bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acoustic Penetration and Impact Detector for Micrometeoroid and Space Debris Application
Authors: Kuczera H. , Iglseder H. , Weishaupt U. , Igenbergs E. 
Published: July 2016

AbstractAn active detector is described which recently has been developed for laboratory impact measurements and which already has been proposed for cosmic dust flight experiments. The detector consists of a very thin penetration foil and an impact plate. By means of piezo detectors the elastic-wave propagation times between the impact location and the piezo detectors can be measured in the foil and in the target. The evaluation of these signals gives the time of the event, the impact location, the projectile velocity, the flight path direction and at least the order of magnitude of mass of the impacting particle. This type of sensor will meet all requirements for particle detection in the diameter range from a few microns (dust particles) up to approx. a few millimeters (space debris) at all velocities. Small-sized projectiles can be detected by sensitive amplifiers. Low-energy electronics including data storage can be used for triangulation and impact time calculation. First experimental results which have been achieved in the Munich Accelerator Facilities will be presented.
Complementary Laboratory Measurements of Individual Interplanetary Dust Particles
Authors: Fahey A. , McKeegan K.D. , Sandford S.A. , Walker R.M. , Wopenka B. , Zinner E. 
Published: July 2016

AbstractComplementary analysis techniques including electron microscopy (SEM/EDX and TEM), molecular spectroscopy (FTIR and Raman), and secondary ion mass spectrometry (SIMS), are used to study individual dust particles collected in the stratosphere. Large deuterium enrichments and solar flare tracks show that most particles in the “chondritic” class are interplanetary dust particles (IDPs). Infrared transmission spectra of most IDPs fall into three major classes (layer-lattice silicates, pyroxenes and olivines). TEM and Raman measurements confirm this classification. The IR spectra show certain similarities to spectra observed in comets and protostars. In particular the 6.8 μm features observed in protostars and IDPs may have a common origin. Large D excesses are observed in IDPs of the first two IR classes. The correlation of D/H ratios with the C concentration indicates a carbonaceous carrier of the excess D. The D enrichments and IR spectra provide links to interstellar molecular cloud material.
Physical Properties of Submicronic Carbonaceous Particles Candidate as Cosmic Dust
Authors: Borghesi A. , Bussoletti E. , Colangeli L. 
Published: July 2016

AbstractWe present here a compendium of our laboratory measurements of the physical properties of submicronic particles made by some carbonaceous materials candidate as cosmic dust: amorphous carbon, silicon carbide. Comparison with data obtained by other authors is presented and discussed in view of astrophysical applications.
Microwave and Laser Facilities to Determine Scattering and Colour Signatures Related to the Physical Properties of Dust Particles
Authors: Weiss-Wrana K. , Giese R.H. , Zerull R.H. 
Published: July 2016

AbstractAt Bochum there exist three experimental setups for measurements of the scattering properties of dust particles. The microwave analog experiment is the best choice for systematic studies of particles in the size range between 0.5 and 10 times the wavelength (correspondig to about 0.25 to 5 μm in the optical region). The multicolour laser experiment providing electrodynamic suspension of single dust particles is optimized for studies of particles in the size range between 20 and 150 μm. Another laser experiment is designed for rapid analysis of particle mixtures in view of in-situ applications. The measuring principles of all instruments are shortly summarized.
Preliminary Results of a Dust Scattering Experiment
Authors: Bliek P. , Lamy P.L. , Courtes G. 
Published: July 2016

AbstractAn experimental device, of the nephelometer type, to study the scattering properties of dust particles is presented. A fluidized bed generator produces a continuously flowing aerosol which is illuminated by either a He-Ne laser or a Xenon are lamp with interference filters. The size of the dust particles ranges between 1 and 30 μm. The scattering properties of dust particles are measured in the two directions of polarization. The first results are presented.
Zodiacal Light and the Spatial Density of Interplanetary Grains
Authors: Lamy P.L. , Perrin J.M. 
Published: July 2016

AbstractUsing our model of light scattering by large rough grains, the compatibility of the observed properties of the zodiacal light with models of the spatial density of interplanetary grains is investigated. The agreement is not yet satisfactory and probably calls for further revision of the density distribution function. Our previous conclusion that submicronic grains gives a non-negligible contribution (Lamy and Perrin, 1980) is confirmed.
Wavelength Dependence of the Zodiacal Light
Authors: Schiffer R. , Thielheim K.O. 
Published: July 2016

AbstractWe calculated the scattering cross section of an ensemble of large, convex, randomly oriented particles with a slight surface roughness. If the roughness structure is described by an exponential correlation function, the degree and angular dependence of the zodiacal light reddening are well reproduced by our model.
Equilibrium Temperatures of H2O, Co2 and NH3 Ice Grains in the Solar System
Authors: Crifo J.F. 
Published: July 2016

AbstractThe equilibrium temperatures of spherical grains of pure H2O, CO2 and NH3 ice in the solar system are computed at heliocentric distances ranging from 1 AU out to (> 1500 AU) where solar illumination becomes negligible compared to galactic and extra-galactic light; the grain size range is from submicron to tens of meter in diameter. These results are based on recently published optical constants and on the use of the “complex angular momentum” (CAM) theory for computing the interaction of the grains with light.
The Gravitational Zones of Influence of the Planets Acting on Small Celestial Bodies
Authors: Misconi N.Y. , Rusk E.T. 
Published: July 2016

AbstractTisserand’s definition of the “sphere of action” of a planet is based on the equality of tidal vs. gravitational acceleration ratios of the sun and planet. Öpik and others based their relation on equating the differential solar and planetary forces on a particle. Neither expression was formulated to describe the zone of influence surrounding a planet when considering the small, but significant, long-term perturbative effects of the planets on a particle’s orbital elements. For the purpose of determining these effects on interplanetary dust we derive a zone of influence based on equating the gravitational forces of the sun and planet.
An Analysis of IRAS’ Solar System Dust Bands
Authors: Dermott S.F. , Nicholson P.D. , Burns J.A. , Houck J.R. 
Published: July 2016

AbstractMeasurements of longitudinal variations in the brightness and in the latitude of the solar system dust bands recently discovered by IRAS will determine the orbital elements of the particles involved and may discriminate between cometary and asteroidal models of the origin of these bands. The expected variations for bands of dust particles with common orbital elements and small eccentricity and inclination are calculated as functions of semimajor axis.
Physical Constraints on Models of Gamma-Ray Bursters
Authors: Epstein Richard I. 
Published: July 2016

AbstractThe power per logarithmic bandwidth in gamma-ray burst spectra generally increases rapidly with energy through the x-ray range and does not cut off sharply above a few MeV. This spectral form indicates that a very small fraction of the energy from a gamma-ray burst source is emitted at low energies or is reprocessed into x-rays and that the high-energy gamma rays are not destroyed by photon-photon interactions. The implications are that the emission mechanism for the gamma-ray bursts is not synchrotron radiation from electrons that lose most of their energy before being re-accelerated and that either the regions from which the gamma rays are emitted are large compared to the size of a neutron star or the emission is collimated and beamed away from the stellar surface.
Computer Simulations of Astronomical Phenomena
Authors: Noels A. , Papy R. 
Published: July 2016

The basic idea of this project is to introduce a senior student to an astronomical phenomenon that he analyses carefully and simulates on the graphic screen of a personal computer. In a second step, this simulation serves as a demonstration for junior students.Three examples are presented here: the retrograde motion of the planets, the Earth’s rotation, and the precession and the equilibrium figure of the Earth due to tides. Programs have been written on an IBM PC/AT.It would be highly desirable to start an exchange program of material of didatic interest among the international astronomical community
Process and Practice
Authors: Bishop Jeanne E. 
Published: July 2016

I would like to discuss strategies for participation within planetarium programs. The planetarium is not only a theater in which passive audiences can hear lectures and see demonstrations. It is also a classroom in which people of all ages can benefit from involvement. Participatory programs have been advocated in the US since the early 1970’s, and the idea has grown and spread.One participatory method involves drawing. For example, an elementary school group can draw a planet group for two or three different times. The psychological value of learning by drawing is well known. And drawing positions of stars and planets with appropriate labels produces take-home sky charts. Families can and do use them to learn astronomy and enjoy the sky together.
Teaching Teachers in the Planetarium
Authors: Szostak Roland 
Published: July 2016

Many people do not know what a planetarium is. Since this disappointing fact is even true for well-educated people, including students and teachers, many pupils will never hear about planetariums. In order to spread knowledge about planetariums, universities can play a major role. One of the best ways is to visit a planetarium with students, especially those who will become teachers. Such a visit is a very efficient multiplying factor.But in order to make a planetarium visit efficient, one should not go unprepared. We therefore go with education students who are enrolled in an astronomy course. Before their visit, we inform them about what a planetarium is and about how it is used. We teach them, for example, specific terms of the rotating sky, its coordinates, and the significance of the ecliptic and of retrograde loops. And of course, we teach the students how the sky appears from different latitudes, including the equator and the southern hemisphere. We also teach the technical aspects of how the projector works.
Astronomy for the Visually Handicapped
Authors: Lacombe Pierre 
Published: July 2016

It is important to add that in addition to the general public and all the students and teachers involved in school systems, the planetarium community in general tries also to reach some special groups of the public. The groups could be those with hearing problems, those who have never seen any stars (the visually handicapped), amateur astronomy groups, and even gifted students.As you can imagine, these special groups represent a very small fraction of our attendance at the planetarium but they need special treatment, and for that reason many planeteria around the world have at one time or another prepared a unique program in the star theater for them, built new and special exhibits, or given technical tours of their installations.
Teaching and Popularizing Astronomy in Egypt and other Arab Countries
Authors: Aiad A. 
Published: July 2016

The recent astronomy of the Arab countries began by the last decade of the 19th century in Alger and the first decade of the 20th century in Helwan. Two Arab countries have been members of the IAU, namely Egypt (since 1925) and Iraq (since 1976). Saudi Arabia, Algeria, and Morocco became members in 1988. We restrict ourselves here to the teaching and popularizing of astronomy.In Egypt there is a single department of astronomy; since 1937 it has belonged to the Faculty of Science of Cairo University. A B.Sc. in astronomy requires two years’ study of mathematics and physics followed by two more years devoted mainly to astronomy, including a small project. Elementary courses for other sciences, such as geography and geophysics, are also taught at Cairo University and the American University in Cairo.
Theoretical Modelling of Algol Disks
Authors: Hubeny I. 
Published: July 2016

AbstractA brief review of various theoretical approaches to model accretion disks is presented. Emphasis is given to models that determine self-consistently the structure of a disk together with the radiation field. It is argued that a proper treatment of the vertical structure is essential for calculating theoretical spectra to be compared with observations. In particular, it is shown that hot layers above an accretion disk (sometimes called disk “chromospheres” or “coronae”), whose presence is indicated by recent UV observations of strong emission lines of highly ionized species, may be explained using simple energy balance arguments.
Algols: Wherefrom, Whereto, and What in Between ?
Authors: De Greve J. P. 
Published: July 2016

Abstract.Four different aspects related to the evolution of Algols are discussed: the occurrence of a contact phase during the mass transfer, the evolution of short period systems evolving through case A mass transfer, the influence of the mass transfer on the surface abundances of both components, and the problem of the initial parameters of Algol systems. For the latter, a search is made for conservative case B systems. UZ Cyg seems to be a good candidate for such evolution. Finally, some remarks are given on the initial values of the low mass Algol S Cancri.
The Relation of Algols and W Serpentis Stars
Authors: Wilson R. E. 
Published: July 2016

AbstractEvidence on the issues of whether the W Serpentis stars are a coherent class, and how they may interface with the Algol systems, is reviewed, with emphasis on the idea that they are semi-detached systems in the latter part of the rapid phase of mass transfer, with optically and geometrically thick disks of transferred gas around the (now) more massive star. We are interested in what will be seen when the gas clears away, and mainly examine the idea that it will be an Algol-type system. More particularly, consideration is given to centrifugally limited accretion as a mechanism to build up a substantial disk, and the presumed evolutionary sequence is from a W Ser to a rapidly rotating Algol to a normal Algol system. Systems such as V367 Cyg and RW Tau fit into this scheme only with difficulty. Because it is extremely difficult to measure the rotation of some W Ser (mass) primaries, it is natural to look at the rotation statistics of Algols to test this idea. The badly behaved light curves and spectroscopy of some Algols (eg. U Cep, RZ Set) may be attributable to the double contact condition, and the ramifications of this possibility are discussed. If so, the rotation statistics of Algols should show two spikes, corresponding to the two special conditions into which a system should be driven by tidal braking and centrifugally limited spin-up. Present rotation statistics do show these spikes. Algols should flip between these states fairly quickly, depending on the mass transfer rate. Thus, to the extent that the meager statistics can be accepted as meaningful, the new (fourth) morphological type of close binary (double contact) has attained demonstrable reality. The rotation statistics are presented in terms of a particular rotation parameter, R, which is zero for synchronism and unity for the centrifugal limit. Future work should develop rotation statistics to see if the rotational lobe-filling (R=l) spike persists. It should also look into whether W Ser primaries are on the hydrogen burning main sequence, or in general what they are. We also need more light curves of W Ser type systems, high resolution line profiles for the (mass) primaries (with particular attention to the W Ser-Algol transition cases), and spectroscopy of low inclination W Serpentis systems, such as KX And.
Common Envelope Evolution of Binary Stars
Authors: Livio Mario 
Published: July 2016

AbstractWe discuss the common envelope phase in the evolution of binary systems. The problem of the efficiency of energy deposition into envelope ejection is treated in some detail. We describe the implications of common envelope evolution for the shaping of planetary nebulae with close binary nuclei and for double white dwarf systems, considered to be the progenitors of Type I supernovae.
Who is Who in Algol-Land ? - Part I -
Authors: De Greve J.P. , Packet W. 
Published: July 2016

AbstractWe computed the evolution through case A mass transfer for 8 systems with mass of the primary equal to 3 and 5 Mo, mass ratios 0.7 and 0.9, and different periods. To this we added similar results from Packet (1988) for Mi=9 Mo, qi=0.6, Pi=1.62 d.During the mass transfer two competing mechanisms in the gainer decide on the evolution of the system: the rejuvenation of this star as the increasing convective core mixes fresh hydrogen into the inner regions, and the acceleration of nuclear burning, responding to the increasing mass.In all the cases the net result is a faster decrease of the central hydrogen content compared to the mass losing star. The secondary fills its own critical Roche lobe and reversed mass transfer starts.From our results and those of Nakamura and Nakamura (1984), we find that reversed mass transfer occurs after core hydrogen burning of the secondary (case A1B2) approximately for periods larger than 1 d (Mli=3 Mo) to 2 d (Mli=l3.4 Mo). For smaller periods this happens before the gainer ends its core hydrogen burning (case A1A2).
Absolute Dimensions of Algol Binary Systems
Authors: Garcia J.M. , Gimenez A. 
Published: July 2016

In order to check the evolutionary status and theoretical models of eclipsing binaries of Algol type, a reliable determination of their absolute dimensions is needed. In this communication, we compare the most commonly used methods to derive absolute parametors in single-lined aclipsing binaries. Let us first assume that the mass function, f(m), is known from the analysis of the radial velocity curve while the relative radii and orbital inclination are derived from the light curve. The determination of absolute parameters is then equivalent to the obtention of the mass ratio, q = m2/m1. The following methods are available to estimate q from observed parameters — over-all errors being estimated for observational uncertainties of the order of 5 % in relative radii and temperatures and 15 % in f(m) —:1.qs: It is assumed that the primary component follows the mass-luminosity relation for main-sequence stars. This procedure provides qs with an uncertainty of about 10 %.2.qsD: It is assumed that the secondary component fills its Roche lobe. Errors of at least 15 to 20 % are expected from this procedure mainly due to its high sensitivity to small variations in the observed value of r2, particularly if r2 > 0.2.Both methods can be used together when f(m) is doubtful, or completely unknown, but errors can not be expected to be better than in case 2.3.qn: It is assumed that the primary component rotates synchronously in a circular orbit. This assumption is difficult to adopt due to the expected transfer of angular momentum through mass transfer and the value of qn is estimated with about 20 to 30 % error.4.qED: It is assumed that the primary component, is well reproduced by standard evolutionary models within the main sequence. Adopting a grid of models for a given chemical composition, an iterative procedure in the log Ti,.–log g plane permits the determination of m1 and thus q. This method is equivalent to (1) but avoids errors due to evolution from the ZAMS to the TAMS, not taken into account in the previous method, and allows to reach a higher accuracy, around 5 %, except for those primary stars located around the TAMS, where the determination of mi is not unique.
Binary Statistics and Star Formation
Authors: Zinnecker Hans 
Published: July 2016

AbstractBinary statistics, in particular the distributions of mass ratios and orbital periods, are reviewed in an attempt to obtain clues to possible star formation and cloud fragmentation processes. Various observational selection effects which hamper the establishment of the true distributions are discussed. Four different theories of binary formation are compared (fission, fragmentation, capture, and the disintegration of small star clusters), none of which can be ruled out. We conclude that there may be many ways to form binary systems. The dominant mode of binary formation could be ring fragmentation or disc fragmentation depending upon whether the distribution of mass ratios is found to decrease or to increase towards small mass ratios. Future speckle interferometric measurements of a sufficiently large sample of close visual binaries are suggested to settle this important observational question. The present paper is special in that it brings together a wealth of useful information, both observational and theoretical, in one place.
A Comparison Between Binary Star Light Curves and Those of Possible Binary Asteroids
Authors: Schober H. J. 
Published: July 2016

AbstractSince about ten years coordinated programs of photoelectric observations of asteroids are carried out to derive rotation rates and light curves. Quite a number of those asteroids exhibit features in their light curves, with similar characteristics as variable stars and especially eclipsing binaries. This would allow also an interpretation that there might be an evidence for the binary nature of some asteroids, based on observational hints. A few examples are given and a list of indications for the possible binary nature of asteroids, based on their light curve features, is presented.
A Plan for a New Generation 2 m-Class Telescope in Indonesia
Authors: Van Der Hucht Karel A. 
Published: July 2016

AbstractOne of the prime astrophysical interests of the Observatorium Bosscha is, and has always been, double star research: visual double star research with the double-60 cm Zeiss telescope (dedicated in 1928), and theoretical research of evolved massive spectroscopic binaries (since 1972). For one thing, this is the very reason that this IAU Colloquium No. 80, celebrating the 60th anniversary of the Observatorium Bosscha in Lembang, is devoted to binary astrophysics.Up to now, visual, photographic, and photometric tools have been used for binary research at the Observatorium Bosscha. An important, essential additional tool for binary research is spectrographic equipment, in order to measure radial velocities of binary components.