bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Resolution Imagery and Slitless Spectroscopy at the Prime Focus of the CFH Telescope
Authors: Fouéré J.C. , Lelièvre G. , Lemonier J.P. , Odgers G.J. , Richardson E.H. , Salmon D.S. 
Published: July 2016

AbstractDirect photographic work over a large field (1°) at the prime focus of the classical Canada-France-Hawaii 3.6m telescope has been achieved with a very good image quality (less than 0.5” FWHM). The basic characteristics of the Wide-Field Corrector are presented. Our Wynne Corrector was in fact redesigned to have the last optical surface flat so that a transmission grating could be replicated thereon. This arrangement with only three optical elements locates the gratings at a maximum distance from the focal surface resulting in improved resolution over a one degree field. The C.F.H.T. grating-plus-lens, or “grens” has a brightness limit which is fainter than the Palomar Sky Survey.
The origin of comets among the accreting outer planets
Authors: Greenberg Richard 
Published: July 2016

AbstractThe hypothesis of formation of comets as an accompaniment to formation of Uranus and Neptune from icy planetesimals is attractive for several reasons, but has suffered from long-standing problems regarding formation of the planets themselves. The history of this problem is reviewed, and recent results are described that may help solve it. Numerical simulations of planet growth show that when the system of planetesimals is no longer artificially constrained to a power-law size distribution, growth of planets may occur in reasonable time. An adeguate number of comet-sized bodies to populate the Oort cloud is not produced as collisional debris during the planet-building process. Rather, the comets are probably a remnant of the original planetesimal “building blocks” from which the planets grew.
Dynamical evolution of the Oort cloud
Authors: Weissman Paul R. 
Published: July 2016

AbstractNew studies of the dynamical evolution of cometary orbits in the Oort cloud are made using a revised version of Weissman’s (1982) Monte Carlo simulation model, which more accurately mimics the perturbation of comets by the giant planets. It is shown that perturbations by Saturn provide a substantial barrier to the diffusion of cometary perihelia into the inner solar system; Jupiter also. Perturbations by Uranus and Neptune are rarely great enough to remove comets from the Oort cloud, but do serve to scatter the comets in the cloud in 1/a. The new model gives a population of 1.8 to 2.1 × 1012comets for the present-day Oort cloud, and a mass of 7 to 8 earth masses. Perturbation of the Oort cloud by giant molecular clouds in the galaxy is discussed, as is evidence for a massive “inner Oort cloud” internal to the observed one. The possibility of an unseen solar companion orbiting in the Oort cloud and causing periodic comet showers is shown to be dynamically plausible but unlikely based on the observed cratering rate on the earth and moon.
The formation and evolution of meteor streams
Authors: Williams I.P. 
Published: July 2016

AbstractThe physical processes which may affect the evolution of meteor streams are discussed and a review is then given of the work carried out to date on the evolution of meteor streams. It is clear that they evolve principally due to the effect of planetary perturbations and radiation pressure. The formation of streams from the breakup of a comet is also discussed. All the evidence, including the recent, discovery of 1983TB points to the correctness of this hypothesis.
First results of the integration of motion of short-period comets over 800 years
Authors: Carusi A. , Kresák L. , Perozzi E. , Valsecchi G.B. 
Published: July 2016

AbstractAll the known short-period comets have been followed by numerical integration over a time span of 821 years, from 1585 to 2406. A preliminary survey of the results of these integrations has shown some interesting features, which become recognizable thanks to the length of the time interval covered, not negligible if compared with the typical evolutionary time scale of comets moving in short-period orbits. Interesting phenomena that have been recognized include: (1) captures from, or ejections into, very elongated ellipses, with perihelia of the parking orbits close to the orbit of Jupiter and aphelia within or beyond the region of outer planets; (2) passages of comets from the control of Saturn to that of Jupiter; (3) orbital evolutions controlled mainly by Saturn; (4) librations of comets around low-order resonances; (5) repeated close approaches of comets to Jupiter, often with the comet being captured as a temporary satellite; (6) an almost perfect coincidence of two comet orbits just before a close approach to Jupiter, suggesting their genetic relationship.
A study of the pre-discovery motion of the two asteroids 1983 SA and 1983 XF
Authors: Benest Daniel , Bien Reinhold , Rickman Hans 
Published: July 2016

AbstractOur investigation demonstrates that the asteroidal objects 1983 SA and 1983 XF can be considered as temporary visitors of the 4/3 and 2/1 resonance with Jupiter, respectively. Evidence is given that both objects are first rank candidates for a cometary origin. The case of 1983 SA is remarkable in so far as (279) Thule is up to now the only known asteroidal 4/3 librator.
Balloon Observation of the F-Corona at the 1983 Total Solar Eclipse
Authors: Isobe S. , Tanabe H. , Hirayama T. , Koma Y. , Soegijo J. , Baba N. 
Published: July 2016

AbstractA balloon observation of the F-corona in visual and infrared regions was carried out by Japanese and Indonesian teams at the total solar eclipse on June 11, 1983, in Java, Indonesia. For the visual observation, a SIT television camera, with 4 interference filters (5300Å, 6000Å, 7200Å and 8000Å) and a 45°-step rotating polarizer, was used. The camera measured brightness distributions in a sky area of 5°×5° centered at the eclipsed sun at each polarizer position for each filter. In this paper, a part of results, which are the brightness and polarization distributions in a half area of the 6000Å picture, is shown.
The LDEF Interplanetary Dust Experiment
Authors: Singer S.F. , Stanley J.E. , Kassel P. 
Published: July 2016

The Long Duration Exposure Facility was launched for the first time on April 6, 1984 by the NASA space shuttle Challenger. An array of solid-state detectors record the arrival time and approximate direction of an impacting particle. Two levels of detector sensitivity provide an indication of particle energy and mass. The active area is nearly 1 m2. We therefore expect count rates of about 30 per day over an exposure time of about a year. The orbit of the particle cannot be obtained, except statistically. We know the orientation of the detector, the position of LDEF in earth orbit, and the position of the earth in relation to other celestial bodies. From this information we can extract essential orbit information.An earlier flight on the Explorer 46 satellite gave first evidence of the existence of submicron-sized particles, mostly associated with fresh meteor streams. We hope to obtain more precise data and estimate lifetimes in interplanetary space.To study the fate and origin of IP (interplanetary) dust, we measure various kinds of time variations. Among the most interesting is the secular variation, i.e., the flux in various meteor streams, as a function of the passage of a comet.One of the challenging problems will be to distinguish IP dust from man-made space debris. The separation will depend on knowing something of the orbits of debris. Probably more important will be the chemical analysis of the particles. The two types of information are in a sense complementary.
Observation of High 3He/4He Ratio in Ocean Sediments — Evidence for Extraterrestrial Material Contamination
Authors: Ozima M. , Takayanagi M. , Zashu S. , Amari S. 
Published: July 2016

AbstractOccurrence of anomalously high 3He/4He ratio (> 5 × 10−5) is rather common in the Pacific deep sea sediment. The 3He/4He ratio correlates well with the 3He content, whereas the 3He content shows approximate inverse relation with the sedimentation rate. Input of stratospheric dust of about 1 ppm or less which corresponds to about 2000 ton/y fallout rate can explain the above observation.
Electrostatic Charge of Interplanetary Dust Grains: New Results
Authors: Lamy P.L. , Lefevre J. , Millet J. , Lafon J.P. 
Published: July 2016

AbstractA continuing program aimed at improving the determination of the charge of interplanetary as well as cosmic grains is presented. Recent data have been combined to generate two high-resolution solar spectra corresponding to the maximum & minimum of activity. The energy distribution of photoelectrons emitted by quartz grains under solar irradiation is calculated using the new laboratory measurements of Quemerais et al. (this volume). Finally, the method of Lafon, Millet and Lamy (Astron. Astrophys., 95,295, 1981) is used to find the electrostatic potential of these grains.
Secondary Emission from Interplanetary Dust Grains
Authors: Millet J.M. , Lafon J.P. 
Published: July 2016

AbstractSecondary emission can play an important role in the charging of dust grains. This process is very sensitive to their size and to the physical properties of the solid. It is particulary important in the case of insulators in which an intense electric field is present at the surface and can accelerate the excited electrons.As a consequence, the secondary emission yield δ does not depend on the energy of primaries and multiple solutions of the potential due to the usual non-monotonic form of δ versus the energy of primaries disappear.
Effect of Two Types of Non-Maxwellian Electron Distributions on Temperature Spectroscopic Diagnostics
Authors: Möller C. , Lamoureux M. 
Published: July 2016

Continuum emission due to bremsstrahlung and direct radiative recombination is studied in two types of fusion-plasmas with non-Maxwellian electron distributions. The calculated emissivity coefficients Jω(hω) are shown to depart from the Maxwellian ones. The main consequence of the modification of the spectrum is to invalidate the usual electron temperature diagnostic which consits in equating dlnjω(hω)/d(hω) to l/kTe.Case I corresponds to the critical density region of a laser-produced plasma ( Langdon 1980, Mora and Yahi 1982 ). The distribution function is cm exp (-v/vo,m)m with m=5 for all values of the incident electron velocity v. Case II corresponds to very steep temperature gradients for which the spacial scale of the transport region is larger than the gradient scale itself (Albritton 1983, Luciani et al. 1984, Campbell 1984). On the higher temperature side of the heat front, the tail of the distribution is depleted with respect to the Maxwellian one. At a particular distance from it, this tail can be roughly described by the above analytical function but with m=3.
Recombination Lasers in the XUV Spectral Region
Authors: Pert G.J. 
Published: July 2016

In a conventional laser operating in the near ultra-violet, optical or infra-red spectral bands the photon energies, not exceeding lOeV, are closely matched to the electronic or molecular energy levels of neutral and weakly ionised atoms. Consequently typical photon energies (~ eV), and transition lifetimes (~ ns) closely match the characteristics of fast electrical circuitry feeding a weakly ionised discharge which may be used to pump either directly or indirectly the laser medium.In a X-ray laser operating at about 10Å, photon energies are about 1 keV, and lifetimes about 10−14s (l0fs). In consequence the power required to pump the laser must be expected to increase rapidly as the wavelength decreases. The gain per unit length is given by:where ζ is the line shape factor, A the spontaneous transition probability, λ the wavelength, and Δν the width of the line, and (n2,g2) and (n3,g3) the population density and statistical weight of the lower and upper laser states respectively. The total power loss per unit area, p, of the medium must exceed that emitted by spontaneous decay of the laser transition.
XUV Spectra of Ag XVII - Ag XXI and Cd XVIII - Cd XXII from Laser Produced Plasmas
Authors: Khan M.A. , Al-Juwair H.A. , Tallents G.J. 
Published: July 2016

The spectra of highly ionized Ag and Cd in the region 20–200 Å excited in laser produced plasmas were recorded and analyzed. The spectral lines identified correspond to Ag XVII - Ag XXI and Cd XVIII -Cd XXII involving transitions of the type 3dk n1 – 3dk nl' and 3dk – 3dk−l nl" where k = 9,10; n = 4,5,6; 1 = s,p,d,f; 1' = s,p,d,f,g, and 1" = p,f.The experimental work was carried out at the Australian National University Research School of Physical Sciences. The Nd=glass laser system delivered pulsed powers of the order of 1015W/cm2 onto flat metalic targets placed in a vacuum. The target could be positioned accurately in the focal plane of the input lens. The spectra were recorded photographically on Kodak SC5 plates with a 2-m grazing incidence spectrograph (Hilger & Watts E-580) employing a 600 lines/mm grating at 88.157° incidence. A maximum of three laser pulses gave the desired plate exposure while a single shot exposure from a pure carbon target plasma provided the reference points for wavelength calibration. The well-known Lyman spectra of CVI and CV appeared strong and could be clearly identified upto their 5th order. The wavelengths of some strong lines of Ag XIX and Cd XX previously measured (1) were used as secondary wavelength standards and a best fit was then made with the wavelengths computed from the dispersion equation of the grating. The accuracy of the measured wavelengths was within 0.02A° and better than 0.005A° at points closer to the reference lines.
Novae and Accretion Disc Evolution
Authors: Bath G.T. 
Published: July 2016

AbstractAt outburst the classical nova generates an extended optically-thick wind driven by radiation pressure in the continuum. At maximum light the optical luminosity is close to the Eddington-limit. The subsequent decline illustrates the interaction between radiation and matter in a wind which gradually thins as the mass loss rate falls at an approximately constant Eddington-limit luminosity. As the wind thins so the effective photosphere shrinks back into the underlying binary, and an increasing fraction of the radiation is emitted at ultraviolet wavelengths. Model atmosphere computations show how the increasing flux of ultraviolet photons is associated with the shell becoming more and more ionized through radiative ionization. Attempts to study the internal structure of the wind confirm that the luminosity must be close to the Eddington limit and must be expelled from close to the white dwarf surface. It is generally agreed that the outbursts are caused by runaway nuclear burning of accreted material at the white dwarf surface, but it is possible that some events of the classical nova type may be caused by runaway accretion at a super-critical rate.In dwarf novae very different behaviour is evident. The outbursts are located within the accretion disc and are generated either by mass-transfer bursts due to dynamical instability of the Roche-lobe filling star, or by an instability within the disc itself. In either case the eruption behaviour is due to an enhanced accretion flux through the accretion disc. One important aspect of the radiation hydrodynamics is the luminosity generated by impact of the mass-transfer stream with the accretion disc and penetration by the stream within the disc. Attempts at examining this penetration region are described and results compared with observed behaviour of disc evolution through the course of an outburst. The possibility that disc instabilities will not propogate in realistic discs which deviate from axial symmetry is considered.
Graduate Astronomy Studies at The University of São Paulo, Brazil
Authors: Maciel Walter J. 
Published: July 2016

The University of São Paulo (USP), founded in 1934, is the largest university in Brazil, having about 50,000 students and 5,000 teachers/researchers distributed among 33 institutes and 184 departments.Astronomical work was already developed at the older São Paulo Observatory (founded 1912), which was later attached to the university. The observatory has been renamed as Instituto Astronômico e Geofisico (IAG), and presently houses the departments of Astronomy, Geophysics, and Meteorology. Graduate astronomy courses, intended to provide Master (M.Sc.) and Doctor (D.Sc.) degrees, started in 1973.
Comparative Methods for Teaching an Astronomical Topic
Authors: Isobe Syuzo 
Published: July 2016

Astronomy has greatly progressed in this decade. The number of people who are interested in astronomical phenomena is certainly increasing as the number of IAU members increases. These people are divided into several categories, depending on their degrees of interests. For Japan, these are as follows:The situation is changed when some such special event, such as a return of Halley’s comet, occurs. We can say that our present target in teaching astronomy is to increase the number of people in each category except the last one.
The Personal Computer for Teaching Astronomy
Authors: Andreoni R. , Forti G. , Ranfagni P. 
Published: July 2016

The two interactive software packages, which we called ASTRONOMIA 1 and ASTRONOMIA 2 (in the following Al and A2) and developed for a personal computer under MS-DOS, are primarily intended to be used in junior-high and high schools as tools for teaching astronomy. With the help of these programs and using the sky as a laboratory, the teacher can explain the most difficult parts of the astronomical geography: time and coordinates. Very few schools in Italy own the necessary educational tools such as a small planetarium, a sidereal clock, an oriented celestial sphere, etc.We tried to exploit the capability of a personal computer to visualize and to present the results of a calculation as diagrams and tables. A limited interaction permitted by the programs allows the user to compare the results with other computations.
Informative Slide Sets in Astronomy
Authors: Fraknoi Andrew , Harrington Sherwood 
Published: July 2016

In astronomy, perhaps more than any other science, the cliché is true: A picture can be worth a thousand words. Unfortunately, with the illustrations in some astronomical textbooks, a picture can sometimes require a thousand words. And for beginning or inexperienced instructors, the worst thing can be that a picture may deserve a thousand words, but the instructor has only 50 words at his or her disposal.Even for experienced instructors, unless the image happens to be in one’s own area of expertise, it can sometimes be difficult to appreciate or convey the full significance of a modern deep-sky photo, radiograph, or satellite multicolor composite image.
Public Misconceptions about Astronomy
Authors: Acker A. , Pecker J.-C. 
Published: July 2016

The Chinese proverb quoted above means more or less the same thing that our Rabelais did in the middle of the Renaissance, when his famous Gargantua made the statement: “well built brains are to be preferred to overfed brains.”Indeed, when facing the fallacies that invade our modern life, and when facing the very quickly changing world in which we evolve, it seems that the only weapon we can give is a critical approach to science and life. We feel that anyone can assess at least the likelihood of any alleged fact, or, if he cannot, that he should be able to recognize openly his inability to do so.Now let us consider the common fallacies of modern times. And you will excuse me if I come back several times to the same motto, from my old Rabelaisian education....
Teaching Astronomy at Keio Senior High School, Japan
Authors: Tsubota Yukimasa 
Published: July 2016

The major problem in teaching astronomy in our senior high schools has to do with the nature of the Japanese educational system. The typical science curriculum consists of physics, chemistry, biology, earth science, and general science I & II. The Japanese Ministry of Education allows General Science I to fulfill the minimum high-school graduation requirement in science. General Science I covers the basics of earth science. Astronomy has been taught as a part of General Science I and Earth Science.Many Japanese high schools do not offer earth science because it is not covered in the college entrance exams (Table l). Moreover, teachers usually spend many hours with the students memorizing the basics of earth science rather than allowing some time in the laboratory.
Strategies for Presenting Astronomy to the Public
Authors: Sweitzer James S. 
Published: July 2016

Imagine an American trying to explain a triple play to someone who understands English poorly and who has never seen a baseball diamond, much less a game. Yet this is the sort of challenge astronomy educators face every day both in the classroom and in more informal settings.In a college classroom, the professor has some time to teach students the language of science and astronomy. As the students gain proficiency, they can then comprehend increasingly complex concepts. Through repeated classroom exposure and study, eventually most students learn the basics of astronomy.
Innovative Astronomy Education Programs for Developing Countries
Authors: Sidharth B.G. 
Published: July 2016

It is desirable that planetariums in developing countries should make the maximum and most efficient use of the planetarium infrastructure and facilities to cover as much ground as possible in the popularization and dissemination of astronomy. After all, the number of planetariums in developing countries necessarily has to be small, and so specialization in specific disciplines or fields becomes a luxury. In India, for example, there are about ten planetariums, and another five or six will come into operation in the next few years. But these planetariums have to cater to a large population. In the U.S.A., which has a fraction of India’s population, on the other hand, there are hundreds of planetariums. The following suggestions are based on successfully implemented projects at the B.M. Birla Planetarium, Hyderabad.A golden rule for planetarium programs anywhere, and certainly in developing countries, is to start a planetarium sky show or activity with a local flair. For example, the local names of stars and constellations, local myths, local astronomers or, more specifically, topics like the history of astronomy in the region should be highlighted.
Algols as Limits on Binary Evolution Scenarios
Authors: Hjellming M.S. 
Published: July 2016

AbstractEvolutionary scenarios must account for Algol binaries surviving their first phase of mass transfer. The outcome of this phase is dependent upon the rapidity of the initial mass transfer, which can be estimated by calculating the radial reponse of potential progenitors to mass loss. Limits on the donor’s evolutionary state, and its companion mass, can be placed on systems which would transfer mass on a thermal or dynamical timescale. Slower mass transfer rates are necessary for the successful transition to an Algol. Considering 1.5 and 5.0 M⊙ models, the former succeed in case A and Br systems, while the latter can do so only in case A systems. To evolve into an Algol binary, all systems seem to require initial mass ratios near one.
The Masses and the Radii of the Components of U Cep
Authors: Heintze J.R.W. , van Gent R.H. 
Published: July 2016

This system needs no introduction after the publications of Batten (1974) and of Hall (1975). According to Plavec (1983) the spectral type of the primary is B8 V.Tomkin (1981) obtained simultaneously the radial velocities of the primary (≡ RV1) and the secondary (≡ RV2) of U Cep in the near-infra red, which resulted in the following parameters (in km/s):From the slope of the RVCZ around ϕ= 0, he finds:The (M/M⊙ ; R/R⊙ ) values as published by Tomkin are (4.2; 2.7) for the primary and (2.6; 4.9) for the secondary.