bluuebunny/crossref_metadata_2025_split huggingface dataset:
Volume-Limited Spectroscopic Binary Statistics
Authors: Fisher J. , Schröder K.-P. , Smith Robert Connon 
Published: June 2019

AbstractWe derive the period (P), primary mass (m1) and mass ratio (q) distributions of the local population of field binaries by studying a volume-limited sample of 371 spectroscopic binaries (SBs) in the solar neighbourhood d ≤ 100 pc and Mv ≤ 4. The sample was collated using the Batten catalogue, data of R.F. Griffin and the Hipparcos catalogue. The SB2s are used to calibrate a Monte-Carlo approach to the q distribution of SB1s, giving a total q distribution confirming a peak at q ≈ 1. Completenesses and parameter-specific biases are also assessed. A substantial number of systems with intermediate to long periods are found which may have significant consequences for the mass-distribution of WDs.
The Formation of Binary and Multiple Stars in Clusters
Authors: Bate Matthew R. 
Published: June 2019

AbstractWe discuss theoretical aspects of binary and multiple star formation, focusing on their formation in stellar clusters. First, we review individual processes that may occur during the formation of binary and multiple stars: fragmentation, accretion, interactions with circumstellar discs, and dynamical interactions. We then discuss the results from a recent large-scale hydrodynamical calculation of cluster formation in which all of these processes occur simultaneously, examining the formation mechanisms and resulting properties of the binary and multiple stars in this cluster.
Optical Light Curves of Supernovae
Authors: Leibundgut Bruno 
Published: June 2019

SummaryLight curves are the most readily available and most frequently used astrophysical tools for variable phenomena. Supernovae are no exception to this. The information that can be extracted from detailed light and colors curves, together with the detailed study of the spectral evolution, tells us about the progenitor star, the various energy input sources, the explosion environment, material in the line of sight and cosmological effects. Over the past decade we have come to understand the power of detailed light curve studies and how they tie into the exploration of other astrophysical topics.
Effects of Small-Scale Fluctuations of Neutrino Flux in Supernova Explosions
Authors: Madokoro Hideki , Shimizu Tetsuya , Motizuki Yuko 
Published: June 2019

SummaryWe examine effects of small-scale fluctuations with angle in the neutrino radiation in core-collapse supernova explosions. As the mode number of fluctuations increases, the results approach those of spherical explosion. We conclude that global anisotropy of the neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given.
The Supernova/GRB Connection
Authors: Höflich P. , Baade D. , Khokhlov A. , Wang L. , Wheeler J.C. 
Published: June 2019

SummaryWe discuss the possible connection between supernova explosions (SN) and gamma-ray bursters (GRB) from the perspective of our current understanding of SN physics. Core collapse supernovae (SN) are the final stages of stellar evolution in massive stars during which the central region collapses, forms a neutron star (NS) or black hole, and the outer layers are ejected. Recent explosion scenarios assumed that the ejection is due to energy deposition by neutrinos into the envelope but detailed models do not produce powerful explosions. There is new and mounting evidence for an asphericity and, in particular, for axial symmetry in several supernovae which may be hard to reconcile within the spherical picture. The 3-D signatures are a key to understand core collapse supernovae and the GRB/SN connection. In this paper we study the effects and observational consequences of asymmetric explosions.
The Astronomy Village: Investigating the Universe
Authors: Pompea S. M. , Blurton C. 
Published: June 2019

The Astronomy Village multimedia program is designed to emphasize the process of science as much as its content (Pompea and Blurton, 1995; Pompea, 1996). It was designed for 14 year-old students, but has been used at slightly younger age levels and for older students, including university students. The investigations are flexible enough to be used at this wide variety of levels.In this CD-ROM-based multimedia program, student teams can pursue one of ten research investigations. In each investigation they are guided by a mentor, receive e-mail, hear a lecture in the Village auditorium, and make observations using ground or space-based telescopes in a virtual observatory. The students also process data using the NIH Image image processing program. They keep a detailed logbook of their research activities and can run simulations on stellar evolution as well as manipulate 3-D astronomy visualization tools.
Galactic Distribution, Kinematics, Locations in Clusters and H-R Diagrams, and Duplicity of Be Stars (Review Paper)
Authors: Abt Helmut A. 
Published: June 2019

AbstractThe locations of 143 B0e-B7e III-V stars listed in the Bright Star Catalogue are similar to those of the early-B Gould Belt stars. Therefore the Be stars have roughly the same ages and origins as early B stars. The frequency of runaway Be stars must be less than several percent. The radial velocities of Be stars show primarily the reflex of solar motion and show no evidence for systematically negative velocities attributable to mass-loss effects upon the absorption profiles. The scatter in the residual velocities is such that there is unlikely to be many undetected binaries with orbital amplitudes greater than 10 km s-l. We are unable to state whether or not Be stars tend to occur during the overall contraction stage, but we do observe Be stars in roughly constant frequency in clusters of all ages. About 18% of the field B0-B7 III-V stars are Be stars. Clusters show both lower and higher frequencies that may be real or may be due to different observational techniques. The frequencies and distribution of binary periods for Be stars is the same as for non-emission B stars except for the lack of periods less than 10-1 yr. Statistically the 12 classical Be stars with known orbital elements have mass functions indicating that their secondaries are more massive than neutron stars and their secondary mass distribution is like that of normal B stars. We observe 35 companions for 100 Be primaries, so after correction for undetected companions, it seems likely that most Be stars have companions, mostly with periods of years.
An Example Demonstrating the Potential for Asteroseismology of DB White Dwarf Stars
Authors: Bradley P.A. , Wood M.A. 
Published: June 2019

AbstractWe present the results of a parametric survey of evolutionary models of compositionally stratified white dwarfs with helium surface layers (DB white dwarfs). Because white dwarfs are the most common final end state of stellar evolution, determining their internal structure will offer us many clues about stellar evolution, the physics of matter under extreme conditions, plus the history of star formation and age of the local Galactic disk. As a first step towards determining the internal structure of DB white dwarf stars, we provide a comprehensive set of theoretical g-mode pulsation periods for comparison to observations.Because DB white dwarfs have a layered structure consisting of a helium layer overlying the carbon/oxygen core, some modes will have the same wavelength as the thickness of the helium layer, allowing a resonance to form. This resonance is called mode trapping (see Brassard et al. 1992 and references therein) and has directly observable consequences, because modes at or near the resonance have eigenfunctions and pulsation periods that are similar to each other. This results in much smaller period spacings between consecutive overtone modes of the same spherical harmonic index than the uniform period spacings seen between non-trapped modes. We demonstrate with an example how one can use the distribution of pulsation periods to determine the total stellar mass, the mass of the helium surface layer, and the extent of the helium/carbon and carbon/oxygen transition zones. With these tools, we have the prospect of being able to determine the structure of the observed DBV white dwarfs, once the requisite observations become available.We are grateful to C.J. Hansen, S.D. Kawaler, R.E. Nather, and D.E. Winget for their encouragement and many discussions. This research was supported by the National Science Foundation under grants 85-52457 and 90-14655 through the University of Texas and McDonald Observatory.
Long Period Variables in the Magellanic Clouds and the Galaxy
Authors: Hughes S.M.G. 
Published: June 2019

AbstractNew results (∼last two years) on mainly observational properties of Long Period Variables (LPVs) in the Magellanic Clouds and the Galaxy are reviewed. These properties include the effects of metallicity variations on their mass loss rates, the use of AGB LPVs to map the stellar distributions of the Galactic disk and bulge, and using detailed observations of nearby Miras to investigate their structure and to obtain new parallax distances, with implications for the pulsation mode of Miras.
Nonlinear Models of Miras, Including Time-Dependent Convection
Authors: Ostlie Dale A. , N. Cox Arthur 
Published: June 2019

AbstractNonlinear calculations of Mira variable stars of Population I are presented. Each model is 1 M⊙, with a luminosity of 5000 L⊙ and an effective temperature near 3000 K. These models incorporate our theory of time-dependent convection, which is based on a convective phase lag formalism and includes spatial averaging of convective eddies from adjacent zonal interfaces. The theory also includes turbulent pressure, energy, and viscosity terms and allows for negative convective luminosities in subadiabatic regions where overshooting occurs.Results of the present study suggest that based upon the dynamic behavior of the models, fundamental mode pulsations are the preferred mode of oscillation. In particular, we do not obtain the chaotic behavior that has been noted in previous nonlinear studies of the fundamental mode oscillations of Miras.
The HF Precise Radial Velocity Programme at DAO
Authors: Yang S. , Larson A. , Irwin A.W. , Goodenough C. , Walker G.A.H. , Walker A. , Bohlender D. 
Published: June 2019

AbstractA programme to measure precise radial velocities of late-type stars is being carried out at the 1.22-m telescope of the Dominion Astrophysical Observatory (DAO). Wavelength-calibration fiducials are imposed directly on the stellar spectra by passing the starlight through a controlled hydrogen fluoride (HF) absorption cell placed in front of the coude spectrograph. Presently, the primary targets of the programme are bright G, K, and M giants. Preliminary results confirm the low-amplitude, radial-velocity (RV) variability of the yellow giants discovered at the Canada-Prance-Hawaii telescope using the HF technique. These yellow giants and additional bright candidates are now being continually monitored at DAO. Preliminary results also indicate that the “yellow giant” variability extends to the early-M giants. In addition to the RV variations, the data also yield information on the simultaneous variability of the Ca II λ8662 line, Teff, as well as the R - I index of the stars.
The Extreme UV Spectra of the Dite Tokamak
Authors: Hobby M.G. , Mansfield M.W.D. , Peacock N.J. , Cowan R.D. 
Published: June 2019

The emission spectrum of the Culham Tokamak, DITE, has been photographed between 10 and 300 Å with spatial and, to a limited extent, temporal resolution. The line spectrum throughout this wavelength range has been interpreted in detail. Apart from well known impurity lines of the light elements, 0, N and C, and of metallic ions of Fe, Cr and Ni, the emission spectrum of DITE is found to be overwhelmingly due to high-stripped Mo ions, the identity of which is confirmed from comparisons with a laser-produced plasma spectrum of Mo and with ab initio Hartree Fock calculations.In DITE it has been found that Mo ions with degrees of ionisation ranging from XIV to XXIV and above are present. The Mo spectrum may be broadly divided into two distinct regions. In the first, 65-90 Å, a strong dense band of emission lines is observed. These lines may all be accounted for as 3p → 3d transitions in Mo XVI and higher degrees of ionisation.The second group of Mo lines, between 54 and about 20 Å comprises broad well-spaced bands of emission. The 3d → 4p bands extend below o 35 Å, probably at least as far as Mo XXIV, but are overlapped by other n=3→n = 4 bands, notably 3d → 4f, in lower degrees of ionisation. Inner . subshell transitions are shown to be of some importance in accounting forthe complexity of the merging bands at around 20 Å.
Photometric Monitoring of Binaries in Open Clusters and Associations: NGC 6231
Authors: Sterken C. , Bouzid M. Y. 
Published: June 2019

AbstractOver the last couple of years we carried out long-term CCD monitoring of open clusters and associations with as principal goal the detection and study of pulsating stars. A by-product of this project is the serendipitous collection of multicolour photometry of most interesting compact binaries which show signs of activity, viz. variable periods and strongly variable light curves. This presentation illustrates the project, and concentrates on intriguing species of interacting binaries in NGC 6231.
A New Interpretation of the Low Radial Velocity Determined from the HeII Emission Line in the Galactic Supersoft X-Ray Source RX J0019.8+2156
Authors: Hachisu Izumi , Kato Mariko 
Published: June 2019

We propose a new interpretation for the low radial velocity of He II emission line in the Galactic supersoft X-ray source RX J0019.8+2156 based on a 2-D numerical simulation of dynamical mass transfer in binary systems. A more massive main-sequence (MS) companion of ~ 2.0 M⊙ is derived for a ~ 0.6 M⊙ white dwarf (WD) primary.The Galactic supersoft X-ray source RX J0019.8+2156 (hereafter, RX J0019) with a 12.2 mag optical counterpart was discovered by ROSAT. The source is a binary with the period of 0.66 days and its X-ray luminosity is fairly constant, at least, for 7 yrs. Therefore RX J0019 seems to be a typical luminous supersoft X-ray source (SSS) with steady hydrogen shell-burning on a mass-accreting white dwarf (WD).
Flickering Mapping of the Cataclysmic Variables
Authors: Bortoletto A. , Baptista R. 
Published: June 2019

We report results of simulation to evaluate the ability of the eclipse mapping method to reproduce the spatial distribution of flickering in cataclysmic variables stars.Flickering is a fast intrinsic brightness scintilation occurring on time scales from seconds to minutes with amplitudes of 0.01 - 1 mag. Flickering is observed in all sources believed to be powered by accretion is considered a fundamental signature of accretion. Nevertheless, it is one of the least undestood aspects of the accretion process.
Activity of the New Filament in the Perseid Meteor Stream
Authors: Šimek M. , Pecina P. 
Published: June 2019

AbstractThe activity profile of the new filament in the Perseid meteor stream and its 1986-1994 levels were analyzed from Ondřejov radar observations. The filament was first detected in 1986 at its minimum activity level. Its maximum flux was observed in 1993. A secondary maximum appeared in the period 1988-1989. The cross-section profile of the new cloud shows an activity peak at L⊙ = 138°.87±0°.04 (equinox 1950.0).
STARDUST: Comet and Interstellar Dust Sample Return Mission
Authors: Brownlee D.E. , Burnett D. , Clark B. , Hanner M. S. , Horz F. , Kissel J. , Newburn R. , Sandford S. , Sekanina Z. , Tsou P. , Zolensky M. 
Published: June 2019

AbstractSTARDUST, a Discovery-class mission, will return intact samples of cometary dust and volatiles from comet P/Wild 2, as well as samples of the interstellar dust moving through the solar system. Dust capture utilizes aerogel, a microporous silica that is capable of intact capture of hypervelocity particles. A navigation camera, an in situ dust analyzer, and a dust flux monitor complete the payload. The Wild 2 flyby takes place in January 2004, with Earth return in January 2006.
Mineralogical Changes in IDPS Resulting From Atmospheric Entry Heating
Authors: Keller Lindsay P , Thomas Kathie L. , McKay David S. 
Published: June 2019

AbstractAll extraterrestrial particles are heated during their passage through the Earth's atmosphere. The mineral assemblages that form during entry heating can be used to constrain the maximum temperature attained which, in turn, places limits on their entry velocity Entry velocity can be used to discriminate typical cometary IDPs from asteroidal particles.A common feature of heated IDPs is the presence of magnetite (Mt) rims on the particle surface. These rims range from thin, discontinuous Mt layers on lobes or on small constituent grains within lightly heated IDPs, to thick, continuous, polycrystalline rims that completely surround many strongly heated particles. Petrographic evidence indicates that Mt rims form directly from individual phases in IDPs via oxidation of Fe from the host phases. Our data indicate that the temperature of magnetite formation can range from a minimum of ~600°C (by decarbonation of Fe-bearing carbonates and the breakdown of phyllosilicates) to T > 850°C (decomposition of laihunite). In extreme cases, μm-sized Mt plates armor the surface of partly melted chondritic IDPs. Magnetite rims are more well-developed on hydrated IDPs than on anhydrous particles. The development of magnetite rims correlates with other independent indicators of heating including loss of volatile trace elements and sulfur depletions.
COBE/DIRBE Studies of Scattering By Interplanetary Dust
Authors: Berriman G. B. , Weiland J. L. , Lisse C. M. , Reach W. T. , Hauser M. G. , Kelsall T. 
Published: June 2019

AbstractThe high photometric quality and full-sky coverage in the COBE DIRBE datasets make possible detailed studies of the interplanetary medium. This paper presents a preliminary derivation of the infrared scattering phase function of interplanetary dust. The ultimate purpose of these investigations is to use the DIRBE observations to constrain the composition, size and structure of interplanetary dust grains.
Radial Velocities of Dust Particles in the F-Corona
Authors: Shestakova L.I. , Aimanov A.K. , Aimanova G.K. 
Published: June 2019

AbstractObservations of radial velocities in the F-corona in the elongation range from 3 to 6 solar radii were carried out on July 11, 1991 (Mexico, La Paz) by means of a Fabry-Perot spectrograph. The Fraunhofer lines in the spectral region of H and K Call were used. The average velocities to the West and to the East of the Sun within 30° of the ecliptic plane are +30 km/s and -27 km/s respectively. This confirms the main results of the F-corona radial velocity observations by Shcheglov et al. (1987), Shestakova (1987) on July 31, 1981 about predominance of prograde Keplerian motion of the dust near the ecliptic plane and the effective radius of dust grains (≈0.4μm)
Time Variation of the Solar Dust Cloud
Authors: Kimura H. 
Published: June 2019

AbstractWe have found from line-of-sight integration of scattered light and thermal emission that the appearance of a hump in the F-corona, which was observed in the near-infrared wavelengths by Peterson (1969) and MacQueen (1968), is very sensitive to the change of size distribution of circumsolar dust grains. Namely, the size distribution affects the balance of scattered sunlight and thermal emission. We suggest that a temporal variation in the size distribution of circumsolar dust grains is a potential origin of the temporal variation of the hump structure observed in the F-corona.
Morphology of Cometary Dust Coma and Tail
Authors: Sekanina Z. 
Published: June 2019

AbstractThis paper summarizes some recent progress in our understanding of the morphological diversity of dust comets. This diversity is a product of dust emission from discrete active areas on the nucleus surface and provides information on the comet's rotation state and source function. Advances in computer simulations of large-scale dust coma morphology are described and the diagnostic properties of various dusty features are emphasized. Also addressed are some of the issues of dust tail morphology and particle fragmentation. Finally, constraints on the mass, size, and velocity field of the dust population of comet Shoemaker-Levy 9 are set from the object's morphological observations in 1993-94.
The Mobility of a Hydrogen Atom on an Icy Mantle
Authors: Masuda Koichi 
Published: June 2019

AbstractIt is probable that most molecules in space are formed on the surface of small solid grains in dense molecular clouds. Such grains have generally accumulated icy mantles inside dark clouds. We have investigated the dynamical behavior of a hydrogen atom impinging on the mantle consisting of amorphous water ice based on an MD (Molecular Dynamics) computer simulation to estimate the structure of the resulting grains with the icy mantles. We have found that the hydrogen atoms impinging on the surface of amorphous water ice were easily trapped in a dent of the surface and, consequently they are fixed there firmly. Our results, which neglect tunneling, suggest that the migration of hydrogen atoms over a large region of the surface of icy grains may be less common than is often assumed.
On the crystalline silicate component of comet dust
Authors: Mayo Greenberg J. , Li Aigen , Yamamoto Tetsuo , Kozasa Takashi 
Published: June 2019

AbstractThe effects of preaggregation silicate crystallinity and postaggregation silicate crystallinity on the 11.3μm structure in comet dust emission have been calculated. Of the order of 10 - 20% crystallinity provides the best agreement to date with observation but the fits are not yet fully satisfactory.
The utilization of fish by-products and waste in animal feeding
Authors: Pike I. H. , Tatterson I. N. 
Published: June 2019

Most of the by-products from fish go into the production of fish meal and fish oil, the latter going directly to the human food chain, and therefore do not really come under the heading of industrial by-products and waste per se. Broadly speaking, fish meal made from fish offal is a by-product which otherwise would have been wasted. This paper discusses the quantities involved and the nutritional properties offish meal, and in addition, the contribution to fish meal and fish oil made from species which are not suitable for human consumption (e.g. sandeels) or where the quantities caught exceed the demand for human consumption (e.g. sprats).Any method of utilizing fish by-products for animal feeding should minimize chemical changes in the product to avoid reduction in the nutrients which are present at the time of catching. In some respects chemical changes in fish by-products are brought about in a similar way to those in grass, cut for preservation. The fish material has a high water content, around 75%, and from the time of catching is subject to chemical changes by enzymes in the fish and also by bacterial action. Fish, however, differs from grass in that it contains oil and virtually no carbohydrates. The demersal, or lean fish, for example, cod, haddock, plaice, saithe, etc., contain high levels of oil in the liver which are removed for separate processing, but little in the flesh and in the offal produced. The ‘industrial’ fish caught are mainly pelagic species with high levels of oil in the flesh.