos G. , Voglis N.
Published: July 2016

Ordered orbits in barred galaxies appear along the bar and between the −4/1 and −2/1 resonances of the outer spiral. Chaotic orbits appear mainly near corotation. Such orbits support the bar and the spiral for long times and they are important for self-consistency. There are three main mechanisms for transition from order to chaos: (a) infinite bifurcations, (b) infinite gaps, and (c) infinite spirals. The Lyapunov characteristic number is zero for ordered orbits and positive for chaotic orbits. But much more information is provided by the distribution of the stretching numbers (one-period Lyapunov characteristic numbers). The spectrum of stretching numbers is invariant with respect to initial conditions in a connected chaotic domain. We provide examples of such spectra for 2-D maps, plane galactic orbits, 2-D dissipative systems, 3-D systems (represented by 4-D maps), and systems depending periodically on the time.
General Discussion
Authors: Pfenniger Daniel
Published: July 2016

This contribution presents a general discussion of special topics on barred galaxies by participants in the meeting.
A Multiwavelength Study of the Barred Spiral Galaxy NGC 7479
Authors: Laine S. , Gottesman S. T.
Published: July 2016

The detailed investigation of the activity and dynamics in NGC 7479 confirms the importance of understanding individual galaxies. We have discovered an S-shaped emission structure in 21 cm continuum. This detection together with strong nuclear 10 μm and Hα emission may imply the existence of a central massive black hole. We also address the origin of the asymmetric spiral structure in NGC 7479. The lack of any visible companion and the unperturbed H I velocity field suggest that the asymmetry has an internal origin.
First Analysis of Results of the OH Survey of the Inner Galaxy: Evidence for a Stellar Bar
Authors: Sevenster M. N.
Published: July 2016

Part of a large survey of the inner galactic Plane (|ℓ| < 45° and |b| < 3° total) in the OH 1612MHz line in search for OH/IR stars is analyzed. We find strong evidence for a central m=2 distortion based on geometrical considerations. The observed deviation from axisymmetry cannot be explained by lopsidedness and agrees with other recent models of the galactic Bar on length, inclination and axis ratio.
Reference Coordinate System Requirements for Geodesy and Ocean Dynamics
Authors: Mather R. S.
Published: July 2016

The requirements for systems of reference in geodesy and ocean dynamics should be framed against the background of the distinct possibility of achieving in the foreseeable future measurements with a resolution of 1 part in 108. The current techniques promising this precision, with one exception, are based on observations to extraterrestrial sources/responders. The principal geodetic goals calling for such precision are, broadly stated, the determination of:

1. Positions of stations in global tracking networks.

2. Crustal motion.

3. Polar motion.

4. The radial component of instantaneous sea surface position from satellite altimetry for the estimation of phenomena related to ocean circulation.

5. Earth model improvement.

These goals cannot be achieved without the definition of adequate models for relating measurements from observing stations on Earth to extraterrestrial objects, possibly in an iterative manner in the first instance.

While the specific choice of a system of geodetic reference is not critical for determinations of position in three dimensions, the maintenance of the continuity of geodetic concepts at the highest level of resolution in terms of four-dimensional considerations narrows the possible alternatives available.

Criteria desirable in such a system of reference for observations of the highest precision made from the surface of a non-rigid Earth undergoing secular crustal motion are the following:

1. These observations should be capable of direct relation to the system of reference in four dimensions.

2. The crustal motion vector at a point should be defined in terms of the variations of the coordinatesof that pointwith time.

3. Near-Earth orbital positions should have unambiguous relationships to the origin of ocean geoid determinations in four dimensions.

4. Coordinates on the adopted system of reference should have relevance over an epoch of practical significance (e.g., one year).

5. The scale for the space as obtained from the observations should not be influenced by factors other than the velocity of light and the adopted definition for the second.

An important corollary is that only one point should be treated as “fixed” at the surface of the nonrigid Earth. Positional variations which have a periodic character, effective over an epoch of observation or less, are best treated as effects to be removed from observations by appropriate modeling. Reported secular changes in mean sea level require that the geoid be defined in relation to mean sea level in four dimensions for any determination of sea surface topography, thereby completing a unified system of reference which, would meet all the requirements of high-precision geodesy and ocean dynamics.
Some Problems Related to the Definition of Reference Systems
Authors: Kovalevsky J.
Published: July 2016

The definition of a reference system stands with respect to the physics of the Universe more or less as axiomatics stand with respect to mathematics.

For many centuries, people produced excellent mathematical results using only a few postulates and several so-called evident statements. However, when the foundations of mathematics were analyzed, it became evident that such statements could also be discussed and, since then, axiomatics has become one of the fundamental branches of this science.
Statistical Analysis of Homogeneous Systems of Polar Coordinates
Authors: Proverbio E. , Uras S.
Published: July 2016

In 1972, Proverbio and Quesada compiled a list of seven homogeneous systems of polar coordinates expressed in tenths of years adopted by different authors. In the paper, the authors try to determine the internal correlation of the different systems of coordinates so as to represent the precision of each series for different frequency ranges. The analysis of the standard deviation of the raw residuals of the differences between the coordinates of each series and the mean values from the smoothed curve of the residuals provided further information about the accuracy of the same series of polar coordinates.
1.1.7. Polarization of the Zodiacal Light: First Results from Skylab
Authors: Sparrow J. G. , Weinberg J. L. , Hahn R. C.
Published: July 2016

A brief description is given of the Skylab ten color photoelectric photometer and the programs of measurements made during Skylab missions SL-2 and SL-3. Results obtained on the polarized brightness of zodiacal light at five points on the antisolar hemisphere are discussed and compared with other published data for the north celestial pole, south ecliptic pole, at elongation 90 degrees on the ecliptic, and at two places near the north galactic pole.
2.1.1 In-Situ Records of Interplanetary Dust Particles - Methods and Results
Authors: Fechtig H.
Published: July 2016

A review is given on the techniques used to record and to quantitatively measure data of individual interplanetary dust particles. New developments in detection techniques are briefly discussed.

The main results from recent space missions at about 1 AU and in the earth-moon neighborhood are discussed and compared with the flux results from lunar microcrater studies. Spatial anisotropies and time fluctuations are found indicating that the earth is exposed to two main micrometeoroid dust populations: the “apex”-population and the B-meteoroids. The near planet-dust enrichments measured by HEOS 2 near the earth and by the Pioneer 10/11 near Jupiter are emphasized. The experimental data strongly suggest a fragmentation process associated with the earth. The role of the moon as a dust source is discussed. The important problems in the dust field for future space missions are summarized.
2.1.2 Preliminary Results of the Micrometeoroid Experiment on Board Helios A
Authors: Grün E. , Kissel J. , Fechtig H. , Gammelin P. , Hoffmann H.-J.
Published: July 2016

For the first time in situ measurements of interplanetary dust have been performed between 0.3 AU and 1 AU from the sun by the micrometeoroid experiment on board Helios A. The measured particle masses are between 10−15 g and 10−8 g and their measured speeds are between 2 km/sec and 20 km/sec. Particle impacts are identified by the time-of-flight spectra of the ions released upon impact. 15 large particles (m ≥ 10−12 g) were detected from Dec. 15, 1974 to Sept. 5, 1975. They show a strong increase of the impact rate (appr. a factor of 10) between 1 AU and 0.3 AU. The directions from which they impacted the sensor are concentrated between the solar direction and the apex direction of the Helios spacecraft.
2.2.1 Lunar Microcraters and Interplanetary Dust Fluxes
Authors: Hartung Jack B.
Published: July 2016

Conflicting data for depth-to-diameter ratios for lunar microcrater pits do not permit firm conclusions for distribution of meteoroid densities. The majority of meteoroids have equidimensional shapes. Meteoritic metal spherules have been detected in a small fraction of impact pit glasses, but contribution of meteoroidal material to most pit glasses is small to negligible. Impact pits less than 0.1 microns in diameter (impacting particle mass ~ 10−16 grams) have been observed. Size distributions -9 for microcrater pits less than 50 microns in diameter (particle mass < 10−9 grams) measured on different, samples differ significantly. An inflection in the cumulative size distribution curve at a diameter between 1 and 10 microns (particle masses between 10−14 and 10−11 grams) appears real, supporting the idea of a two-component model for the interplanetary dust. Data for the arrival direction of meteoroids at the moon are inconclusive.
2.2.8 Impact light flash studies: Temperature, Ejecta, Vaporization
Authors: Eichhorn G.
Published: July 2016

Impact experiments have been performed with the 2 MV dust accelerator; the dependence of the maximum light flash energy and intensity on the projectile mass and velocity has been determined experimentally. The temperature of the radiating gas and plasma was estimated to be in the range from 2500K to 5000K, depending on the impact velocity. The distribution of the maximum ejecta speed as well as the normalized distribution of ejected mass have been determined as a function of the ejection angle. A rough estimate of the degree of vaporization of the displaced mass was obtained.
3.4 Optical Properties of Cometary Dust
Authors: Hayakawa S. , Matsumoto T. , Ono T.
Published: July 2016

Optical features of comets suggest that the dust in the coma is composed of a micron size core and a mantle formed by an aggregate of submicron grains.
3.8 Study of the Anti-Tail of Comet Kohoutek from an Observation on 17 January 1974
Authors: Lamy Ph. , Koutchmy S.
Published: July 2016

As Part of our Program of observation of comet Kohoutek at Pic-du-Midi Observatory, we obtained, on January 17.8 UT, 1974 a Photograph in polarized light showing dramatically the (dust) anti-tail extending for almost 1° from the Comet’s head (reported in sky and telescope, June 1974); indeed the comet is visible in polarized light further away than in total light as noticed by weinberg and Beeson (IAU collloquim No. 25, 1974) for Comet Ikeya-Seki. A photometric and polorimetric study was performed (Bücher, A., Robley, R., and Koutchmy, S., 1975, Astron. Astrophys. 39, 289) showing that the anti-tail is strongly polarized (up to 50%). These large degrees of polarisation are of the same order of magnitude as those reported for the tail of comet Ikeya-Seki by matjagin sabitov and kharitonov (1967, Astron. Zh. 44, 1075) and by Weinberg and Beeson (op. cit.). As discussed by these latter authors, particle alignment is precluded as a significant contributor to polarization in the tail of comets. Polarization by large spheres as obtained from the Fresnal reflection coefficients applies only in the case of perfect surface, a circumstance very unlikelyn in the interplanetary space; the scattering is infact controlled by the surface microstructures (Van de Hulst, private communication). Therefore we hypothesized that submicronic grains should play an important role in the anti-tail. The classical method of Finson and Probstein (1968, Astrophys. J. 154, 327, 33) was used to draw the sky plane view of the syndneys for the day of observation. Since the ratio ß of the radiation pressure force to the gravitational attraction is propotional to the third power of the grains’ radius s for s ≲ 0.1 µ, submicronic grains with typical radii of 0.02 µ may indeed be present in the anti-tail and provide a straight-forward explanation observed polarization. This size is of the same order of magnitude as that inferred for interstellar grains which may well be embedded in the comet’s nucleus as well as meteorites for which there exists good evidence. Our conclusion does not rule out the presence of millimeter-size grains as proposed by Sekanina and Gary and O’Dell in their preliminary investigations (1974, Icarus 23, 502, 519) which did not take into account the polarimetric result; such grains may well coexist with the submicronic ones. Finally, the line of maximum intensity is close to a synchrone corresponding to a time of emission 100 days before perihelion passage. This supports the synchronic formation of anomalous tails and possibly of tails as proposed by Vsekhsvyatsky (1932, Astron. Zh. 9, 166).
4.9 On the Structure of Hyperbolic Interplanetary Dust Streams
Authors: Kresák L. , Pittich E.M.
Published: July 2016

The only type of concentration of cometary dust with a reasonable probability of being detected by deep-space probes, are the dust tails emanating from passing comets. Essentially all the dust released from long-period comets leaves the solar system on hyperbolic orbits, because the radiation pressure limit is high (corresponding to centimetre-sized grains emitted in the vicinity of the Earth’s orbit by comets of the Oort’s Cloud). For the short-period comets the dynamical conditions for retention of emitted particles within the solar system are much more favourable, but those which remain in circumsolar orbits tend to disperse rather rapidly (Kresák, 1976a).
Trapezia and Infrared Sources
Authors: Poveda A. , Allen C. , Warman J.
Published: July 2016

From dynamical considerations, a significant fraction of multiple systems of trapezium type is expected to be quite young. A search for positional coincidences between trapezia from various catalogues and infrared sources at 2.2 microns was undertaken. It was found that between 12% and 20% of the trapezia can be associated with infrared sources. Various statistical tests indicate that these coincidences are not likely to be accidental. The nature of the infrared sources associated with trapezia is briefly discussed.
The Statistical Effect of Encounters on Wide Binaries
Authors: King Ivan R.
Published: July 2016

Previous treatments by Ambartsumian and by Cruz-González are combined into a Fokker-Planck equation that describes the time evolution of the distribution of orbit sizes of a set of wide binaries, as encounters with field stars statistically change the orbits. A solution can be found that predicts the distribution of separations greater than about 3000 AU.
The Origin of Multiple Stars by Condensation in Dense Nebulae
Authors: Poveda Arcadio
Published: July 2016

The classical theories of double star formation are briefly reviewed in relation to the origin of multiple stars. Modern observations in the infrared are discussed and their relevance as clues to the process of multiple star formation is stressed. These observations, together with dynamical considerations and data on the statistics of trapezia and hierarchical multiple systems, support the view that multiple stars, in general, are born as trapezia, that is, as independent condensations.
Principles of A Coded Numbering System and Its Application to Open Clusters
Authors: Mermilliod J.C.
Published: July 2016

When we began to collect systematically photometric data it was felt that we needed an appropriate system of identification for our catalogues on magnetic tape. The current system of identification which uses catalogue or list name and star number is best suitable for printed catalogues but brings out many drawbacks when using and intersecting catalogues on magnetic tapes. Thus we developed a coded system of identification with the two basic conditions that it allows to include in the files stars with all possible Kinds of numbering found in the literature, and that computer use was as simple as possible (Mermilliod, 1973).
Systematic Differences in Trigonometric Parallaxes from different Observatories
Authors: Altena W.F.van , Hoffleit E.D. , Smith H.A.
Published: July 2016

Systematic differences in trigonometric parallaxes between Allegheny Observatory and Yale Observatory, between Allegheny Observatory and McCormick Observatory and between the Cape Observatory and Yale Observatory have been investigated for stars common to each pair. The differences found correlate with right ascension, naturally suggesting some sort of annual influence. It is proposed that these differences are related to differences in the annual temperature cycle between observatories, possibly through the mechanism of temperature dependent decentering of the telescope objectives. A dependence upon spectral type was also discovered in the differences between the relative parallaxes from Allegheny and from Yale. Further work is needed to clarify the nature of these systematic effects and to insure that they do not significantly bias available trigonometric parallaxes.

It is proposed that a new parallax catalogue be constructed at Yale after a thorough statistical analysis of all available trigonometric parallaxes has been made. We solicit suggestions and recommendations from interested users.
Random Remarks on Solar Hydrodynamics
Authors: Gough D.O.
Published: July 2016

This is not a review of the literature on solar hydrodynamics, but a discussion of just a few of the Interesting aspects of the subject. It is neither comprehensive, coherent nor well balanced. It concentrates on some of the questions that have been raised recently by new observations and have not yet received much attention, and particularly on topics that were raised at the recent General Assembly of the IAU. Subjects that have been reviewed in the past, such as the propagation of waves in the solar atmosphere and the structure of the solar wind, are avoided. Magneto-hydrodynamics is hardly mentioned at all.
The Interpretation of Line Profiles
Authors: Rybicki G.B.
Published: July 2016

Observations of the shapes and intensities of spectral lines provide a bounty of information about the outer layers of the sun. In order to utilize this information, however, one is faced with a seemingly monumental task. The sun’s chromosphere and corona are extremely complex, and the underlying physical phenomena are far from being understood. Velocity fields, magnetic fields, Inhomogeneous structure, hydromagnetic phenomena – these are some of the complications that must be faced. Other uncertainties involve the atomic physics upon which all of the deductions depend.
Salyut-4 Observations of Active Regions on the Sun
Authors: Bruns A.V. , Grechko G.M. , Gubarev A.A. , Klimuk P.I. , Sevastyanov V.I. , Severny A.B. , Steshenko N.V.
Published: July 2016

We believe that the examination of the ultraviolet solar spectrum is the most informative tool for the diagnostic of the physical state of the solar plasma. But the well known phenomenon of fine structure of active regions (A.R.), as well as of quiet ones, making spectral lines to be wavy and patchy (across dispersion) demands

a) high spatial resolution on the solar image and b) stigmatic spectra.
Absence of velocity anisotropy in the direction of the Virgo cluster
Authors: Kormendy John
Published: July 2016

Nous présentons une méthode de mesure des distances des galaxies elliptiques basée sur une relation entre la brillance superficielle et un rayon déduit de la distribution spatiale de l’intensité de lumière émise. Nous confrontons ensuite les distances calculées à partir de la vitesse pour 11 galaxies de l’amas de la Vierge, avec celles de 8 objets de plus grand décalage spectral pour la plupart. Ceci implique que l’amas de la Vierge est à une distance plus faible que celle donnée par sa vitesse: , résultat négatif confirmant la conclusion de Sandage et Tammann (1974, 1975), à savoir la non existence d’une vitesse particulière de l’amas de la Vierge.
The Hubble diagram for Seyfert galaxies and related objects
Authors: Khachikian Edward Ye. , Weedman Daniel W.
Published: July 2016

Nous présentons les diagrammes magnitude-décalage spectral et diamètre angulaire-décalage spectral pour les galaxies de Sey-fert. Tous deux montrent des corrélations indiquant que les décalages vers le rouge sont cosmologiques. Les luminosités des noyaux des Seyfert de classe I sont comparées â celles des QSO en utilisant des nouvelles mesures de flux de raies en émission. La continuité des luminosités, bien établie, avec des galaxies de Seyfert couvrant un intervalle de luminosité plus grand que les QSO est une indication que les décalages vers le rouge des QSO sont aussi de nature cosmologique.
Possible explanations of non cosmological redshift
Authors: Pecker Jean-Claude
Published: July 2016

Après une introduction résumant l’essentiel des faits d’observation à interpréter, la section I étudie successivement différentes suggestions: perturbations de cosmologies relativistes, chronogéométrie de Ségal, cosmologie à explosions successives d’Ambartsumian, variation des constantes physiques, enfin mécanismes de fatigue de la lumière. Une forme particulière de ces derniers mécanismes est discutéedans la section II, où il est montré qu’on peut, grâce à une interaction, décrite en détails, entre les photons de la source et les particules φ (particules scalaires, neutres, de très faible masse et de spin zéro), expliquer les décalages anormaux vers le rouge, mais aussi peut-être (section III) la loi normale de Hubble et le rayonnement à 3 K. Une conclusion montre à quel point le débat reste ouvert.
Conclusion
Authors: Morrison Philip
Published: July 2016

La conférence est résumée par un Copernicien radical: nous pouvons mieux comprendre le monde lointain à partir de la compréhension que nous avons ici. Trois vastes questions sont incluses: le programme de Hubble, étude du flux cinématique des galaxies, principalement à bas décalages vers le rouge, afin d’évaluer les constantes à z > ¼, avec une attention spéciale aux déviations à la simplicité, et au rayonnement de corps noir; la physique des décalages spectraux en général.
Low Surface Brightness Dwarf Galaxies in Nearby Clusters
Authors: Chiboucas Kristin , Mateo Mario
Published: July 2016

We present initial results of a study of low surface brightness dwarf galaxies within galaxy clusters at z ≤ .03 as part of our program to determine the clustering properties, luminosity functions, and morphologies of dwarf galaxies in a wider range of cluster environments. In addition to deep V-band images covering up to 1 deg2 in each of 13 different clusters, we have obtained velocities from fiber spectroscopy for 235 galaxies in A3526. In A3526, we find a drop in cluster galaxy counts at intermediate magnitudes which is supported by our spectroscopic results.
Low Surface Brightness Galaxies Beyond Z = 0.5: Existence, Detection and Properties
Authors: Bothun G.
Published: July 2016

I argue that low surface brightness disks evolve sufficiently slowly that, at any redshift, there should be a high space density of these objects. Cosmological dimming, in combination with the tenacity of Freeman’s Law, will make their direct detection very difficult. Given their abundance at z =0, it seems reasonable to suggest that such hidden galaxies will be important absorbers along the line of sight to distant QSOs.
HI Properties of LSB Dwarf and Blue Compact Dwarf Galaxies
Authors: Taylor C.L. , Brinks E. , Skillman E.D.
Published: July 2016

We present high resolution (~ 15″) VLA HI observations of one LSB dwarf galaxy and 5 Blue Compact Dwarfs. Previous works have emphasized the difference in the peak column density of the HI between the two types of galaxy. However, the peak column density is typically only a factor of 2—4 greater in BCDs than in LSB dwarfs, suggesting that the difference between the two is one of degree, not quality. The HI morphologies of the two types are often quite similar.
Cosmic Baryon Density from Primordial Nucleosynthesis and Other Evidence
Authors: Pagel B.E.J.
Published: July 2016

I comment on primordial abundances, their implications for cosmic baryon density (all are consistent with 4 ≤ η10 ≤ 5), the nature of baryonic dark matter (probably mainly hot intergalactic gas), its metallicity and implications for the overall yield. Recent estimates of the cosmic star formation rate as a function of red-shift are discussed in the light of the present-day densities of stars and heavy elements.
Helium Abundance in the Most Metal-Deficient Dwarf Galaxies
Authors: Izotov Y.I.
Published: July 2016

The high-quality long-exposure spectroscopic observations of the two most-metal deficient blue compact galaxies I Zw 18 and SBS 0335–052 are discussed. We confirm previous findings that underlying stellar absorption strongly influences the observed intensities of He I emission lines in the brightest NW component of I Zw 18, and hence this component should not be used for primordial He abundance determination. The effect of underlying stellar absorption, though present, is much smaller in the SE component. The extremely high signal-to-noise ratio spectrum (≥ 100 in the continuum) of the BCG SBS 0335–052 allows us to measure the helium mass fraction with precision better than 2% in nine different regions along the slit. The weighted mean of helium mass fraction in two most metal-deficient BCGs I Zw 18 and SBS 0335–052, Y=0.2462±0.0009, after correction for the He production in massive stars results in primordial He mass fraction Yp = 0.2452±0.0009.