bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reference Coordinate System Requirements for Geodesy and Ocean Dynamics
Authors: Mather R. S. 
Published: July 2016

AbstractThe 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

AbstractIn 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

AbstractA 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

AbstractA 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

AbstractFor 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

AbstractConflicting 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

AbstractImpact 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.
3.8 Study of the Anti-Tail of Comet Kohoutek from an Observation on 17 January 1974
Authors: Lamy Ph. , Koutchmy S. 
Published: July 2016

AbstractAs 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).
Trapezia and Infrared Sources
Authors: Poveda A. , Allen C. , Warman J. 
Published: July 2016

AbstractFrom 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

AbstractPrevious 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

AbstractThe 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.
Systematic Differences in Trigonometric Parallaxes from different Observatories
Authors: Altena W.F.van , Hoffleit E.D. , Smith H.A. 
Published: July 2016

AbstractSystematic 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.
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) demandsa) high spatial resolution on the solar image and b) stigmatic spectra.
Possible explanations of non cosmological redshift
Authors: Pecker Jean-Claude 
Published: July 2016

RésuméAprès 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.
Low Surface Brightness Dwarf Galaxies in Nearby Clusters
Authors: Chiboucas Kristin , Mateo Mario 
Published: July 2016

AbstractWe 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

AbstractI 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

AbstractWe 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

AbstractI 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

AbstractThe 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.
The fate of dwarf satellite galaxies (or: Can we observe soft merging?)
Authors: Richter G. , Vennik J. , Böhm P. , Capaccioli M. 
Published: July 2016

AbstractDwarf satellite galaxies and globular clusters bound to luminous (in particular early type) galaxies, can be steered by interactions to orbits penetrating deep into the potential of their parent galaxy, where the outer stars are eroded and the dwarf satellite is completely destroyed in a relatively short time, resulting in very faint disturbances (soft merging) in the form of faint rings in the parent galaxy.With special image processing methods we have found faint structures in E and SO galaxies, which for many reasons (mass, statistics, etc.) can be interpreted as observational evidence of this type of soft merging. This debris of dwarf satellites can provide a considerable part of the mass of the parent galaxy.
Neutral Hydrogen in HCG 95
Authors: Huchtmeier W. K. , Verdes-Montenegro Lourdes , Yun Min , del Olmo A. , Perea J. 
Published: July 2016

AbstractWe have observed Hɪ emission and radio continuum emission from the compact group of galaxies HCG 95 with the Very Large Array (VLA)1. Two continuum sources coincide in with galaxies in this group: HCG 95 B (3.9 mJy) and HCG95C (6 mJy). Hɪ emission and absorption was detected in galaxy HCG 95 C. In addition we detected two so far unknown dwarf galaxies by their Hɪ emission within 3.5 arcmin of the group center. We did not detect galaxy b (with ç = 8000 kms−1 it is obviously a foreground object) and galaxy d — an edge-on Sc galaxy. This group definitely is Hɪ deficient compared with the average Hɪ content expected for spiral galaxies of the same luminosity and type. The first-ranked elliptical galaxy HCG 95 A might be responsible for the observed Hɪ deficiency in this group.
X-ray Observations of Poor Groups
Authors: Mulchaey John S. 
Published: July 2016

AbstractX-ray observations of groups have provided considerable new insight into these cosmologically important systems. Recent ROSAT surveys of loose and compact groups suggest that ≃ 50% of all nearby groups contain a hot intragroup medium, including many spiral-rich groups. However, spiral-only groups tend not to be X-ray detected. Spectroscopic studies of X-ray groups indicate that these systems contain a large number of faint galaxies. The existence of a large population of faint galaxies, combined with the extended X-ray halos, is consistent with X-ray detected groups being real, bound systems. The nature of non-X-ray detected groups, which do not contain an extensive faint galaxy population, is still unclear.ROSAT observations have also revealed the existence of individual elliptical galaxies with X-ray properties and total masses similar to those of X-ray groups. These objects may be the merger remnants of X-ray groups or ‘failed groups’ (i.e. overdensities that formed only a single galaxy). The number density of these objects suggests they make a non-negligible contribution to the mass density of the universe.
Regular and Chaotic Motion in a Restricted Three–Body Problem of Astrophysical Interest
Authors: Muzzio J. C. , Wachlin F. C. , Carpintero D. D. 
Published: July 2016

AbstractWe have studied the motion of massless particles (stars) bound to a stellar system (a galactic satellite) that moves on a circular orbit in an external field (a galaxy). A large percentage of the stellar orbits turned out to be chaotic, contrary to what happens in the usual restricted three–body problem of celestial mechanics where most of the orbits are regular. The discrepancy is probably due to three facts: 1) Our study is not limited to orbits on the main planes of symmetry, but considers three–dimensional motion; 2) The force exerted by the satellite goes to zero (rather than to infinity) at the center of the satellite; 3) The potential of the satellite is triaxial, rather than spherical.
Triplets of Galaxies: Some Dynamical Aspects
Authors: Aceves Héctor 
Published: July 2016

In celestial mechanics the 3-body problem has a long and rich history, yet the particular problem of 3-galaxy systems has been rather less studied (see review by Valtonen & Mikkola 1991). Most of the up-to-date works have addressed the 3-galaxy problem using a point-like approach, although some explicit-physics simulations have been performed to simulate dynamical friction effects and merging processes (Zheng et al. 1993). These studies have provided important understanding on the general behaviour of observed galaxy triplets (Karachentsev 2000), and some accordance with observations has been obtained.However galaxies are not point-like particles, but rather consist of a large number of stars which can be approximated as point-like particles. Qualitative and quantitative differences result in the dynamics when the 3-galaxy problem is addressed self-consistently; i. e. when galaxies are able to redistribute energy and angular momentum among their stars. Since not using self-consistent galaxies necessarily casts some doubts on earlier results, we address here the 3-galaxy problem self-consistently and compare some results with observations. A full report on this work is in preparation.