bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Properties of Interplanetary Dust in the Tangential Plane
Authors: Renard J.B. , Levasseur-Regourd A.C. , Dumont R. 
Published: July 2016

AbstractLocal intensity and emissivity, and consequently local polarization degree, temperature and albedo, can be retrieved from optical and thermal observations of zodiacal light. The local polarization degree (normalized at constant solar distance and phase angle) is found to decrease with elevation above the symmetry plane of the zodiacal cloud. The heterogeneity of the cloud, established towards the symmetry pole, is here demonstrated in the tangential plane (almost perpendicular to the ecliptic plane at 1 AU). We present a map of the local polarization degree in this plane.
Asteroidal Dust and the Zodiacal Emission
Authors: Reach William T. 
Published: July 2016

AbstractThe contribution to the brightness of the infrared background by asteroidal dust, distinguished both by lower color temperature and ‘band-pair’ morphology, is determined using IRAS observations. Dust band pairs are associated with at least 7 asteroid families and groups, but very little is detected from the remainder of the asteroid belt, indicating that asteroid families and groups are the source of asteroidal dust.
Spectroscopic Evidence of Organic Molecules Released By the Dust of Halley’s Inner Coma
Authors: Clairemidi J. , Rousselot P. , Moreels G. 
Published: July 2016

AbstractNew spectroscopic arguments supporting the probable presence of organic molecules in the material released by comet Halley are deduced from the data obtained by the Vega three-channel spectrometer. Two excesses of emission on the UV side of the OH and CN bands at 305 and 383 nm are interpreted as being due to “prompt” radiation emitted by electronically excited OH and CN radicals directly produced by the photolysis of water vapor and an organic X-CN molecule. A broad-band emission progressively appears between 342 and 375 nm when the solar scattered continuum has been substracted. This emission increases approximately as the inverse of the projected distance to the nucleus. It is interpreted as a fluorescence emission of organic molecules, possibly condensed polycyclic hydrocarbons. Present observations support the hypothesis of grains coated with organic material and give arguments in favor of a probable interstellar origin for cometary dust.
Ice Particle Emission from Cometary Analogues
Authors: Kohl H. , Grün E. 
Published: July 2016

AbstractDust particles originating from comets are an important constituent of the interplanetary dust regime. In order to study the ejection mechanisms from the cometary nucleus surface simulation experiments in the laboratory have been performed. Samples consisting of water ice, carbon dioxide ice and dust grains have been studied when they are irradiated by artificial sunlight within a cooled vacuum system. It has been shown that particle emission is extremely dependent on the initial composition of the samples. For samples with a distinct amount of non-volatile, mineral particles the formation of a dust mantle and, as a consequence, rapid decrease of particle ejection has been observed.
Polyoxymethylene in Cometary Dust: Laboratory Tests
Authors: Boice D.C. , Naegeli D.W. , Huebner W.F. 
Published: July 2016

AbstractWe have investigated the stability of gas-phase formaldehyde oligomers and its implications for cometary science. Our experiments indicate that when a formaldehyde-methanol solution is vaporized in the mass spectrometer, high molecular mass POM species (45, 61, 75, 91, 105, 121, 135, 151, 165 amu) exist in the gas phase in the temperature range 473 K to 773 K. These laboratory results complement our previous experiments using a formaldehyde-water solution and indicate that formaldehyde oligomers are stable in the gas phase up to at least 6 monomeric units in length. Methanol is important in the end-capping process of the oligomers, leading to increased stability and a richer mass spectrum when compared to the formaldehyde-water solution. The results are consistent with mass spectra obtained by theGiottoPICCA instrument exhibiting alternating 14-16 amu mass peaks.
Spatial Distribution and Color of Dust in Halley’s Inner Coma
Authors: Clairemidi J. , Brandon E. , Rousselot P. , Moreels G. 
Published: July 2016

AbstractComposite images of the intensity of solar radiation scattered by dust in Halley’s coma are constructed by using the three-channel spectra obtained during the approach phase of the Vega 2 spacecraft. They cover a sector centered on the nucleus that has a radius of 40000 km and an angular extent of 50°. A radial plot of dust-scattered intensity shows that it varies as the inverse of impact parameter p where p is smaller than 3200 km or higher than 7000 km. In the intermediate 3200-7000 km distance range, the intensity varies as p−1.52. At longer distances, two jets are present with a contrast comparable to the gas jets which appear in the OH and CN images.The color of dust shows a slight excess of near-UV radiation in a diffuse region between 10000 and 30000 km which appears to be connected with the two jets. In the region called “valley”, between the jets at distances p &gt; 25000 km, the dust-scattered intensity shows an excess of red. The color, expressed as the ratio of intensities at 377,482 and 607 nm is interpreted in terms of Mie theory. It is suggested that the dust particles progressively differentiate. A proportionally more important population of small submicronic grains appears at p &gt; 8000 km. This population seems to correlate with the jets.
Comparison of 3 Micron Features of Trapped H2O and H2O Frost in SiO Condensate with Observed Dust Features
Authors: Wada S. , Sakata A. , Tokunaga A.T. 
Published: July 2016

AbstractWe synthesized a SiO condensate trapping H20 and H20 ice deposited on it. An IR spectrum of the condensate and that of a protostar NGC 7538/IRS 9 were compared. The spectrum of the condensate agreed well with the protostellar spectrum.
Abundances and Chemical Evolution of the Galactic Center
Authors: Audouze Jean 
Published: July 2016

AbstractFrom observations of the galactic center using various techniques radioastronomy, millimeter waves (molecules) – infrared and gamma rays, the interstellar matter of this region* appears to have been strongly processed into stars : the gas density is much lower than in the solar neighbourhood. From CO measurements one knows that there are many molecular clouds such as SgrB2 where stars are forming now. From IR measurements, there are some indication that low mass stars are relatively more numerous in such regions than in the external regions of the galaxy. Finally the heavy element abundances show three important features (i) the possibility of strong enhancements in elements such as N and in a less extent 0 and Ne (the so called abundance gradients), (ii) Some specific enhancements of isotopes such43C,44N and also47O relative to42C,45N and43O (iii) Deuterium seems to have a lower abundance than in other parts of the galaxy such as the solar neighbourhood. Simple models of chemical evolution have been designed to account for such features and are rewiewed here.
Carbon and Nitrogen in Halo Stars
Authors: Sneden Christopher , Peterson Ruth C. 
Published: July 2016

AbstractA new study of carbon and nitrogen abundances has been carried out for a sample of halo dwarf stars. This sample was limited to relatively bright high velocity stars with substantial metal deficiencies (-0.65≥[Fe/H]≥ −2.00). Synthesis of CH molecular bands for nine program stars indicates that [c/Fe] = −0.1±0.2 in halo stars. Preliminary results of the NH synthesis in two stars shows discrepant results: a moderate velocity star has [N/Fe]≲ −1.0 while a very high velocity star has [N/Fe]⋍ +0.0. Implications of these abundances for galactic chemical evolution are discussed.
Inside the Sun: Unsolved Problems
Authors: Schatzman E. 
Published: July 2016

AbstractAs it is impossible to approach all the problems concerning the inside of the Sun, a number of questions will not be taken into consideration during the meeting. In this brief overview of the presently unsolved questions I shall insist on some special aspects of the solar properties: the variations of the solar radius, the generation of the solar wind, some interesting effects due to the presence of a strong gradient of 3He, the history of the rotating Sun. The presence of the planetary system suggests that the Sun might have been a T Tauri star, with an accretion disc and may have started on the mains sequence as a fast rotating star. A sketch is given of the possible consequences.
Solar Opacities Constrained by Solar Neutrinos and Solar Oscillations
Authors: Cox Arthur N. 
Published: July 2016

AbstractThis review discusses the current situation for opacities at the solar center, the solar surface, and for the few million kelvin temperatures that occur below the convection zone. The solar center conditions are important because they are crucial for the neutrino production, which continues to be predicted about 4 times that observed. The main extinction effects there are free-free photon absorption in the electric fields of the hydrogen, helium and the CNO atoms, free electron scattering of photons, and the bound-free and bound-bound absorption of photons by iron atoms with two electrons in the 1s bound level. An assumption that the iron is condensed-out below the convection zone, and the opacity in the central regions is thereby reduced, results in about a 25 percent reduction in the central opacity but only a 5 percent reduction at the base of the convection zone. Furthermore, the p-mode solar oscillations are changed with this assumption, and do not fit the observed ones as well as for standard models. A discussion of the large effective opacity reduction by weakly interacting massive particles (WIMPs or Cosmions) also results in poor agreement with observed p-mode oscillation frequencies. The much larger opacities for the solar surface layers from the Los Alamos Astrophysical Opacity Library instead of the widely used Cox and Tabor values show small improvements in oscillation frequency predictions, but the largest effect is in the discussion of p-mode stability. Solar oscillation frequencies can serve as an opacity experiment for the temperatures and densities, respectively, of a few million kelvin and between 0.1 and 10g/cm3. Current oscillation frequency calculations indicate that possibly the Opacity Library values need an increase of typically 15 percent just at the bottom of the convection zone at 3×106K. Opacities have uncertainties at the photosphere and deeper than the convection zone ranging from 10 to 25 percent. The equation of state that supplies data for the opacity calculations fortunately has pressure uncertainties of only about 1 percent, but opacity uncertainties will always be much larger. A discussion is given about opacity experiments that the stars provide. Opacities in the envelopes of the Hyades G stars, the Cepheids,δScuti variables, and theβCephei variables indicate that significantly larger opacities, possibly caused by iron lines, seem to be required.
Using Helioseismic Data to Probe the Hydrogen Abundance in the Solar Core
Authors: Gough D. O. , Kosovichev A. G. 
Published: July 2016

AbstractA procedure for inverting helioseismic data to determine the hydrogen abundance in the radiative interior of the sun is briefly described. Using Backus-Gilbert optimal averaging, the variation of sound speed, density and hydrogen abundance in the energy-generating core is estimated from low-degree p-mode frequencies. The result provides some evidence for there having been some redistribution of material during the sun’s main-sequence evolution. The inversion also suggests that the evolutionary age of the sun is perhaps some 10 per cent greater than the generally accepted value, and that the solar neutrino flux, based on standard nuclear and particle physics, is about 75 per cent of the standard-model value.
Surface Abundances of Light Elements as Diagnostics of Transport Processes in the Sun and Solar-type stars
Authors: Baglin A. , Lebreton Y. 
Published: July 2016

AbstractObservations of the surface abundances of lithium, beryllium and helium-3 in the Sun and in solar-type stars of different ages should be interpreted in a coherent way. The abundance of lithium at the surface of a star decreases slowly with age; for stars of the same age it decreases with mass and a dependence on the rotation velocity is suggested. The solar surface lithium is depleted by a factor of 100 relative to the cosmic abundance while an He-3 enrichment of 15% at the solar surface during evolution is suggested.Observations favour the hypothesis of a slow transport process at work between the outer convective zone and the radiative interior of these stars. Orders of magnitude of the transport coefficient as well as its dependence upon the physical parameters can be inferred from surface abundances of light elements, but at the moment we are far from producing a completely consistent modelization.
Where is Nova 1437? - Surprises in the Space Density of Cataclysmic Variables
Authors: Shara M. M. , Potter M. , Moffat A.F.J. , Bode M. , Stephenson F.R. 
Published: July 2016

AbstractA U-B search to 21st magnitude in a 1°×1° region centered on the best position for the Korean nova of 1437 has revealed no unique candidate. Instead, we find 7 faint UV-bright stars with CV-like emission lines. The implied space density is two orders of magnitude higher than the classical space density for CV’s.
V 1500 Cyg: Slow Variability in Post-nova Stage
Authors: Pavlenko E. 
Published: July 2016

Regular photometric observations of V1500 Gyg (Nova Cygni 1975) have been carried out at the Crimean Astrophysical Observatory of the USSR Academy of Sciences from 1975 till now. The 0.5 m telescope equipped with a TV system is used to estimate the star brightness in V.The decline of the mean brightness is presented in Figure 1. The solid lines (1) and (2) show the changes of the V brightness according to Patterson (1979) and Arkhipova and Zaitseva (1978), respectively. The dotted line is drawn according to our data (Pavlenko 1988). The arrows indicate the amplitudes of the light and colour variations.
Maximum Magnitude Vs. Rate of Decline for Novae of the LMC
Authors: Capaccioli M. , Della Valle M. , D’Onofrio M. , Rosino L. 
Published: July 2016

AbstractWe derive the distance modulus of the Large Magellanic Cloud (LMC) by applying the new calibrated relationship between maximum magnitude and rate of decline (MMRD). The result, , is in close agreement with the most recent determinations based on RR Lyrae and Cepheids. We also discuss the properties of the MMRD of M31 and of the LMC.
Physical Properties and Abundances of Novae in the Nebular Phase
Authors: Snijders M.A.J. 
Published: July 2016

AbstractWe discuss the derivation and behaviour of temperatures and densities of nova ejecta during the nebular stage. A systematic comparison is made between fairly complete sets of abundances for 3 C/O and 2 Neon novae. The abundances in the ejecta might influence the formation and composition of circumstellar dust in novae.
Soft X-Ray Emission from Classical Novae in Outburst
Authors: Starrfield Sumner , Truran James W. , Sparks Warren M. , Krautter Joachim , MacDonald James 
Published: July 2016

AbstractTheoretical modeling of novae in outburst predicts that they should be active emitters of radiation at soft X-ray wavelengths twice during their outburst. The first time occurs very early in the outburst when only a very sensitive all sky survey will be able to detect them. This period lasts only a few hours for the very fastest novae. They again become bright in X-rays late in the outburst when the remnant object becomes very hot and is still luminous. Both simulations and observations show that novae can remain very hot for months to years. It is important to observe them at these late times because a measurement both of the flux and temperature can provide information about the mass of the white dwarf, the turn-off time scale, and the energy budget of the outburst.
The Origin and Evolution of Novae
Authors: Tutukov A.V. , Yungelson L.R. 
Published: July 2016

AbstractThe cataclysmic binaries are products of the nonconservative evolution of close binaries with large initial mass ratios of components. The accretors in cataclysmic binaries can be helium or carbon-oxygen or oxygen-neon-magnesium white dwarfs. Their annual birthrates are ~0.005, ~0.005, and ~0.00005 respectively. In one-zone approximation of a thin accreting shell we estimate the critical masses of hydrogen and helium shells and recurrence time scales of thermonuclear runaways.
Effective Growth Rate of White Dwarf Mass in Nova Outbursts
Authors: Kato Mariko , Hachisu Izumi 
Published: July 2016

AbstractWe have obtained the effective growth rate of white dwarf masses which are suffering mass loss during both hydrogen and helium nova outbursts. If the mass transfer rate from the companion is smaller than 10−7 M⊙/yr, the net growth rate is reduced to less than one tenth of the mass transfer rate from the companion star. It is suggested that the white dwarf mass is hard to grow to the Chandrasekhar mass unless its initial mass is very close to the Chandrasekhar limit.
The White Dwarf Mass and Orbital Period Distributions in Zero-Age Cataclysmic Variables
Authors: Politano M. , Webbink R.F. 
Published: July 2016

A zero-age cataclysmic variable (ZACV) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACVs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years. These results differ from previous work (Politano and Webbink 1988) in that an improved criterion for stability against rapid mass transfer by the secondary to the white dwarf has been used. A brief outline of the method and key assumptions made in this calculation is given in Politano and Webbink (1988).The white dwarf mass distribution of ZACVs (shown in Figure 1) contains two components: systems with helium white dwarfs and systems with C-0 white dwarfs. Systems with helium white dwarfs comprise slightly greater than 50% of all ZACVs. The helium white dwarfs have masses which range from 0.27 to 0.46 solar mass. The C-0 white dwarfs have masses which range from 0.54 solar mass up to the Chandrasekhar mass. (Note: systems with O-Ne-Mg white dwarfs are not distinguished from systems with C-0 white dwarfs in this calculation. Presumably, these O-Ne-Mg systems comprise the upper end of the white dwarf mass distribution.)
IR Observations of the Symbiotic Nova HM Sagittae
Authors: Taranova O.G. , Yudin B.F. 
Published: July 2016

The infrared photometry of the symbiotic nova HM Sge, with a Mira variable as a cool component, shows that since 1983 its mean IR brightness began to decrease from the previous post-outburst level (Figure 1). In 1988 the mean J magnitude was already about 1 mag fainter than it had been until 1983.An analysis of the photometric observations shows that the decrease in the mean IR light level of HM Sge may be understood in the framework of the commonly accepted model of this binary stellar system (Taranova and Yudin 1983), if we suggest that the Mira variable and the inner parts of its circumstellar envelope (RMira envolope~ 3×l014 cm; τdust ≲ 1 at 1.25 µm until 1983) were gradually obscured by the dust originated between them and the observer.
The nova type outburst of the symbiotic star AS 296
Authors: Munari Ulisse 
Published: July 2016

AbstractThe photometric and spectroscopic evolutions, displayed by AS 296 since the June 1988 outburst ([1]), are presented and discussed. The main features of the model outlined by [2], [3] and [4], are confirmed and further developped. An orbital period of about 3 years is inferred from Hα modulation (see [5]).The outburst originated from a TNR event in the accreted envelope of a WD. The IUE and optical spectroscopic evolution agrees with the expected scenario for degenerate conditions in the accreted material, while the high quiescence luminosity of the WD would indicate nondegenerate conditions.The late type giant passed unchanged the outburst. Also the region of Hα formation was not touched by the eruption.After one year the system has not yet reached the quiescence again. The photometric evolution displayed by AS 296 up to June 15, 1989 is presented in Fig.1.In Tab.1, the main features exhibited by symbiotic stars that have experienced a TNR event are summarized. The first 8 objects in the table are usually collectively called "symbiotic novae". They distinguish themselves for the very long outburst duration. At present, AS 296 appears to be a borderline case of such class, and a firm understanding needs to wait for the end of current active phase.
Observational Evidence on the Interaction of Orion Population Stars and the Interstellar Medium
Authors: Grasdalen G. 
Published: July 2016

The Orion population stars are those stars which have only recently formed. It is generally accepted that these stars arose as condensations in the interstellar medium. It follows that they should show strong interactions with that material. In only one case, the nebula near T Tauri (Schwartz 1974) do we have any direct evidence for the interaction between these stars and the interstellar medium. Presumably this is because the typical interactions take place on much larger or much shorter distance scales. The long range interaction of young stars with their environment is discussed in Section II.It is also generally agreed that Orion population stars are still enshrouded in circumstellar material. There are important questions that have yet to be answered about that material before we can begin to discuss the details of any interaction between these stars and their surroundings. These difficulties are discussed in Section III.Finally, I have chosen four topics to discuss in somewhat more detail. My aim has been either to urge caution in accepting current interpretations or to put caution aside and suggest new possibilities.
Simultaneous Spectroscopic and Photometric Observations of the YY Orionis Star S CrA
Authors: Mundt R. , Wolf B. 
Published: July 2016

AbstractThe YY Orionis stars are a subclass of the T Tauri stars which show in their spectra evidence for infailing envelopes. They are interpreted as protostars in the final stages of their hydrodynamical evolution (Walker 1972, Appenzeller and Wolf 1977, Wolf et al. 1977).To get more information about the behaviour of these highly variable stars simultaneous spectroscopic and photoelectric (UBV) observations have been carried out in July 1977 at the ESO observatory at La Silla. Such observations of YY Orionis stars have never been done before.The most frequently observed star during our run was the bright YY Orionis star S CrA. The observational material is still under evaluation and therefore only some preliminary results are presented here. A more extended description and discussion of the observations will be published elsewhere (Mundt and Wolf, 1977).