bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Initial Eigenorbits for Asteroids
Authors: Muinonen Karri , Milani Andrea , Bowell Edward
Published: July 2016

We consider initial determination of asteroid orbits in the case of small numbers of observations and short observational arcs. For asteroids having long arcs, we can assess the orbital uncertainties with the help of the covariance matrix that, in the phase space of the orbital elements, defines a set of probability ellipsoids. In initial orbit determination, because of the nonlinear characteristics and multiple solutions of the inversion problem, we cannot readily use the covariance matrix to estimate the orbital uncertainties. However, by computing the eigenvalues and eigenvectors of the formal correlation matrix (that is, by deriving the eigenorbits), we can discern the most indeterminate orbital elements. Here we solve the eigenproblem for 17 single-apparition asteroids.
Gravitational Capture to Resonance Rotation of the Early Moon in General Relativity and Gravitation
Authors: Gusev Alexander
Published: July 2016

The capture of the Moon represents a very unique event in the history of the solar system (Singer, 1968; Goldreich et al., 1975; Goldreich, 1966). The Moon formed separately in a heliocentrical orbit similar to the Earth’s and was later captured by the Earth. The capture of the Moon defines also a severe heating event where the Earth’s kinetic energy of rotation is largely dissipated by the mechanism of tidal friction.

A corrected tidal theory (Singer, 1977) leads to a dramatically different result of MacDonald’s theory (MacDonald, 1964) suggesting lunar capture from a prograde orbit.
Analysis of LLR Data by the Program System ERA
Authors: Aleshkina E.Yu. , Krasinsky G.A. , Vasilyev M.V.
Published: July 2016

Some results of analysis of lunar ranging data of 1969–1995 are presented. A relevant dynamic theory has been constructed by numerical integration of the equations of motion of the major planets and the Moon and of lunar libration equations. To make the dynamical theory completely self-consistent an optional approach is tested in which the equations of Earth rotation are integrated simultaneously. Partial derivatives with respect to estimated parameters are also obtained by numerical integrations of variational equations. Preliminary results of evaluation of a large set of parameters involved in the lunar ranging data are presented.
New Approach to the Earth’s Rotation Problem Consistent with the General Planetary Theory
Authors: Brumberg V.A. , Ivanova T. V.
Published: July 2016

The equations of the translatory motion of the major planets and the Moon and the Poisson equations of the Earth’s rotation in Euler parameters are reduced to the secular system describing the evolution of the planetary and lunar orbits (independent of the Earth’s rotation) and the evolution of the Earth’s rotation (depending on the planetary and lunar evolution).
Geosynchronous Satellite Orbit Determination
Authors: Rudenko Sergei
Published: July 2016

The paper presents the results of the orbit determination of geosynchronous satellites derived from 1921 positional observations of a few dozens of satellites obtained at the double wide-angle astrograph DWA (D=0.4m, F=2m) of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine in 1985–1991. The observations cover the longitude range from 19°Wto 80°E. Orbital inclination of the observed objects is less than 3°. The mean values of the rms residuals are 066 in R.A. and 101 in Dec. over all processed orbital arcs.
Ideal Frame and Multi-Revolution Methods for Space Debris Dynamics
Authors: Calvo C. , Melendo B. , Palacios M.
Published: July 2016

Using the computational advantages offered by the formulation of orbital problems with respect to the ideal frame, with or without regularization, we consider the multi–revolution methods to obtain numerically the short and long–term propagation of the resulting debris clouds after a breakup event of an operational satellite. The problem posed and solved in this form gives high efficiency. We think that software with these features will serve two purposes: it will support studies of the hazards of space debris for operational orbital space systems and also will help to create debris analysis programs more transferable and reliable.
Semi-Analytical and Semi-Numerical Methods in Celestial Mechanics
Authors: Breiter Slawomir
Published: July 2016

Many quite different theories and methods of celestial mechanics are referred to as semi-analytical or semi-numerical. Their common feature is the trade-off of a generality for a computational efficiency. Four main ideas behind semi-analytical theories are identified and reviewed: series contraction, analytical support of numerical integration, piecewise solutions, and numerical evaluation of action-angle variables. The role of numerical analysis tools in analytical theories is briefly discussed.
Optical-Radio Reference Ties
Authors: Kovalevsky J.
Published: July 2016

In the course of the Hipparcos data reduction, the system of coordinates obtained is the result of complicated and partly random processes. It is therefore an arbitrary system which could not be retained. It was decided to compute a rotation ϵ at epoch (1991.25) and a time-dependent rotation ω (or spin) such that, when applied, it would be a realisation of the IAU extragalactic reference system as defined in 1991 and implemented by IERS in 1995.

A working group was set up by the Hipparcos Science Team with the task to provide these rotations from all possible techniques. Actually eleven independent teams provided a solution. One can group them in four categories.

1.

Radio techniques included VLBI observations with the US Deep Space Network, VLBA and the European VLBI Network, and connected radio interferometers MERLIN and VLA. While VLBI provided a solution for both ϵ and ω, the other techniques allowed to get only ϵ.

2.

Medium and small field astrometry including the optical positions of compact sources (Hamburg and USNO), and observations with the HST which both provided solutions for ϵ only and comparisons of plates taken at large intervals of time (Bonn and Potsdam) which gave solutions for ω only.

3.

Star catalogues refered to galaxies: Lick Northern proper motion program, Yale Southern proper motion program, and KSZ catalogue. Yale University, ARI in Heidelberg and Kiev Observatory yielded solutions for ω.

4.

Comparison of Earth rotation parameters as obtained by VLBI and by a reduction of ground-based determinations with Hipparcos data (Prague Observatory) gave components of ϵ and ω in the equator.
Determination of Nutation and Precession Based on Observations with the Pulkovo Polar Tube
Authors: Kotreleva Olga V. , Naumov Vitalj A.
Published: July 2016

Since 1953 regular observations have been carried out with the polar photographic tube (PT) of A. A. Mikhailov at Pulkovo, a fixed astrograph (D = 200 cm, F = 600 cm) which can take photographs of a circumpolar zone of 60′radius. An analysis of measured polar distances of the same 30 stars on each plate gives corrections to the adopted values of coefficients of the nutation and precession constant. Though several papers have appeared during the last decade in which VLBI and LLR observations were used for the determination of the nutation coefficients and precession constant, the results from a 40-year series of observations with the PT are of interest, because of its two-times period of the principal nutation term. The method is fully independent.
Astrometric Positions of Quasars by CCD Observations
Authors: Assafin M. , Vieira Martins R. , Andrei A.H.
Published: July 2016

We present results of CCD observations for 85 quasars with −80° ≤ δ ≤ +20° declination, belonging to the International Celestial Reference System (ICRS). The positions are referred to the Carlsberg Series (CAMC) and PPM catalogues. We discuss a method which allows one to obtain precise positions based only on CCD observations, on the use of the Digitized Sky Survey of ST ScI and on the Guide Star Catalogue. The results are compared with the VLBI positions.
Observations of the Association of Prominences and the Surrounding Corona
Authors: Smartt Raymond N. , Zhang Zhenda , Airapetian Vladimir S. , Kim Ira S.
Published: July 2016

Emission-line coronal images in Fe XIV (530.3 nm) and FeX (637.5 nm) show faint enhancements at the location of quiescent prominences. Such enhancements can appear in the outer portions of a prominence, similar to the high-temperature sheath surrounding prominences as inferred from UV and EUV observations. The observational evidence supports the interpretation that this enhanced coronal emission is due to energy carried by the prominence threads and dissipated in the adjacent coronal region. Also, observed coronal loop interactions involving partial magnetic reconnection have associated Hα structures. These structures can have the appearance of an active prominence, similar to those typically observed in post flare loop systems. It appears that the association of such active prominences with the adjacent corona is fundamentally different from that of quiescent prominences. The observations indicate that these types of active prominences arise simply as a consequence of reconnection processes in the corona itself.
Are Prominences Formed by Flux Convergence?
Authors: Galsgaard K. , Longbottom A.W.
Published: July 2016

Numerical 3D resistive MHD experiments are used to investigate the dynamical properties of a quadrupolar magnetic field, as the two dipolar regions are pushed together. A current concentration is formed between the approaching flux concentrations and, when reconnection starts, material is lifted against gravity. As it rises the material spreads out along the polarity inversion line and forms a prominence-like structure.
Causes and Effects of Filament Eruptions
Authors: Filippov Boris P.
Published: July 2016

Observational and theoretical aspects of filament destabilization are reviewed in light of the concept of filament eruption as catastrophic loss of equilibrium in a magnetic configuration of inverse polarity. Interrelations between eruptive prominences and other phenomena of solar activity such as flares, CMEs, and loop arcade are considered.
Solar and Stellar Dynamo Waves Under Asymptotic Investigation
Authors: Kuzanyan Kirill M.
Published: July 2016

The main magnetic activity of the Sun can be visualised by Maunder butterfly diagrams which represent the spatio-temporal distribution of sunspots. Besides sunspots there are other tracers of magnetic activity, like filaments and active regions, which are observable over a wider latitudinal range of the Sun. Both these phenomena allow one to consider a complete picture of solar magnetic activity, which should be explained in the framework of one relatively simple model.

A kinematic αѡ-dynamo model of the magnetic field’s generation in a thin convection shell with nonuniform helicity for large dynamo numbers is considered in the framework of Parker’s migratory dynamo. The obtained asymptotic solution of equations governing the magnetic field has a form of a modulated travelling dynamo wave. This wave propagates over the most latitudes of the solar hemisphere equatorwards, and the amplitude of the magnetic field first increases and then decreases with the propagation. Over the subpolar latitudes the dynamo wave reverses, there the dynamo wave propagates polewards and decays with latitude. Butterfly diagrams are plotted and analyzed.

There is an attractive opportunity to develop a more quantitatively precise model taking into account helioseismological data on differential rotation and fitting the solar observational data on the magnetic field and turbulence, analyzing the helicity and the phase shift between toroidal and poloidal components of the field.
Large-Scale Patterns of Prominences in the Global Solar Cycles During 1880–1995
Authors: Callebaut Dirk K. , Makarov Valentine I. , Tavastsherna Ksenia S.
Published: July 2016

The zonal distribution of prominences, their poleward migration from the sunspot zone to the poles, the polar magnetic field reversals and a correlation of the mean latitude of filament bands at minimum activity with the maximum of Wolf number in the next cycle are briefly discussed for the period 1880–1995. The need for research on the longterm latitude distribution of the prominences is emphasized. New results concerning long-term variations of the torsional oscillations of the Sun and quasi-periodic oscillations of the latitude zonal boundaries from an analysis of Hα charts (1915–1990) are given.
Reconstruction of Sun-as-Star Magnetic Field Structure and Evolution Using Filament Observations
Authors: Ponyavin Dmitri I.
Published: July 2016

A technique is used to restore the magnetic field of the Sun viewed as star from the filament distribution seen on Hα photographs. For this purpose synoptic charts of the large-scale magnetic field reconstructed by the McIntosh method have been compared with the Sun-asstar solar magnetic field observed at Stanford. We have established a close association between the Sun-as-star magnetic field and the mean magnetic field inferred from synoptic magnetic field maps. A filtering technique was applied to find correlations between the Sun-as-star and large-scale magnetic field distributions during the course of a solar cycle. The correlations found were then used to restore the Sun-as-star magnetic field and its evolution in the late 1950s and 1960s, when such measurements of the field were not being made. A stackplot display of the inferred data reveals large-scale magnetic field organization and evolution. Patterns of the Sun-as-star magnetic field during solar cycle 19 were obtained. The proposed technique can be useful for studying the solar magnetic field structure and evolution during times with no direct observations.
Spectrographs for the Measurement of Radial Velocities
Authors: Baranne André
Published: July 2016

In this article I discuss the design of échelle spectrographs for the measurement of radial velocities. I consider the attainment of very high precision, and whether we can do still better than the current generation of instruments, and what problems have been resolved and what problems still remain to be solved in spectrograph design. The article makes special reference to the design principles followed in the Marseille-Geneva instrument ELODIE, for which the goal has been the measurement of stellar radial velocities of high precision using an R4 échelle grating.
A new spectrograph dedicated to precise stellar radial velocities
Authors: Bouchy F. , Connes P. , Bertaux J.L.
Published: July 2016

The fiber-fed echelle spectrograph EMILIE designed for the measurement of stellar radial-velocity changes is presently being laboratory-tested. Using a 204 × 408 mm grating and a 1k × 1k CCD detector, it samples about 50% of the 410−620 nm wavelength range with spectral resolution R ∼ 150 000. This spectrograph is coupled to the telescope via a single 50μm fiber, which accepts 2.7 arcsec from the sky. An automatic guiding system stabilizes the image at the entrance of the fiber. The fiber transmits alternately to the spectrograph the stellar beam and the reference beam. The same pixels of the CCD detector are used alternately for the two spectra, which requires an excellent short term stability. Hence, later on, the spectrograph will be located within a vacuum tank, with active thermal control. The instrument will be set up at the focus of the 1.52-m coudé telescope at the Observatoire de Haute-Provence (OHP) and will undertake programs of asteroseismology and detection of extrasolar-planets.
Precision versus Accuracy: some astrophysical and operational limitations
Authors: Griffin R. E. M.
Published: July 2016

The measurement of accurate radial velocities for A- or B-type dwarfs poses a separate category of problems: the small number of suitable lines, the wide wavelength range over which such lines are distributed, thermal broadening, rotational broadening, line distortions caused by rotating spots, spectrum variations due to obvious duplicity, and low-level velocity variations due to undetected companion spectra. Moreover, the fact that A- and B-type spectra fall into very distinct groups, each with its own sub-set of the above problems, means that it may be both difficult and unsatisfactory to specify velocity standards, since intrinsic uncertainties caused by differences in spectral type may exceed the measuring errors. The investigation summarized here into the nature and magnitude of some of these intrinsic errors employs wide spans of high-resolution, high-dispersion spectra of Sirius and Vega as ‘natural’ templates. Attention is also drawn to systematic errors which may arise (a) when modelling a cross-correlation ‘dip’ and (b) whenever a spectrum or a cross-correlation dip is measured in the unavoidable presence of another such spectrum or dip.
Exactly What Is Stellar ‘Radial Velocity’?
Authors: Lindegren Lennart , Dravins Dainis , Madsen Søren
Published: July 2016

Accuracy levels of metres per second require the concept of ‘radial velocity’ to be examined, in particular with respect to relativistic velocity effects and spectroscopic measurements made inside gravitational fields. Already in a classical (non-relativistic) framework the line-of-sight velocity component is an ambiguous concept. In the relativistic context, the observed wavelength shifts depend e.g. on the transverse velocity of the star and the gravitational potential at the source. We argue that the observational quantity resulting from high-precision radial-velocity measurements is not a physical velocity but a spectroscopic radial-velocity measure, which only for historic and practical reasons is expressed in velocity units. This radial-velocity measure may be defined as cz, where c is the speed of light and z is the observed relative wavelength shift reduced to the solar system barycentre. To first order, cz equals the line-of-sight velocity, but its precise interpretation is model dependent.
Absolute Radial Velocities by Cross-Correlation with Synthetic Spectra
Authors: Skuljan J. , Hearnshaw J. B. , Cottrell P. L.
Published: July 2016

Precise absolute radial velocities have been measured for several hundred late-type stars at Mt John University Observatory with the 1-m telescope, fiber-fed échelle spectrograph, and Thomson CCD. Six échelle orders in the green (5000−5600 Å) are used. Many delicate steps have been undertaken in order to maintain exactly the same conditions, both in recording and reducing the spectra, over a period of 18 months. A cross-correlation technique with theoretical spectra computed by R. L. Kurucz has been chosen to determine the absolute radial velocities. Blue sky spectra have been used to monitor systematic zero-point fluctuations from one observing run to another. An additional correlation between the measured velocities and average number of A/D units in the continuum has been discovered and used for fine adjustments, significantly improving the results. A random uncertainty of 10–20 ms−1 has been achieved for stellar spectra having intrinsically constant radial velocities.
The Texas High-Precision Radial-velocity Programs
Authors: Cochran William D. , Hatzes Artie P.
Published: July 2016

Several different high-precision radial-velocity programs are now underway at The University of Texas. This paper discusses the aspects of these programs that are related to the problem of detection of extrasolar planetary systems. This includes the McDonald Observatory Planetary Search program on the McDonald 2.7-m Harlan Smith Telescope, an accompanying program of high-resolution stellar line profile measurement, the European Southern Observatory planetary search program, the Keck Hyades survey, and the Hobby∙Eberly Telescope planet surveys. Here, we summarize each of these programs, and present recent results from each.
The Advanced Fiber-optic Echelle (AFOE) and Extrasolar Planet Searches
Authors: Nisenson P. , Contos A. , Korzennik S. , Noyes R. , Brown T.
Published: July 2016

The Advanced Fiber-Optic Echelle (AFOE) is a fiber-fed bench-top spectrograph specifically designed for precise radial velocity observations. The AFOE is permanently located at the 1.5-m telescope at Smithsonian’s Whipple Observatory in Arizona and is regularly used for monitoring exo-planet candidate stars and for asteroseismology observations. In this paper, we discuss the status of the instrument, as well as an upgrade to the instrument, a Fabry-Perot reference, which may prove important both for the AFOE and for all precise radial velocity (PRV) facilities.
Doppler Imaging of Stellar Oscillations: Multi-Site Observations of Epsilon Cephei
Authors: Kennelly E. J. , Brown T. M. , Ehrenfreund P. , Foing B. , Hao J. , Horner S. , Korzennik S. , Nisenson P. , Noyes R. , Sonnentrucker P.
Published: July 2016

We investigate the oscillation properties of є Cep using a series of specialized techniques designed to extract and analyze time variations in absorption line profiles. To obtain the necessary temporal coverage for this investigation, multi-site observations were collected at 3 sites (China, France, Arizona) all equipped with high-resolution échelle spectrographs. From these observations, we find evidence for a very rich spectrum of modes in є Cep.
Convective Lineshifts in the Infrared Region of the Solar Spectrum
Authors: Hamilton Devon , Lester J. B.
Published: July 2016

Convective motions in the photospheres of the Sun and solar-type stars can be studied using spectral line asymmetries via line bisectors and line shifts. Over the past few years there has been an improvement in the precision of the line positions for Fe I, CO and OH. These improved positions can be combined with recent high resolution infrared spectra of the Sun to examine how their convective line asymmetries behave with respect to observable line parameters, such as wavenumber and depth. We have completed a survey of convective line shifts for over 650 Fe I lines, 1320 CO lines and 80 OH lines, between 0.9 and 11 μm. The behavior of the distributions of these features, with respect to observed characteristics, is examined. The use of different species allows for an exploration of convective motions at different levels in the solar atmosphere. The large size of the sample allows for a more complete statistical understanding of the distributions. This work complements surveys of line asymmetries in the visible region of the Solar spectrum, and provides a foundation for further studies of convective motions in the spectra of other stars.
The Status of Early-Type Radial-Velocity Standards
Authors: Fekel Francis C.
Published: July 2016

A search for constant velocity B and A stars for use as early-type radial-velocity standards has continued for 15 years. For the past decade observations of over two dozen stars have been obtained with the KPNO coudé feed telescope, spectrograph, and a CCD detector. Mean velocities are given for 26 B and A stars plus HR 5447, an F2 V star. Unfortunately, most of the early and mid B-type stars have variable velocities. However, a number of slowly rotating, late B and A-type stars that have constant velocities are identified. From 53 velocities covering nearly 20 years, a preliminary orbit for the early-A star HR 8641 = o Peg has been determined. It has a period of 10.8 years and a total velocity amplitude of 2.4 km s−1.
Derivation of orbital parameters of very low mass companions in double stars from radial velocities and observations of space astrometry missions like HIPPARCOS, DIVA and GAIA
Authors: Bernstein H.-H.
Published: July 2016

Radial velocity measurements are a well known high-precision method to obtain the orbits of extrasolar planets or brown dwarfs. However, this method is not able to determine the inclination which could be derived from astrometry. The astrometric effects of those objects are very minute, wherefore the interest of astronomers in astrometric techniques was very poor. This situation changes fundamentally since space astrometry observations are available. HIPPARCOS demonstrated the power of space astrometry and the extremely high accuracy of the DIVA, and especially the GAIA observations allows one to detect Jupiter- and Earth- like objects. The optimal estimation of the parameters of the orbit of extrasolar planets or brown dwarfs is a combination of radial velocity measurements and space astrometry observations. Here it is possible to overcome problems which are inherent in both observation methods, so space astrometry complements radial velocity observations and vice versa. This paper gives a method for the parameter estimation using both types of measurements.
Photographic Fireball Networks
Authors: Halliday Ian
Published: July 2016

Three networks for the photography of bright fireballs are now in operation; in the central United States, central Europe and western Canada. A detailed comparison is made of the parameters which describe the three networks. Although only two meteorites for which photographic orbital data is available have been recovered, the networks are contributing valuable data on fireball orbits, influx rates and problems of meteor physics.
The Auroral Green Line in Perseid Spectra Near Sunspot Maximum
Authors: Russell John A.
Published: July 2016

Thirty-one spectra photographed during the Perseid showers of 1969 and 1970 are found to exhibit greater ionization and stronger, more frequent appearance of the forbidden oxygen line at 5577 Å than Perseid spectra obtained with the same instrument in 1961. Data from 13 Perseid showers indicate a relationship between the frequency of occurrence of the oxygen line and solar activity. In 1969-70, near sunspot maximum, the strength of this so-called auroral green line is greatest near shower maximum, as though the nature of the meteoroids were a function of their distance from the core of the stream, or, alternatively, the strength of the green line were a function of the altitude of the radiant.
Image-Orthicon Spectra of Geminids in 1969
Authors: Millman P. M. , Cook A. F. , Hemenway C. L.
Published: July 2016

The spectra of 25 meteors, recorded with an image-orthicon technique in December 1969, are studied in relation to similar records made in August of the same year. Of 19 Geminid meteors in the absolute visual magnitude range 0 to + 2, only one showed any evidence of the forbidden line of oxygen at 5577 Å, while all Perseid meteors recorded in August exhibited the oxygen line, a result of the large difference in geocentric velocity between the two showers. Atoms identified in faint Geminid meteors include neutral iron, magnesium, calcium and sodium. The molecular bands of nitrogen are also observed.
A Working List of Meteor Streams
Authors: Cook Allan F.
Published: July 2016

This Working List which starts on the next page has been compiled from the following sources:

(1)

A selection by myself (Cook, 1973) from a list by Lindblad (1971a), which he found from a computer search among 2401 orbits of meteors photographed by the Harvard Super-Schmidt cameras in New Mexico (McCrosky and Posen, 1961)

(2)

Five additional radiants found by McCrosky and Posen (1959) by a visual search among the radiants and velocities of the same 2401 meteors

(3)

A further visual search among these radiants and velocities by Cook, Lindblad, Marsden, McCrosky, and Posen (1973)

(4)

A computer search by Lindblad (1971b) among 1827 precisely reduced photographed meteors from all available sources

(5)

Visual radiants reported by Hoffmeister (1948)

(6)

A report on the Phoenicid shower of December 5, 1956, by Ridley (1962)

(7)

A list of visual radiants by Mcintosh (1935)

(8)

A report on the June Lyrids by Hindley (1969)

(9)

Two papers on radar radiants in the southern sky by Weiss (1960a, b)

(10)

A paper on radar radiants in the southern hemisphere by Nilsson (1964)

(11)

Several compilations of visual, photographic, and radar radiants by Whipple and Hawkins (1959), McKinley (1961), Millman and McKinley (1963), and Jaechia (1963)
New Evidence for Interplanetary Boulders?
Authors: Sekanina Zdenek
Published: July 2016

The present paper critically discusses the method of detection, the magnitude and the rate of occurrence of sudden disturbances in the motions of some short-period comets. The disturbances have recently been suggested as potential indicators of collisions between the comets and interplanetary boulders—minor objects whose existence was predicted by M. Harwit in 1967. The character of explosive phenomena, caused by an impact of such a boulder on a comet’s nuclear surface, depends significantly on the surface texture of the target body. To advance our understanding of the impact mechanism, a method is suggested which would supply a good deal of the missing information about the structure and optical properties of nuclear surfaces from precise photometric observations of cometary nuclei at large solar distances.
Optical Properties of Atmospheric Dust From Twilight Observations
Authors: Divari N. B. , Zaginayilo Y. I. , Kovalchuk L. V.
Published: July 2016

Three methods of approximation are described and are used to separate the primary twilight brightness from the observed brightness. Photoelectric observations obtained at the Majaky Observatory in 1968-69 (Zaginayilo) are combined with observations from a balloon and from Pic-du-Midi Observatory (Link et al., 1967) to derive the atmospheric scattering phase functions at 0.37 μ and 0.58 μ as a function of height.

Comparison of these data with data for a Rayleigh atmosphere provide information on the optical properties of dust in the upper atmosphere.
On the Primordial Condensation and Accretion Environment and the Remanent Magnetization of Meteorites
Authors: Brecher Aviva
Published: July 2016

Attention is drawn to the fact that neither astronomical observations, nor laboratory data can, as yet, sufficiently constrain models of the origin and evolution of the solar system. But, if correctly approached and interpreted, the magnetic remanence of meteorites could help in constructing a self-consistent model.

In the context of various models for the early evolution of a solar nebula, the possible roles assigned to ambient magnetic fields and the paleointensities required to establish the stable natural remanent magnetization (NRM in range 10-4 to 10-1 cgsm) observed in meteorites, are discussed. It is suggested that the record of paleofields present during condensation, growth, and accumulation of grains is likely to have been preserved as chemical (CRM) or thermochemical (TCRM) remanence in unaltered meteoritic material. This interpretation of the meteoritic NRM is made plausible by experimental and theoretical results from the contiguous fields of rock magnetism, magnetic materials, interstellar grains, etc. Several arguments (such as the anisotropy of susceptibility in chondrites, suggesting alignment of elongated ferromagnetic grains, or the characteristic sizes and morphology of carrier phases of remanence, etc.) as well as general evidence from meteoritics (cooling rates, chemical and mineralogical data) can be used to challenge the interpretation of NRM as thermo-remanence (TRM) acquired on a “planetary” parent body during cooling of magnetic mineral phases through the Curie point in fields of 0.2 to 0.9 Oe.

Fine-particle theories appear adequate for treating meteoritic remanence, if models based on corresponding types of permanent magnet materials, e.g., powder-ferrites for chondrites; diffusion hardened alloys for iron meteorites, are adopted, as suggested here.

Finally, a potentially fruitful sequence of experiments is suggested for separating the useful component of NRM in determining the paleofield intensity and its time evolution.
Current Evolution of Meteoroids
Authors: Dohnanyi J. S.
Published: July 2016

The observed mass distribution of meteoroids at 1 AU from the Sun is briefly reviewed in a survey that ranges over the bulk of the mass spectrum from micrometeoroids to meteorite parent objects. The evolution of meteoroids under the influence of collisions, planetary perturbations, the Poynting-Robertson effect and radiation pressure is then discussed.

Most micrometeoroids are expelled from the solar system by radiation pressure shortly after their production as secondary ejecta during impact by larger objects or as dust ejected by comets. Particles that survive will eventually be swept out by the Poynting-Robertson effect.

Meteoroids in the radio and photographic ranges are destroyed in collisions faster than they can be replaced by the production of secondary fragments during collisions between larger objects. The source of new particles needed to maintain the population of these meteoroids in a stationary distribution may be material expelled by comets.

The survival of large objects is limited by gravitational scattering during close planetary encounters and by collisions as well, if they spend sufficient time in the asteroid belt. The observed radiation-exposure ages of chondrites are shown to be consistent with this model.
Abundance Distributions in Barred Galaxies
Authors: Roy Jean-René
Published: July 2016

I review the evidence for global abundance gradients in barred galaxies to be flatter when compared with those of normal galaxies. The finding that the abundance gradient becomes flatter as the strength of the bar increases, illustrates the effectiveness of radial flows induced by bars at transporting large amount of gas across galaxy disks.
Tidal Enhancement of Internal Structures
Authors: Chatterjee Tapan K.
Published: July 2016

Observational evidence indicates that the frequency of internal structures (such as rings, bars, spirals, etc.) is preferentially enhanced for spirals in binary systems (e.g. Elmegreen et al. 1990). In this context we study the tidal effects produced due to two spiral galaxies in a near grazing relative orbit with a near parabolic relative velocity, as such barely bound encounters are the most frequent ones. Both the spirals are endowed with an inner and an outer ring.

The spiral galaxies (of radius R) are modeled by an exponential disk of scale length α = 4/R, with a (static) thickness (Chatterjee 1990), and a spherical polytropic bulge (n=0, 3, 4 equally weighted combination) containing 1/3 of the mass; about 10% of the mass of the disk contains gas particles. Two polytropic rings (n=1; Ostriker 1964), are projected on the disk at 1/4 (inner) and 3/4 (outer) of its radius. Though the rings are gaseous, they are here treated as density enhancements. The gravitational potential is softened with softening constants of ∊ = r∘/5, r∘/3, and 0.8r∘, for the bulge, stellar and gaseous components of the disk, respectively. Here r∘ is the radius containing 75% of the total mass of the spiral. The softening constant for the polytropic rings is 0.35, while the mutual gravitational interaction is softened with a softening constant of r∘/4.
The Distribution of Neutral Atomic Hydrogen in the Interacting Ringed Barred Spiral NGC 5850
Authors: Higdon James L. , Buta R.
Published: July 2016

NGC 5850 is a large, nearby SB(r)b spiral that is an apparent member of the NGC 5846 group of galaxies (de Vaucouleurs 1975; Turner & Gott 1976). The mean corrected redshift of this group is ≈1900 km s−1 (Haynes & Giovanelli 1991). We have obtained broadband imaging and VLA HI interferometry of this galaxy as part of a general study of its properties. The most noteworthy characteristic of the galaxy is a severe distortion of the outer regions. This distortion is most likely due to an interaction with another member of the group, possibly NGC 5846 or its companion NGC 5846A, which are only 10' to the northwest. In this paper we summarize some of the results of the optical and HI analysis, and highlight the effects of the interaction.
An HI Study of Two Barred Spiral Galaxies
Authors: Moore E. M. , Gottesman S. T.
Published: July 2016

We have made HI observations of an early type, NGC 1398 (SBab(r)I), and a late type barred system, NGC 3319 (SBc(s)II.4). NGC 1398 is a beautifully symmetric galaxy with a bright stellar bulge, bar and inner ring and tightly wound spiral arms (also classified as an R1 double outer pseudoring). In HI the spiral structure is strong but the center shows a sharp depletion. In contrast, NGC 3319 has an asymmetric appearance and irregular spiral structure. It is rich in its central HI with a gas bar and spiral arms, both of which are highlighted by prominent HII regions. We attempt to determine the pattern speeds of the galaxies and to explore the differences between early and late type systems.
Nature of the Requirements for Reference Coordinate Systems
Authors: Lundquist C. A.
Published: July 2016

The current need for more precisely defined reference coordinate systems arises for geodynamics because the Earth can certainly not be treated as a rigid body when measurement uncertainties reach the few centimeter scale or its angular equivalent. At least two coordinate systems seem to be required. The first is a system defined in space relative to appropriate astronomical objects. This system should approximate an inertial reference frame, or be accurately related to such a reference, because only such a coordinate system is suitable for ultimately expressing the dynamical equations of motion for the Earth. The second required coordinate system must be associated with the nonrigid Earth in some well defined way so that the rotational motions of the whole Earth are meaningfully represented by the transformation parameters relating the Earth system to the space-inertial system. The Earth system should be defined so that the dynamical equations for relative motions of the various internal mechanical components of the Earth and accurate measurements of these motions are conveniently expressed in this system.
Variations of the Angles Between the Plumb Lines of the Astronomical Instruments
Authors: Mironov N. T.
Published: July 2016

Systematic latitude and time observations at points A1, A2,…, Anon the Earth’s surface are capable of giving variations ot the angles between the plumb lines at these points or the arcs Sijconnecting the zeniths of these points. The variations may be both real and spurious. The former are due to crustal movements, variations in the direction of gravity, etc. The latter may result from errors of the adopted proper motions of observed stars and certain instrumental errors. The variation ΔSij. is completely independent of the polar motion and changes in the speed of the Earth’s rotation.
Definition of the Celestial Reference Coordinate System in Fundamental Catalogues
Authors: Fricke W.
Published: July 2016

The celestial reference coordinate system in fundamental catalogues is defined by the position of the celestial equator as the fundamental plane, the vernal equinox as zero point for reckoning right ascensions, and by adopted values of precession. Discussed are (1) the methods which, in practice, provide the equator, equinox and precession, (2) the prospects of progress in the direction of higher accuracy, (3) the realization. of a homogeneous system on the sky, and (4) the extension of the system to a reference frame represented by extragalactic objects.

The basic observational material available for the project of an improvement of the Fourth Fundamental Catalogue (FK4) is discussed, and the plan of establishing FK5 outlined.
Systematic Differences between Global or Local Solutions of Polar Motion Derived from Astronomical and Spatial Measurements
Authors: Capitaine N. , Feissel M.
Published: July 2016

Global determinations of polar, motion are now made by two kinds of methods: the astronomical method as used by the International Polar Motion Service (IPMS) (Yumi, 1973) or by the Bureau International de l’Heure (BIH) (Guinot, Feissel and Granveaud, 1971), and the method based on Doppler measurements on artificial satellites as used by the Dahlgren Polar Monitoring Service (DPMS) since 1967 (Anderle,1970). In addition, there are local methods used to compute the latitude variations of isolated stations from laser or Doppler measurements.
The Application of Radio Interferometers in Astrometry
Authors: Gorgolewski S.
Published: July 2016

An account is given of the recent precision measurements of position of radio sources by VLBI and especially phase-stable interferometer systems of the 5 km radio telescope in Cambridge.

A brief description of the 5 km. telescope is given as well as some of the remarkably accurate determinations of declination and right ascension of radio sources related to the PK4 catalogue. The monitoring of UT1 with high accuracy has also been achieved with the 5 km telescope.

Some prospects of even better accuracies with phase-stable interferometers – and VLBI techniques are also presented.
1.1.9. OSO-5 Zodiacal Light Measurements 1969-1975
Authors: Burnett George
Published: July 2016

The Minnesota zodiacal light experiment on board OSO-5 was reactivated in July of 1974, after having been off for 1-1/2 years and operated successfully through August 1975 at which time the satellite was again turned off. This gives another yearte worth of data to compare with that taken by the same experiment from January 1969 to January 19731,2,3. This paper reports on the seven year comparison.
1.1.14 Measurements of the T-Corona from Daily OSO-7 Observations
Authors: Howard R. A. , Koomen M. J.
Published: July 2016

The white light corona (K + F) between 3 and 10 Rs was observed from October, 1971 through June, 1974 by the NRL coronagraph orbiting on 0S0-7. Daily images from October, 1971 through December, 1972 have been calibrated to yield the daily variation of the coronal brightness as measured through a segmented polarizing plate. This plate had segments of tangential and radial polarization which enabled the separation of the observed brightness into its polarized and unpolarized components at about 5 and 7 Rs. Each image was scanned at 35 heights above the solar limb between 3 and 10 Rs and at every 1° in heliographic position angle. The brightness of selected points in the corona was plotted to obtain the time history of the variations. Curvilinear regression of the radial brightness distributions for each month shows fluctuations in the gradient, magnitude and standard deviation from regression associated with solar activity. Taking means over the entire set of observations yields curves representing the average, the minimum and the maximum coronal brightnesses. The minimum curve derived for each position angle is interpreted as an upper limit of the F coronal brightness. The equatorial minimum curve agrees extremely well with the F model of Saito (1970) in both shape and absolute value after a corrector for stray light has been subtracted. However the minimum curve for the polar regions lies approximately 3 standard deviations (30%) below that for the equator. This implies that the F-corona is not independent of azimuth or alternatively, the minimum equatorial curve may contain a contribution from the K-corona.
2.2.2 The Size Frequency Distribution and Rate of Production of Microcraters
Authors: Morrison D. A. , Zinner E.
Published: July 2016

Crater size frequency distributions vary to a degree which probably cannot be explained by variations in lunar surface orientation of the crater detectors or changes in micrometeoroid flux. Questions of sample representativity suggest that high ratios of small to large craters of micrometeoroids (e.g., a million 1.0 micron craters for each 500 micron crater) should be the most reliable. We obtain a flux for particles producing 0.1 micron diameter craters of approximately 300 per cm2 per steradian per year. We observe no anisotropy in the submicron particle flux between the plane of the ecliptic and the normal in the direction of lunar north. No change in flux over a 106 year period is indicated by our data.
2.3.4 Extraterrestrial Particles in the Stratosphere
Authors: Brownlee D.E. , Tomandl D.A. , Hodge P.W.
Published: July 2016

Over the past several years we have collected 2µm to 30µm particles from the stratosphere using high volume air sampling techniques. In 1970 and 1971 we flew balloon experiments to 34 km, sampling particles from 1.1 × 104m3of ambient air. Beginning in March 1974 we have flown 100 hours of sampling time on a NASA U-2 aircraft yielding a sampling volume of 9.3 × 104m3. In both programs particles are collected by inertial deposition from a 200 ms−1airstream on to clean surfaces coated with thick films of 500,000 centistokes silicone oil.
3.7 Predicted Favorable Visibility Conditions for Anomalous Tails of Comets
Authors: Sekanina Zdenek
Published: July 2016

It was shown elsewhere (Sekanina, 1974) that the observability from the earth of an anomalous tail (antitail) of a comet can be rather straightforwardly predicted from the dynamical and geometric conditions. The physical presence or absence of the antitail at a precalculated time is then a measure of the comet’s production rate, at the relevant emission times, of relatively heavy dust particles (mostly of submillimeter size) that constitute such an antitail. Because the large grains are e-mitted from the nucleus at very low velocities (typically meters or tens of meters per second), an antitail is essentially a two-dimensional formation in the orbit plane of the comet and can be recognized best when projected edge-on, i.e., when the earth crosses the nodal line of the comet’s orbit. In general, however, this condition is not essential for the recognition of antitails (cf., e.g., Comet Kohoutek 1973 XII).
4.10 Expected Distribution of Some of the Orbital Elements of Interstellar Particles in the Solar System
Authors: Belkovich O.I. , Potapov I.N.
Published: July 2016

A two-dimensions distribution p(e,q) of eccentricities e and perihelion distances q can be derived by means of the formula for the probability transformation:
6.1 The Zodiacal Light
Authors: Elsässer H.
Published: July 2016

As one of the most important results of what we heard in these days I consider the density law of interplanetary dust derived from zodiacal light observations by the deep space probes going out to Jupiter and going in to 0.3 AU. The dependence on the distance to the sun R seems to be nearly as R-1. This finding is in agreement with a new discussion of ground based observations which was reported by Dumont. The density law was one of the open questions for a long time; for me this represents a break-through.
Seeing Compensation in Photoelectric Area Scanning
Authors: Franz O. G.
Published: July 2016

A method is described which, through the use of an optical image rotator in conjunction with an area scanner, allows the accurate determination of the magnitudes and relative position of the components of a double star even if the angular separation is significantly smaller than the radius of the seeing disk.
Sur Les Systèmes Stellaires Multiples Hu 1399 Et Cor 197
Authors: Mourão R. R. De Freitas
Published: July 2016

In this communication the multiple systems Hu 1399 and Cor 197 have been studied. A deviation of the residuals has been established. The relative rectilinear motion of the components AC of the system Hussey 1399 can be used to obtain information about the invisible companion.
Does The System Theta Virginis Represent A New Class of Pulsating Star?
Authors: Beardsley W.R. , Zizka E.R.
Published: July 2016

Analysis of the radial velocity variation of θ Virginis A has revealed that, superposed on an orbital variation with a period of 17 years, there is present an ultrashort periodic variation of 0.15-day. This secondary cycle is attributed to pulsation. The question of what type of pulsating star θ Virginis A may represent is discussed.