bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Review of Spectrophotometric Studies of Asteroids
Authors: Chapman Clark R. , Johnson Torrence V. , McCord Thomas B. 
Published: July 2016

It has long been realized that studies of the colors of asteroids provide useful clues to their composition. However, only since the development of photoelectric photometry have measurements of asteroid colors proven to be reliable. Recently, with advances in sensors and data systems, it has become possible to measure precisely the spectral reflectivity curves of asteroids from 0.3 to 1.1 µm with higher spectral resolution than that of the UBV system.Until recently, attempts to determine asteroid composition by comparing color indices for asteroids with spectral reflectivities or color indices for meteorites and terrestrial rocks have not been fruitful (Kitamura, 1959; Watson, 1938). It has been noted that the mean color indices for asteroids fall within the range for rocks and meteorites. However, there are far too many minerals for a one-dimensional characterization of asteroid color (color index) to suggest even a compositional class, let alone a specific composition. But when the full spectral reflectivity curve is well defined, for instance in the 24 narrowband interference filters we have been using, the measurements are considerably more diagnostic.
Energy Levels and Spectra of the Li I and Be I Isoelectronic Sequences in the Fourth Row
Authors: Goldsmith S. , Feldman U. , Oren L. , Cohen L. 
Published: July 2016

In the spectra of highly ionized atoms, lines corresponding to different degrees of ionization appear simultaneously on the same region of the photographic plate. Many difficulties are encountered in experimental assignment of the lines to the ionization they correspond to. As a result of this there is a special significance in exact calculations of energy levels. An accurate determination by some theoretical procedure can solve the problem of ionization differentiation.Throughout this work we present theoretical calculations of energy levels of d and p electrons for ions of the fourth row in the isoelectronic sequences of Li i, Be i. We have also calculated the splitting of the various levels.
Measurements of Collisional Rate Coefficients in Laboratory Plasmas
Authors: Kunze H.-J. 
Published: July 2016

AbstractLine radiation emitted by highly ionized atoms embedded in hot laboratory plasmas can be utilized to obtain collisional rate coefficients for excitation and ionization. After a discussion of the principles underlying these measurements, the plasma device mostly used is explained briefly as are the various experimental techniques. All experimental results obtained so far are finally discussed and compared with theoretical calculations where possible.
The Solar Flare Plasma: Observation and Interpretation
Authors: Doschek G. A. 
Published: July 2016

AbstractIn the past several years, X-ray observations of the Sun made from rockets and satellites have demonstrated the existence of high temperature (~20 × 106 – ~100 × 106 K), low density plasmas associated with solar flare phenomena. In the hard X-ray range (λ≲ 1 Å), spectra of the flaring plasma have been obtained using proportional and scintillation counter detectors. It is possible from these data to determine the evolution of the hard X-ray flare spectrum as the burst progresses; and by assuming either a non-thermal or thermal (Maxwellian) electron distribution function, characteristic plasma parameters such as emission measure and temperature (for a thermal interpretation) can be determined. Thermal interpretations of hard X-ray data require temperatures of ~100 × 106 K.Incontrasi, the soft X-ray flare spectrum (1 Å<λ<30Å) exhibits line emission from hydrogenlike and helium-like ions, e.g. Ne, Mg, Al, Si, … Fe, that indicates electron energies more characteristic of temperatures of ~20 × 106 K. Furthermore, line intensity ratios obtained during the course of an event show that the flare plasma can only be described satisfactorily by assuming a source composed of several different temperature regions; and that the emission measures and temperatures of these regions appear to change as the flare evolves. Temperatures are determined from line ratios of hydrogen-like to helium-like ions for a number of different elements, e.g., S, Si, and Mg, and from the slope of the X-ray continuum which is assumed to be due to free-free and free-bound emission. There is no obvious indication in soft X-ray flare spectra of non-thermal processes, although accurate continuum measurements are difficult with the data obtained to date because of higher order diffraction effects due to the use of crystal spectrometers.Soft X-ray flare spectra also show satellite lines of the hydrogen-like and helium-like ions, notably the 1s22s2S-1s2s2p2P transition of the lithium-like ion, and support the contention that in low density plasmas these lines are formed by dielectronic recombination to the helium-like ion. Also, series of allowed transitions of hydrogen-like and helium-like ions are strong, e.g., the Lyman series of S up to Lyman-ε, and ratios of the higher member lines to the Lyman-α line can be compared with theoretical calculations of the relative line strengths obtained by assuming various processes of line formation.This review will discuss the X-ray spectrum of solar flares from ~250 keV to ~0.4 keV, but will be primarily concerned with the soft X-ray spectrum and the interpretation of emission lines and continuum features that lie in this spectral range.
KQ Mon and the Nature of the UX Ursa Majoris Nova-Like Variables
Authors: Sion Edward M. , Guinan Edward F. 
Published: July 2016

ABSTRACTKQ Mon, a new UX UMa type nova-like variable discovered by H.E. Bond, exhibits optical spectra, UBV and high speed photometric characteristics strongly similar to other members of the UX Ursa Majoris subset. However its ultraviolet spectra when compared with other UX UMa stars shed considerable light on the nature of these objects. Its spectrum is dominated by strong broad highly ionized absorption lines including the NV, SiIV and CIV UV resonance doublets. No emission lines or P Cygni type features are evident and the velocity displacements are smaller suggesting the absence of a hot high velocity wind characterizing other UX UMa stars. A physical interpretation of the UV absorption spectra and optical spectra and their observed temporal variations is presented. Based upon (1) high mass accretion rates derived by fitting the observations with theoretical continuum fluxes from steady accretion disk models by R.E. Williams, (2) the presence of outflowing winds with the determination of corresponding mass loss rates and properties of the theoretical wind models by Cassinelli, Olson and Stalio, and (3) new time independent steady state disk structure computations, a model is suggested to explain the observed properties of the UX UMa stars and their lack of major outbursts.
The Peculiar Spectrum of the Extreme Helium Star BD−9°4395
Authors: Jeffery C.S. 
Published: July 2016

AbstractThe spectrum of the extreme helium star BD−9°4395 has already been noted for emission lines of Hel 3889Å and CII 4267Å. Further anomalies in the Hel and CII spectra have been observed, including the identification of additional emission lines, asymmetry in the He I line profiles and variability in all features. It is suggested that these features may be associated with other evidence for non-radial pulsations in BD−9°4395.
Hydrogen-Poor Binary Stars
Authors: Plavec Mirek J. 
Published: July 2016

AbstractHydrogen-poor and helium-rich stars are easy to produce in interacting binaries. Thus they should be found among Population I binaries, in which a large-scale mass transfer has occurred between the components (possibly associated with mass loss from the system). For in such cases, those layers are now on the surface of the “loser” (and, most likely, also on the surface of the “gainer”) that were subject to hydrogen burning and the associated mixing of processed material. Helium overabundance in these objects will be accompanied by an overabundance of nitrogen and underabundance of carbon, as a result of the CNO process. All the Algol-like semidetached binaries should be mild helium stars; so far this has been demonstrated only in β Lyrae, for the He/H ratio is not extreme in such cases. Extreme helium stars require a more complex process, with two stages of mass transfer and/or loss (“case BB”); υ Sagittarii and KS Persei seem to be good examples of this process. The optically invisible components of these two stars seem to have been detected with the IUE. Good model atmospheres do not exist yet, so caution must be exercised in interpreting the UV data.
UV- And Visual Spectroscopy of Nine Extremely Helium Rich Subluminous-O-Stars
Authors: Heber U. , Drilling J.S. , Husfeld D. 
Published: July 2016

AbstractNine helium rich sdO stars are found to show no trace of hydrogen on high resolution visual spectra. Effective temperatures derived from UV fluxes range from 42500 K to 80000 K. A dichotomy with respect to the C/N ratio is found which is reminiscent of the OBN and OBC stars near the main sequence. It is estimated that about 20% of the sdO stars are extremely helium rich. This fraction compares nicely with those of the (helium rich) DB white dwarfs (20%) and the helium rich central stars of planetary nebulae (less than 35%).
Summary
Authors: Hill P.W. 
Published: July 2016

This has been the first international conference devoted to hydrogen-deficient stars and related objects. As Professor Hunger stated in his introduction, one aim of a meeting such as this is to review our achievements and find out what conclusions we can reach about the nature and origin of the objects we study. However, it is even more important that we identity the questions that we must ask and particularly which questions it may be within our means to answer. A newspaper reporter is said to have asked the Chairman of our Local Organizing Committee what we proposed doing to correct this hydrogen deficiency!Our meeting started with Drilling’s review of the galactic distributions and velocity dispersions of the various groups of hydrogen-deficient stars. They cover a wide range from the Population I rapidly rotating intermediate helium stars to the extreme helium stars and cool hydrogen-deficient stars, including the R Coronae Borealis (RCB) variables, which show characteristics of Intermediate Population II. We certainly need to be very clear how each of these classes is defined, particularly as there are a few objects, very definitely hydrogen-deficient, which fail to fit neatly into any of our categories. One star which has been the subject of three contributed papers and mentioned in others has too much hydrogen and too much gravity to be an extreme helium star, too little hydrogen to be an intermediate and too little gravity to be a subdwarf. I refer to BD+13°3224, otherwise known as V652 Her. As many of these stars are discovered to be variable they will be allotted variable star names. To avoid confusion it seems best to mention all known names.
CP-Stars in the Near Infrared: Normal!
Authors: Kroll R. , Schneider H. , Voigt H.H. , Catalano F.A. 
Published: July 2016

Abstract17 CP-stars have been measured in the IR filter bands J,H,K,L and M. No significant differences between CP- and normal main sequence stars can be found. Flux exzesses at 4.8 microns are not confirmed.
Investigations of CP and Normal Stars with Coadded Dominion Astrophysical Observatory Spectrograms
Authors: Hill Graham , Adelman Saul J. 
Published: July 2016

AbstractWe describe the procedures developed at the Dominion Astrophysical Observatory to coadd high dispersion coude spectrograms and thus increase the signal-to-noise ratio in photographic data. These techniques can yield low noise spectra over a considerable wavelength range. Preliminary results of the analyses of such coadditions are shown to demonstrate the power of these procedures.
Intermediate Peculiar Stars: The Bp-Ap Si Stars
Authors: Mégessier C. 
Published: July 2016

AbstractThis paper contains two parts:
1)A review of the most recent results on the silicon peculiar stars. Five topics will be reviewed: parameters of Bp-Ap Si stars — UV spectrum — spectrophotometry — spectrum variations and flux redistribution -magnetic braking.2)The horizontal diffusion of the silicon in the presence of a magnetic field and, as a consequence, the evolution of the silicon abundance repartition in the stellar atmosphere. A first observational test is presented that supports the predicted scenario.
Chemical and Temperature Inhomogeneities on Stellar Surfaces as a Result of an Instability
Authors: Dolginov A.Z. 
Published: July 2016

Observations show that chemical anomalies are distributed inhomogeneously on Ap star surfaces. The most elaborated explanation of the observations is based on the fact that different ions and atoms are affected by radiative forces of different strengths and, hence, have different diffusion velocities. The diffusion across the magnetic field is a factor of (l + νH2/νC2)−1 slower than along the field (νH is the gyrofrequency and νC is the collision frequency of the ions). It leads to the increasing of the heavy ion number density in regions occupied by magnetic traps.However, such an explanation meets a number of difficulties: a) the conditions holds for the most of ion species only in regions where the optical depth is less than 10−2 if the field H exceeds 105 gs. Although little is known on the depth of the region occupied by the chemical anomalies, there are some indirect indications that it is larger than 10−2; b) The observed dipole field has a value 103−104 gs and does not form traps corresponding to the observed chemical spots which have very complicated configurations; c) the magnetic trap is imperfect. The separation process in the field is assumed to be produced by the diffusion which needs a long time. However, ions can escape from the trap together with the surrounding hydrogen plasma because of various plasma instablished which take much shorter time; d) observed space distribution of rare elements and also of Fe, Cr, Ti contradicts the predictions of the magnetic separation hypothesis (cf. V. Khohlova IAU Coll. No. 90, this volume).
The T.60 Operation at Pic du Midi
Authors: Buil Christian , Las Vergnas Olivier 
Published: July 2016

Since Spring 1983, the Pic du Midi and Toulouse Observatory has put the Gentilly 60-cm telescope at the disposal of amateurs. There was an initial experimental trial in 1982, and an amateur Programme Committee was set up in 1983. The “T.60 Association” took over the whole of the operation in 1984. So far, five hundred different amateur astronomers have used the equipment. The prime advantage of the T.60 is its site at the Pic du Midi, 2877 m altitude, one of the best observing sites in the world. By giving new facilities to amateurs, the T.60 offers considerable scientific and educational rewards. Work that has already been carried out includes: determination of H-R diagrams of faint clusters, spectra of planetary nebulae, polarimetric and interferometric studies of nebulae, photoelectric and visual studies of variable stars, research into the chemical composition of faint stars, and observations of mutual phenomena of Jupiter’s satellites.
Obtaining Extraterrestrial Dust by Balloon Probes
Authors: Baufette L. 
Published: July 2016

The “Icare” experiment, involving a balloon at a height of about 30 km was described. The gondola was made of polystyrene, the reasoning being that micrometeorites, by virtue of their velocity, would embed themselves in this to a sufficient degree that they would not be lost during the payload’s recovery and subsequent handling.Electron microscope examination revealed dust particles collected during the flights, and micro-analysis suggests that these are truly of extraterrestrial origin.
New Method of Statistical Analysis of Cometary Light-Curves Applied to P/Halley
Authors: Thebault Serge 
Published: July 2016

Various methods of determining the rotation of P/Halley’s nucleus give 2 periods: 53 hours, and 7.4 days (1). Cometary light-curves are commonly a function of heliocentric magnitude versus the logarithm of heliocentric distance: the result is a set of scattered points. The average light-curve is calculated by the least-squares method. The method proposed here is a reduction of scatter by computation to derive the comet’s specific light variations. The factors causing scatter are: observer experience (physiological and psychological effects), instrumental factors, comet morphology, methods of comparison, and observing conditions. Recently Morris and Edberg (2) have shown that the first three of these were the most important factors. In fact, the prime necessity is to consider visual magnitude estimates as a statistical sample with variability caused by scattering factors. This effect is different for each sample of estimates. Mathematical correction will be applied only after a statistical analysis of the effect of the factors causing error. The method consists of four steps:
1)Computation of heliocentric magnitude (mH) and study of the number of observations for each observer. Observers with less than 10 are omitted (because the least-squares method is not reliable in such a case).2)Correction of instrumental factors and observer effect. Computation by least-squares method is carried out between (mH) versus instrument diameter (D) and exit pupil (P). The diameter and exit-pupil correction is made only if the correlation is significant and not systematic. The correction for observer effect is achieved (for each observer) by least-square computation between mH and logarithm of heliocentric distance. The O–C magnitude is plotted on a graph and a preliminary curve drawn.3)Correction of bias: when a magnitude estimate is made on one night, an estimate the next night will tend to be equal because of psychological effects. It is possible to detect this effect by comparing the number of equal and different magnitude estimates (±0.1 mag) made at time-intervals of 24 hours, and over 24 hours. This comparison is made with the χ2 test. If the test is significant the biased estimates are omitted.4)Other factors (systematic error, photoelectric sequence of comparison stars) are detected by multi-factorial analysis and deleted.
Shape and Frequency of Outbursts of P/Schwassmann-Wachmann 1
Authors: Merlin J.C. , Fayard D. , Gérard E. 
Published: July 2016

AbstractObservations made since the comet’s discovery (1927) were analyzed and reduced to remove observational bias. Comparison was made with possible mechanical effects on the nucleus (tidal forces, impacts). The observations appear to best fit an internal mechanism (exothermic chemical reactions) as proposed by Whipple.
Problems in Publishing a Popular Journal in a Small Country
Authors: Gugnon Pierre , Sauval Jacques 
Published: July 2016

Every journal with a small circulation has the same problems and Ciel et Terre is no exception. The basic cause is the same everywhere: the first thousand copies is far more expensive than the second and subsequent thousands by a factor of 6 to 8 times. This obviously arises from the cost of origination of material. All low-circulations journals have the same financial problems.We have found that it is beneficial to periodically review the following points: the printing process, the format, the frequency, the editorial team, distribution, promotion, subscription fee, etc. In recent years we have found this process to lead to considerable savings.
A Search for Galactic Carbon Stars
Authors: Mabhara Hideo 
Published: July 2016

The carbon star is one of the best probes for the galactic study;
(1)it is intrinsically bright (Mbol = − 2 to − 6) especially in the red and infrared wavelength regions,(2)it has spectral features readily detectable on objective prism plates due to their strong carbon molecular bands,(3)it is an evolved star distributed abundantly (∼1 star per square degree) along the galactic plane.We can detect it in the Galaxy up to several kpc from the sun on objective prism plates of the Schmidt telescope.We have been making survey observations of faint cool carbon stars using the Kiso 105-cm Schmidt telescope. Kodak IN and 103aF plates are respectively taken behind the 4-degree objective prism (700 Åmm−1 at Hα) for the detection and for the spectral classification. V-band plates are utilized to obtain the position and the brightness of the stars detected.The survey areas are distributed along the northern galactic plane. Seven fields in the Cassiopeia region (l = 115° to 133° and eight fields in the Taurus-Auriga-Gemini region (i = 170° to 188°) have been observed and processed up to now (Maehara and Soyano 1987a,b).
Detection of Water Maser Emission from a Carbon Star V778 Cygni
Authors: Nakada Y. , Izumiura H. , Onaka T. , Hashimoto O. , Ukita N. , Deguchi S. , Tanabé T. 
Published: July 2016

Infrared spectra of evolved stars are generally dominated by the radiation from their circumstellar shells. M stars are characterized by the 10 μm emission feature from silicate dust grains, while C stars by the 11 μm SiC band. However, some C stars have been found to show the 10 μm feature indicating the oxygen-rich property of their circumstellar dust (Willems and de Jong 1986, Little-Marenin 1986).In order to investigate the gas phase chemistry of the circumstellar envelopes around these peculiar objects, we have observed radio molecular lines of H2O, SiO, HCN, and CO towards three of them BM Gem (C5, 4J), V778 Cyg (C4, 5J), and EU And (C4, 4).
The White Dwarf Luminosity Function and the Phase Diagram of the Carbon-Oxygen Dense Plasma
Authors: Garcìa-Berro E. , Hernanz M. , Mochkovitch R. , Isern J. 
Published: July 2016

AbstractWe show that the theoretical white dwarf luminosity function depends very much on the assumed phase diagram for the carbon-oxygen dense plasma. Since it is still very uncertain, we compare the two possible extreme cases of complete miscibility and complete separation of carbon and oxygen in solid phase. In the latter case we find that the paucity of low luminosity — log(L/L⊙) ≤ −4.5 — white dwarfs can be explained by the formation of an oxygen core, which releases a large amount of gravitational energy and slows down the cooling rate.
Dredge-up by Sound Wave Emission from a Convective Core
Authors: Kondo Masa-aki 
Published: July 2016

Concerning the scattering of OB stars in the HR diagram (Humphry 1980), the effects of overshooting of convective core (Maeder 1984), mass loss (cf. chiosi and Maeder 1986), and generous stability criterion of semi-convection (Stothers and Chin 1976) have been discussed. Here, we will note the dredge up effect is caused by the sound waves emitted from a convective core.The sound mode of nonradial oscillation, with the spherical harmonics Ylm(θ, ϕ) and the frequency ω, can exist in the propagation zone, where the bottom boundary locates at the position of , and the upper boundary does near the photosphere. Here, Ll is called as the Lamb frequency, and cs is the sound velocity.
Atmospheric Phenomena in ETA Carinae and the Hubble-Sandage Variables
Authors: Viotti R. , Rossi L. , Altamore A. , Rossi C. , Baratta G.B. , Cassatella A. 
Published: July 2016

AbstractFrom the analysis of the galactic counterparts of the HS variables, η Car, AG Car and P Cyg we conclude that their atmospheres are near critical physical conditions so that small changes of the mass outflow could produce a large variation of the atmospheric structure and nova-like explosions at nearly constant Mbol.
Stellar Wind Equations in a New Steady State
Authors: Kato Mariko 
Published: July 2016

AbstractA set of equations of stellar wind in a new steady state in spherically symmetry is presented. This equations are available also for the deep interior of stars, whereas the usual equations can be applied only to the surface region. The new equations have a variable mass flux which becomes zero at the inner boundary of the mass flow. The velocity also reduces zerj), whereas it diverges at r=0 in the usual continuity equation 4∏r2ρ v=constant. In the surface region, the present equations approach the usual equations.