bluuebunny/crossref_metadata_2025 huggingface dataset:
The Relation of Algols and W Serpentis Stars
Authors: Wilson R. E.
Published: July 2016

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

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

We computed the evolution through case A mass transfer for 8 systems with mass of the primary equal to 3 and 5 Mo, mass ratios 0.7 and 0.9, and different periods. To this we added similar results from Packet (1988) for Mi=9 Mo, qi=0.6, Pi=1.62 d.

During the mass transfer two competing mechanisms in the gainer decide on the evolution of the system: the rejuvenation of this star as the increasing convective core mixes fresh hydrogen into the inner regions, and the acceleration of nuclear burning, responding to the increasing mass.

In all the cases the net result is a faster decrease of the central hydrogen content compared to the mass losing star. The secondary fills its own critical Roche lobe and reversed mass transfer starts.

From our results and those of Nakamura and Nakamura (1984), we find that reversed mass transfer occurs after core hydrogen burning of the secondary (case A1B2) approximately for periods larger than 1 d (Mli=3 Mo) to 2 d (Mli=l3.4 Mo). For smaller periods this happens before the gainer ends its core hydrogen burning (case A1A2).
Absolute Dimensions of Algol Binary Systems
Authors: Garcia J.M. , Gimenez A.
Published: July 2016

In order to check the evolutionary status and theoretical models of eclipsing binaries of Algol type, a reliable determination of their absolute dimensions is needed. In this communication, we compare the most commonly used methods to derive absolute parametors in single-lined aclipsing binaries. Let us first assume that the mass function, f(m), is known from the analysis of the radial velocity curve while the relative radii and orbital inclination are derived from the light curve. The determination of absolute parameters is then equivalent to the obtention of the mass ratio, q = m2/m1. The following methods are available to estimate q from observed parameters — over-all errors being estimated for observational uncertainties of the order of 5 % in relative radii and temperatures and 15 % in f(m) —:

1.

qs: It is assumed that the primary component follows the mass-luminosity relation for main-sequence stars. This procedure provides qs with an uncertainty of about 10 %.

2.

qsD: It is assumed that the secondary component fills its Roche lobe. Errors of at least 15 to 20 % are expected from this procedure mainly due to its high sensitivity to small variations in the observed value of r2, particularly if r2 > 0.2.

Both methods can be used together when f(m) is doubtful, or completely unknown, but errors can not be expected to be better than in case 2.

3.

qn: It is assumed that the primary component rotates synchronously in a circular orbit. This assumption is difficult to adopt due to the expected transfer of angular momentum through mass transfer and the value of qn is estimated with about 20 to 30 % error.

4.

qED: It is assumed that the primary component, is well reproduced by standard evolutionary models within the main sequence. Adopting a grid of models for a given chemical composition, an iterative procedure in the log Ti,.–log g plane permits the determination of m1 and thus q. This method is equivalent to (1) but avoids errors due to evolution from the ZAMS to the TAMS, not taken into account in the previous method, and allows to reach a higher accuracy, around 5 %, except for those primary stars located around the TAMS, where the determination of mi is not unique.
Absolute Dimensions and Evolutionary State of RS Vulpeculae
Authors: Holmgren D.
Published: July 2016

RS Vul (HD 180939, VMax =7.0, B5V+G1III) is a semi-detached eclipsing binary with a period of 4.4776635 days. High signal-to-noise (S/N ≃ 100) spectra have been obtained with the 1.2m telescope and coudé Reticon spectrograph of the Dominion Astrophysical Observatory. The FeI 4045Å, 4227Å (blend of CaI, FeI and TiII) lines and G-band (4300Å) of the secondary are weakly visible on the spectra. Radial velocities measured from the spectra using a digital cross-correlation technique (Hill, 1982) have been used to compute a new spectroscopic orbit for the system. The primary and secondary semi-amplitudes are 54.0 ± 1.0 kms−1 and 204 ± 2 kms−1 respectively, assuming a circular orbit. The primary and secondary orbits are “decoupled” in the sense that velocities for the components can be measured separately on the same spectrum by using B5V and GOV template spectra. The secondary semi-amplitude is 17% larger than that found by Popper (1982), but the mass ratio (3.7) is identical to that found by Hutchings and Hill (1971).
Radial Velocity Variations of the Be Shell Star V923 AQL /HD 183556/ in the Past Sixty Years
Authors: Koubsky P. , Gulliver A.F. , Harmanec P. , Ballereau D. , Chauville J. , Gráf T. , Horn J. , Iliev L. , Lyons R.
Published: July 2016

The analysis of 149 radial velocities of V923 Aql from 1927 to 1987 revealed that the observed RV variations arise from a superpositon of cyclic long-term velocity variations of variable amplitude and cycle length / 20≦2K≦65 km.s-1, 1800d≦P≦2400d/ and an orbital motion with a period of 214.75 days and an amplitude 2K=12.4 km.s-1. The binary system consists of a B5-7 e primary and low-mass /about 0.5 M⊙/ secondary separated some 250 R⊙. Both, the long orbital period and low mass ratio are typical of /interacting/ binaries containing a Be star. The observed cycle length of the long-term changes are very similar to those observed for ɽTau, the only Be binary with the long-term variations known to date. V923 Aql thus becomes the second representative of binary Be stars, for which it is conceivable to interpret the long-term variations by an elongated envelope, revolving due to the attractive force of the secondary, and'formed by the process of mass transfer from the secondary to primary, as predicted by the binary model of the Be phenomenon.
Binary Statistics and Star Formation
Authors: Zinnecker Hans
Published: July 2016

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

A catalogue of galactic novae and an atlas of finding charts are under preparation and will be published in 1984. The status of the project is described.
A Comparison Between Binary Star Light Curves and Those of Possible Binary Asteroids
Authors: Schober H. J.
Published: July 2016

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

One of the prime astrophysical interests of the Observatorium Bosscha is, and has always been, double star research: visual double star research with the double-60 cm Zeiss telescope (dedicated in 1928), and theoretical research of evolved massive spectroscopic binaries (since 1972). For one thing, this is the very reason that this IAU Colloquium No. 80, celebrating the 60th anniversary of the Observatorium Bosscha in Lembang, is devoted to binary astrophysics.

Up to now, visual, photographic, and photometric tools have been used for binary research at the Observatorium Bosscha. An important, essential additional tool for binary research is spectrographic equipment, in order to measure radial velocities of binary components.
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.
Motion of Small Particles in the Solar System
Authors: Alfvén Hannes
Published: July 2016

Unlike planets and satellites, smaller bodies in the solar system, like asteroids, comets, and meteoroids, are affected by nongravitational forces due to collisions, viscosity, and in some cases electromagnetic forces. The way such forces change the orbits of the bodies seems not to have been analyzed until recently. For example, it is generally believed that collisions between asteroids will make their orbits spread over an increasing volume of space and that collisions inside meteor streams will make their cross sections increase. At least under certain conditions the reverse is true, as shown by the papers of Baxter and Trulsen at this symposium. Furthermore, besides the usual picture of meteoroids being emitted by comets, we should also discuss the reverse process; viz, comet formation by bunching in a meteor stream.
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

Line 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

In 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

KQ 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.
Column Accretion on to White Dwarfs
Authors: King A. R.
Published: July 2016

The problem of column accretion on to white dwarfs in the AM Her and DQ Her systems is reviewed. Particular attention is paid to recent progress in explaining the large soft X-ray - EUV fluxes observed in these systems in terms of nonlocal electron energy transport into the white dwarf photosphere.
Astronomy in Israel: From Og’s Circle to the Wise Observatory
Authors: Ne’eman Yuval
Published: July 2016

Colloquium IAU 72 is the first IAU-sponsored activity in this country, and it therefore seemed appropriate to include a paper on Astronomy in Israel. With the highly singular history of this nation, the scene will move from Eretz-Israel to Babylon (present day Iraq) and to Europe before returning to this area.
Photometric Properties of the Extreme Helium Stars
Authors: Landolt Arlo U.
Published: July 2016

The purpose of this paper is to review the photometric histories of the extreme helium stars.
The Peculiar Spectrum of the Extreme Helium Star BD−9°4395
Authors: Jeffery C.S.
Published: July 2016

The 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

Hydrogen-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

Nine 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.
Study of Inhomogeneities on the Surface of Magnetic CP Stars
Authors: Khokhlova V.L.
Published: July 2016

The formulation and solution of the inverse problem to determine local Stokes parameters on the surface of a star, in particular magnetic chemically peculiar star, and hence to determine surface abundance distribution and magnetic field geometry is reviewed.
Rotation, Variability and Age of Ap Stars
Authors: North P.
Published: July 2016

Photometrically determined gravities for field and cluster Ap stars, together with published periods, show that conservation of angular momentum alone is responsible for the observed increase of the periods with age. New photometric periods of a few cluster stars are presented which independently confirm this result. No outstanding change with age of the amplitude of lightcurves is noted.
CP-Stars in the Near Infrared: Normal!
Authors: Kroll R. , Schneider H. , Voigt H.H. , Catalano F.A.
Published: July 2016

17 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

We 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

This 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

Observations 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.
Photometric Analysis of the Solar Corona on 1984 November 22/23
Authors: Caron Roland , Nitscheim Christian , Sarrazin Michel
Published: July 2016

The total solar eclipse of 1984 November 22/23 was observed from a French naval vessel off Noumea (New Caledonia) in the Coral Sea. The observations were made by a team from the S.A.F., led by Serge Koutchmy and Christian Nitschelm of the Institut d’Astrophysique de Paris. The duration of the eclipse was considerably longer off New Caledonia (1 m 39 s) than in Papua-New-Guinea (55 s). However, the observational site – on board a ship well out to sea – greatly restricted the use of long-focal-length instruments that are normally employed. The equipment used to photograph this eclipse therefore was chosen with motion (pitching, rolling, etc.) of the support in mind. Short focal lengths were preferred, although one refractor with a focal length of 1.5 m was used as a trial.
Meteor Studies
Authors: Lindblad B.A.
Published: July 2016

Historically meteor astronomy is one area where amateurs have always been able to make significant contributions. In fact, in the 19th century, it was amateur naked eye and telescopic observations which laid down much of the foundations of meteor astronomy. References to this work can be found in any textbook on meteors. The 19th century observers concentrated on counting meteors, estimating magnitudes and plotting the meteor paths on star maps. Their main interest was to determine hourly rates and shower radiants. An important milestone was Denning’s radiant catalogue (Denning 1882), which included 4367 shower radiants. Although it is now believed that many of these radiants are spurious, the catalogue is still a useful reference. Unfortunately Denning and other 19th century observers often combined sporadic meteors observed on different nights into a minor stream radiant. This habit of “radiant hunting” is even today quite popular among some amateur observers. However, in all fairness it should be emphasized that most of the 20th century amateur meteor observers applied very strict criteria to their radiant determinations. Names such as J.M. Prentice in Great Britain, R.A. McIntosh in New Zealand and R. Rigollet in France may be mentioned.
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.
The Bruno-H.-Bürgel Observatory
Authors: Busch Helmut
Published: July 2016

The observatory is both a school and public observatory. Lectures are arranged for pupils at various levels as well as courses for teachers. Since 1959 astronomy has been a compulsory subject in schools in the D.D.R. (one of only four countries in the world in which this is the case). The observatory also participates in scientific work, particularly in the field of variable stars, where it has always had very close links with Sonneberg Observatory.
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

We 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

From 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

A 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.
Distance Determination of Mass Losing Carbon Stars from CO and HCN Radio Observations
Authors: Unno Wasaburo , Tsuji Takashi , Koyama Kou-ichi , Izumiura Hideyuki , Ukita Nobuharu , Kaifu Norio
Published: July 2016

A method of distance determination of evolved carbon stars is proposed and applied to six stars for which the terminal velocity of expansion and the angular size are obtained from the CO and HCN radio observations made at the Nobeyama Radio Observatory. The method assumes the radiation driven wind in spherical geometry. Within those small samples, however, two types of mass losing stars that are systematically different in the antenna temperature ratio TA (CO)/TA(HCN) ≷1, in the velocity ratio υ(CO)/υ(HCN)≶1, and in the angular size ratio θ(CO)/θ(HCN)≷1 seem to be present, suggesting nonspherical geometry of the outflow.
Photospheres of Mira Variables
Authors: Bessell M.S. , Brett J.M. , Scholz M. , Takeda Y. , Wehrse R. , Wood P.R.
Published: July 2016

Mira variables form an important subgroup of the red giant stars which are typical representatives of stars showing burnt material at their surfaces. Since the photospheres of Miras are not in hydrostatic equilibrium but are characterized by spherically very extended density stratifications, their properties and emitted spectra differ substantially from those of non-Miras, and any attempts to analyse Mira spectra by means of conventional techniques must fail. Non-hydrostatic models are needed for analysis work.

We computed a small set of exploratory M type (solar abundances) Mira model photospheres whose density distributions were taken from an improved modification of a pulsation model proposed by wood (1979). Besides the fundamental model parameters, i.e. mass, luminosity and radius (or effective temperature), the parameters of the density stratification (e.g. the heights of the density discontinuities at the shock front positions, or the effective gravity acting between two successive shock fronts) must be treated as free parameters within certain limits, owing to insufficient knowledge of the velocity stratification entering the pulsation model. Typical density and temperature stratifications are shown in Fig. 1 of Scholz (1987). Both CO lines, measuring the outflow and infall velocities of matter between the shock fronts, and selected moleculer band features (colors) were found to react sensitively to adjustments of the model parameters. As an example, Fig.1 shows the differences between CO line profiles computed from the near-maximum model of Fig.1 of scholz (1987) (Fig.1a) and those computed from a model in which the effective gravity between the shock fronts was increased by a factor of 1.5 (Fig. 1b). The same velocity stratification was adopted in of monochromatic radii proves to be a powerful tool of diagnostics of Mira photospheres (Scholz and Takeda 1987; Bessell et al. 1987).
W Ursae Majoris Star Models: Observational Constraints
Authors: Linnell Albert P.
Published: July 2016

W Ursae Majoris stars can be understood as contact binary stars with a common envelope (Lucy 1968). They subdivide into two types: The A-type are earlier inspectral class than about F5, are believed to have radiative envelopes, and associate primary (deeper) eclipse minimum with transit eclipse. The W-type have spectral classes later than F5, are believed to have convectlve envelopes, and associate primary minimum with occultation eclipse. Controversy has surrounded the explanation of W-type light curves.

Four distinct models have been introduced to describe the envelopes or photospheres of W UMa stars. (1) The Rucinski hot secondary model directly explains W-type light curves on a postulational basis. Since 70%-90% of the emitted radiation from the secondary (less massive) component is believed to reach the secondary via circulation currents from the primary, there is an apparent thermodynamic mystery why the secondary should be hotter. (2) The Lucy Thermal Relaxation Oscillation (TRO) model argues that the secondary component is perpetually out of thermal equilibrium and that the components are in contact only during part of a given TRO cycle. During contact the photosphere is supposed to be barotropic. In this case primary minimum always associates with transit eclipse, in disagreement with observation for W-type systems. (3) The Shu et al. thermal discontinuity (DSC) model also argues for a barotropic photosphere but differs from Lucy on the gravity brightening exponent. The changes are insufficient to produce W-type light curves, (4) Webbink (1977), and, separately, Nariai (1976), argue for a baroclinic envelope. If the baroclinicity extends to the photosphere there is a possibility that W-type l i g h t curves could be explained. In particular, the Webbink scenario produces a hot secondary.
Carbon Abundance in Mass-Exchanging Binaries
Authors: Cugier H. , De Greve J.P.
Published: July 2016

The evolution of the carbon abundance at the surface of both components of a mass-exchanging (Algol-type) binary is examined (fig. 1). Distinction is made between case B and case AB (fig. 2) of mass transfer, in view of the different timescales involved. In the mass accreting component thermohaline mixing is adopted when matter with decreasing hydrogen abundance is deposited on the surface.

It is shown that at the surface of the loser a very low C-abundance is present, while at the surface of the gainer different regimes occur. On the average the expected C-abundance on the gainer is clearly lower than the observed solar value, but far above the value at the surface of the loser. The variation in time during the mass-exchange process is compared to the values, derived from observation of several Algol-type systems.
Spectral Peculiarities in Nova Vulpeculae 1984 N° 2
Authors: Andrillat Yvette , Houziaux Léo
Published: July 2016

This slow nova has been observed spectroscopically at Observatoire de Haute-Provence in two wavelengths regions: 330–460 nm (plate factors: 4 and 8 nm), and 750–1100 nm (plate factors: 23 and 26 nm/mm).

Time coverage includes the following stages: close to maximum of light, early nebular phase and advanced nebular stage.

Spectra are similar to those of classical novae: strong continuum, wide emission bands with double structure, flanked by a moderate strength absorption component at −1400 km/s.The following ions are identified: H I, O I, C I, N I, Mg I and II, Ca I and II, Fe II, Ti II, Si II and Sr II.
Observation of a Neutrino Burst from the Supernova SN1987a: The KAMIOKANDE-II Collaboration
Authors: Totsuka Yoji
Published: July 2016

A neutrino burst was observed in the KAMIOKANDE-II detector on 23 February, 7:35:35 UT ( ±1 minute) during a time interval of 13 seconds. The signal consisted of 11 electron events of energy 7.5 to 36 MeV, of which the first 2 point back to the Large Magellanic Cloud (LMC) with angles 18° ± 18 ° and 15° ± 27°.

A new analysis of the special low threshold trigger counts strongly indicates that KAMIOKANDE did not observe any signals at 2:52:36 which is the time claimed by the Mont Blanc group.