bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exactly What Is Stellar ‘Radial Velocity’?
Authors: Lindegren Lennart , Dravins Dainis , Madsen Søren 
Published: July 2016

AbstractAccuracy 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

AbstractPrecise 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

AbstractSeveral 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

AbstractThe 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

AbstractWe 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

AbstractConvective 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

AbstractA 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

AbstractRadial 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.
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)
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.
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.
Nature of the Requirements for Reference Coordinate Systems
Authors: Lundquist C. A. 
Published: July 2016

AbstractThe 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.
Definition of the Celestial Reference Coordinate System in Fundamental Catalogues
Authors: Fricke W. 
Published: July 2016

AbstractThe 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.
The Application of Radio Interferometers in Astrometry
Authors: Gorgolewski S. 
Published: July 2016

AbstractAn 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.
2.2.2 The Size Frequency Distribution and Rate of Production of Microcraters
Authors: Morrison D. A. , Zinner E. 
Published: July 2016

AbstractCrater 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.
Sur Les Systèmes Stellaires Multiples Hu 1399 Et Cor 197
Authors: Mourão R. R. De Freitas 
Published: July 2016

AbstractIn 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

AbstractAnalysis 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.
Concluding Remarks
Authors: Kino Ivan R. 
Published: July 2016

It is a great honor to be asked to summarize a conference such as this one, but it is also an impossible task. For a summary I refer you to the table of contents; what I will do here instead is to offer some personal impressions of what we have been doing.My initial feeling was that of an outsider; I have never worked in the field of double and multiple stars, to which many of you have devoted your careers. Yet this meeting has impressed me with the interrelationship of our areas. In this room, are astronomers who represent and have discussed celestial mechanics, stellar dynamics, stellar spectroscopy, and the astrophysics of star formation. I have not counted heads, but we outsiders might even outnumber you hard-core binary-fanciers. And this is, in some sense, a measure of the value of this meeting, and, even more pointedly, of the value of your work: how much does it matter to the rest of us? Every astronomer should ask himself—particularly when the technicalities get thickest— “What am I doing this for?” The answer is emphatically not merely that this particular work is interesting to do. The appeal of astronomy is not in the bricks and mortar that each of us prepares, but rather in the architecture of the structure that we build with those materials. The questions that we really pursue are not the orbits of binaries, nor the structure of star clusters, but rather the basic problems of the universe: how and why are stars made, and why do they develop as they do?
Solar Motion with Respect to the Nearest Galaxies
Authors: Vaucouleurs G. de , Peters W.L. , Corwin H.G. 
Published: July 2016

AbstractSolutions for solar motion with respect to 12 classical members of the restricted Local Group and 9 additional proposed members of an extended Local Group, all within 2 Mpc, suggest that the Local Group – both restricted and extended – is expanding at a rate, H* = 47 ± 12 ou 57 ± 11 km s-1 Mpc-1, which is significantly lower than its free-space (asymptotic) value Ho ≃, 90 km s-1 Mpc-1, as required by the rotating-expanding model of the Local supercluster. The differential rotation effects predicted by the model are detectable in the velocity residuals with correct phase L*o = 87° and amplitude A* = 30 to 40 km s-1 Mpc-1 in the first-order expansion.V = H*r + V⊙ cos A + A* r sin 2(L-L*o) cos2BThe solar motion with respect to the velocity centroid of the Local Group is V⊙ = 340 ± 18 km s-1 toward the apex 1 = 105° ± 5°, b = -11° ± 3°. With the conventional values of the solar motion within the Galaxy the apex of the galactic center in the Local Group is at supergalactic coordinates L = 325° ± 11°, B = -12° ± 11° with a velocity VG = 140 + 25 km s-1.The residual velocity dispersion σ = 40 to 50 km s-1 implies a virial theorem mass VT ≃ 9 x 1011⊙ not significantly in excess of that which can be accounted for by the member galaxies and intergalactic gas clouds.
Anomalous Hubble expansion in inhomogeneous cosmological models
Authors: Mavrides Stamatia 
Published: July 2016

RésuméLes amas ou superamas de galaxies sont assimilés à des condensations en expansion, plongées dans l’univers cosmologique. L’application des résultats déduits de modèles non homogènes en Relativité Générale au cas particulier du Superamas Local permet de rendre compte des observations. Elle montre aussi l’existence de modèles d’amas tels que la lumière qui les traverse présente (pour un observateur extérieur a l’amas) un décalage vers le rouge supplémentaire.
Multi-Wavelength Surveys for Galaxies Hidden by the Milky Way
Authors: Kraan-Korteweg Renée C. 
Published: July 2016

AbstractThe systematic mapping of obscured and optically invisible galaxies behind the Milky Way through complementary surveys are important in arriving at the whole-sky distribution of complete galaxy samples and therewith for our understanding of the dynamics in the local Universe. In this paper, a status report is given of the various deep optical, near infrared (NIR), and systematic blind H I-surveys in the Zone of Avoidance, including a discussion on the limitations and selection effects inherent to the different multi-wavelength surveys and first results.