bluuebunny/crossref_metadata_2025 huggingface dataset:
Does the Cataclysmic Binary Z Cha Contain a Black Dwarf Secondary?
Authors: Faulkner John , Ritter Hans
Published: July 2016

It is shown that the assumption of a black dwarf secondary in Z Cha leads to a number of contradictions with well established theoretical and observational facts. In particular the model predicts the radial velocity K1 to be much smaller than is observed, the radius of the accretion disk to be smaller than is physically possible and a white dwarf mass which is inconsistent with the white dwarf's radius derived from eclipse analysis. Using the same arguments as for Z Cha it is also possible to exclude a black dwarf secondary in the similar systems OY Car and HT Cas.
Microwave emission from Saturn’s rings
Authors: Muhleman D.O. , Berge G.L.
Published: July 2016

Passive radio measurements of Saturn’s Rings are reviewed and new interferometric measurements at λ = 2.7 mm are presented. The brightness temperatures of the A plus B rings at a ring angle of B ⋍ 10° were found to be 17 K and 38 K in two separate experiments, the latter being the more reliable. These results are interpreted in terms of ring particle emission and scattering of the planet’s disk emission by the rings.
Saturn’s E-ring in the red spectral region
Authors: Feibelman W.A.
Published: July 2016

Observations of the 1966 edge-on presentation of Saturn’s E-ring in the red spectral region are presented. Techniques to suppress the glare from the planet are briefly described. The E-ring profile did not exhibit a maximum near the orbit of Enceladus in 1966. Some historical comments concerning the E-ring are included to illustrate that important planetary work can be done by ground-based observations.
Infrared observations of the Uranian rings
Authors: Nicholson P.D. , Jones T.J. , Matthews K.
Published: July 2016

We present maps of the Uranian rings at an effective wavelength of 2.2 µm, and spectrophotometric observations covering the ranges 2.0 – 2.4 µm and 2.9 – 3.9 µm. The maps, constructed from data obtained in May 1978 and July 1979, reveal a 2:1 azimuthal brightness variation whose amplitude and phase are consistent with the known width variation and apsidal precession of the eccentric e ring. A detailed comparison of the maps with models based on stellar occultation data leads to an upper limit of ~0.01 on the normal optical depth of any broad (5000 km wide), diffuse component of the ring system. An unexplained feature of the 1978 map is a significant east-west asymmetry, corresponding to a brightening of the near side of the rings relative to the far side.
The C ring of Saturn: A high resolution view of some of its structure
Authors: Lane Arthur L. , Graps Amara L. , Simmons Karen E.
Published: July 2016

The high resolution examination of selected features in Saturn's C-Ring has demonstrated that they are far more complex than previously considered. This brief paper illustrates several classes of the phenomena observed by the Voyager Photopolarimeter star occultation experiment.
Statistical study of Saturnian electrostatic discharges observed by the Voyager planetary radio astronomy experiment
Authors: Zarka P. , Pedersen B.M.
Published: July 2016

During the two Voyager-Saturn missions, the Planetary Radio Astronomy experiment observed sporadic broadband (20 KHz to at least 40 MHz) emissions during a few days around the closest approaches.

These emissions are interpreted to arise from short-lived electrostatic discharges in the vicinity of Saturn. Their characteristics have been studied for the experiment's high band (>1.2 MHz).

A difference between the periodicity of these Saturn electrostatic discharges (SED) is found, when comparing Voyager 1 and 2 observations.
Viscosity in Saturn's rings
Authors: Lissauer Jack J. , Shu Frank H. , Cuzzi Jeffrey N.
Published: July 2016

We discuss the technique of estimating the viscosity in Saturn’s rings from the damping rate of waves observed to be propagating within the rings. Previously published attempts rely on spiral density waves as a diagnostic, and the wavetrains used in the analyses suffered significant complications that compromised the interpretations. We present a new method that considers the damping of spiral bending waves, a diagnostic which is largely free of,major complications. We deduce a kinematic viscosity of 260 (+150, -100) cm2/s for the middle of the A ring where bending waves have been excited by the 5:3 vertical resonance with Mimas. This value implies upper limits on the particle velocity dispersion and local ring thickness of 0.4 cm/s and 30 m, respectively.
Physical and geological nature of Saturn's larger ring particles
Authors: Chapman Clark R. , Greenberg Richard , Weidenschilling Stuart , Davis Donald R.
Published: July 2016

The evolution and behavior of Saturn’s rings may be influenced by relatively large ring particles. We describe how an important mass fraction of the rings may reside in particles with dimensions of tens of meters to kilometers, which are too few to be seen by radio occultation and too small to be detected in Voyager pictures. We consider the possible physical and geological structure of such bodies and how they influence interactions among ring particles in general.
Effects of shepherd conjunctions on Saturn's F ring
Authors: Showalter M.R.
Published: July 2016

Synnott (1982a) has reported that the F-ring braids are often found near the ring segment which was between the shepherds at their last conjunction. We study the possible perturbing effects of such conjunctions on the ring , and find that they are much too small to directly account for the braids.
The gravitational interaction between inclined, elliptical rings
Authors: Yoder C.F.
Published: July 2016

The gravitational torque between two wire rings or within a ring of finite width can prevent differential precession caused by planetary oblateness. Goldreich and Tremaine (1979) proposed this model to explain the observed eccentricity and width variations of the Uranian ε ring. A general expression for the potential for two elliptical and inclined rings is derived in this paper. The stationary solutions and stability of this system are briefly examined.
Applications of three-body resonances to satellites and planetary rings
Authors: Aksnes Kaare
Published: July 2016

Formulas have been derived for the strengths and libration/ circulation characteristics of resonances for which qn1- (p+q)n2+ pn3= 0, where p and q are integers and n1, n2, and n3are the mean motions of any three gravitationally interacting bodies in coplanar orbits.

The formulas are applied to the well known Laplacian satellite resonances as well as to other possible 3-body resonances in the satellite and ring systems of Jupiter, Uranus, and Saturn.
On planetary rings as sources and sinks of magnetospheric plasmas
Authors: Ip W.-H.
Published: July 2016

The presence of satellite and ring systems in the magnetospheres of Jupiter, Saturn and Uranus introduces interesting new physical effects affecting the general dynamics and compositions of these magnetospheres. Besides acting as a sink for the magnetospheric particles via solid-body absorption, the satellites and rings could also emit neutral and ionized gas into the magnetospheres. In the case of the Saturnian rings, because of their especially broad structure and close proximity to the planet, strong exospheric and ionospheric couplings can also take place. Several observed features (e.g. depletion of the ionospheric electron content, generation of the atomic hydrogen cloud in the vicinity of the rings, and a discontinuity in optical depth at 1.64 Rsin the B ring) of the ionosphere and the ring system could result from the related processes of mass transport and exchange between the ionosphere and the rings. Similar effects may also occur in the region of the tenuous E ring leading to peculiar equatorial confinement of the corotating thermal plasma there.
The E-ring of Saturn
Authors: Smoluchowski R.
Published: July 2016

The origin of the E-ring of Saturn and its relationship to Enceladus is a well known problem. Rather than assuming that the ring was formed as a result of one big impact long ago or that it is a consequence of ejection of subcrustal water by tidally induced stresses and cracks of the satellite, it is proposed that the ring is formed as a consequence of micrometeoritic and meteoritic bombardment of Enceladus. It is shown that the mass reaching the ring replaces that lost by erosion, drag and other mechanisms. The effect of the presence of amorphous ice and the possible opposition effect is indicated.
Collisional outcomes in the asteroid belt
Authors: Farinella P. , Paolicchi P. , Zappala V.
Published: July 2016

The importance of catastrophic collisions as an evolutionary process determining the main physical properties of asteroids has been recognized since a long time, but only recently its central role against other evolutionary mechanisms, such as accretion or small-scale cratering phenomena, has become apparent. For catastrophic collision we mean a major impact event, causing extensive rupture of the target's solid-state cohesion and ejection of large broken fragments. According to the laboratory impact experiments performed by Fujiwara et al. (1977), a high-velocity collision can result into a variety of different outcomes, depending mainly on the specific energy delivered to the target by the projectile body. These outcomes can range from cratering to spallation to complete disruption, with different velocities of the ejected material in the various cases. When we try to extrapolate these results to real asteroids, we must take into account the fact that, in order to cause the collisional disruption of the target object, a breakup of the solid-state strength is not enough, because in most cases the self-gravitational binding is not negligible. Since this latter depends on the target size, a further differentiation of the collisional outcomes arises. For instance, when the target's gravity is not overcome by the ejection kinetic energy of at least a part of the fragments, the final outcome of the collision is a peculiar object which cannot be obtained by laboratory experiments, i.e., a “rubble pile” reaccumulated asteroid,held together by its own self-gravitation (Davis et al., 1979; Farinella et al., 1981; Weidenschilling, 1981; Farinella et al., 1982).
The Evolution of Meteor Streams
Authors: Fox Ken , Williams Iwan P.
Published: July 2016

If one regards a ring system as a family of particles moving on coherent orbits which may be influenced by the gravitational perturbations of a secondary.then a meteor stream is a good example of a ring system. Of course, there is a difference in that the eccentricity and inclination of meteor streams are significantly higherthan any found in ring systems about planets. Nevertheless, it may be instructive to consider briefly the evolution of meteor streams. One advantage of studying meteor streams is that observational data is available over a considerable period (at least 100 years in all cases and in excess of 1000 years for streams like the Perseids, Eta Aquarids and Orionids).
The Bulk Radio Expansion of Cassiopeia A
Authors: Green D.A.
Published: July 2016

Comparison, in the visibility plane, of radio observations of Cassiopeia A made at 151 MHz over a 2.3 yr interval indicate that the bulk of the radio emitting material has not been decelerated strongly.
3C58’s Filamentary Radial Velocities, Line Intensities, and Proper Motions
Authors: Fesen R.A. , Kirshner R.P. , Becker R.H.
Published: July 2016

Optical spectroscopy on nearly 50 filaments of 3C58 indicates a maximum expansion velocity of 1100 ± 100 km s−1. A considerable range in radial velocity with projected distance from remnant center is found suggesting that the remnant’s optical emission is not confined to a thin shell. Typical filament electron densities are between 200 - 500 cm−3 with Hα/[N II] ratios in the range 0.2 - 0.5. Optical extinction to 3C58 is modest with E[B-V] = 0.68±0.08. Preliminary radial proper motion measurements for a few outlying filaments suggest values of order 0.05” - 0.07” yr−1.
Overview of the Interstellar Medium: Supernova Related Issues
Authors: Cox Donald P.
Published: July 2016

Establishing that the interstellar pressure is higher than usually realized and that the magnetic component is probably dominant, I propose a drastic revision for our understanding of the interstellar landscape.
The Effects of Progenitor Mass Loss on the Properties of a Supernova Remnant
Authors: Lozinskaya T.A.
Published: July 2016

Observations of ring nebulae around WR and Of stars, including those in OB associations, have been used to give information on the pre-supernova environment.
Models for X-ray Emission from Tycho’s Remnant
Authors: Smith Barham W. , Jones Eric M.
Published: July 2016

We reexamine the X-ray emission from Tycho’s remnant using results from hydrodynamic models computed with a detailed spherically symmetric code. The observed synchrotron radio contours (Green and Gull 1983) appear to require a cloudy circumstellar medium (Dickel and Jones, 1985; Dickel, Eilek, and Jones 1987), thus we explore the X-ray emission properties of similar models. We find that they tend to produce broad shells of X-ray emission that resemble the observed X-ray map of Tycho (Seward, Gorenstein, and Tucker 1983). A simple hydrodynamic model can satisfy both radio and X-ray observations, but it has little similarity to the evolution of remnants in cloudy media dominated by thermal conduction (McKee and Ostriker 1977). More work needs to be done to ensure that the spectrum as well as the X-ray map can be modeled with the same cloudy circumstellar medium, although we believe it will not be difficult to obtain as good a statistical agreement with the spectral data as other models have achieved (e.g. Hamilton, Sarazin, and Szymkowiak 1986).
Limits on the Presence of Sulfur in the Young SNRs LMC N132D and SMC 1E0102.2-7219
Authors: Lasker Barry M.
Published: July 2016

A new area-spectroscopy search for sulfur as a tracer of the “Si Group” of elements in the ejecta of the young SNRs, LMC N132D and SMC 1E0102.2–7219, yields negative results for [S II]λλ6719, 6731 and [S III]λλ9064, 9532.
G18.95-1.1, A Composite Supernova Remnant Interacting with the Ambient Interstellar Medium
Authors: Fürst E. , Reich W. , Hummel E. , Sofue Y.
Published: July 2016

New radio continuum and spectral line observations of the Galactic radio source G18.95-1.1 are reported. The distance to G18.95-1.1 is 2 kpc as derived from HI-21 cm spectral line observations. These data also indicate an interaction with the interstellar medium. The radio continuum observations classify G18.95-1.1 as a composite supernova remnant.
Effect of Ambient Density on Statistical Properties of SNRs: Σ-D Relation, N-D Relation, Energy Content
Authors: Berkhuijsen Elly M.
Published: July 2016

Variations in ambient density can largely account for: slope and extent of the observed Σ-D relations, the slope of about +1 of the cumulative N-D relation, and the increase of Eo with D as derived from optical line data. Emin increases during the evolution; the behaviour of Ex remains uncertain.
A Search for Shells around Crabs
Authors: Becker R.H. , Helfand D.J.
Published: July 2016

Prior to conducting a survey of the galactic plane at 327 MHz using the VLA, we have imaged four fields near galactic longitude of 20 degrees. Each image will cover a 2.5 degree field with ∼1 arcmin resolution. The fields have been chosen to include the remnants G20.0-0.2, G21.5-0.9, and G24.7+0.6. The first two are isolated Crab-like objects, that is, there is no discernible associated shell. Since such shells have relatively steep spectra, images at 327 MHz will be more sensitive to their presence. The absence of a shell can constrain the density of the ISM in the vicinity of the SNR (Reynolds and Aller 1985 A.J.90, 2312). Since ∼50% of Crabs are naked, the implications can be extended to a significant fraction of the ISM.
IRAS Observations of Collisionally Heated Dust in Large Magellanic Cloud Supernova Remnants
Authors: Graham James R. , Evans A. , Albinson J.S. , Bode M.F. , Meikle W.P.S.
Published: July 2016

IRAS additional observations show that luminous (104−105 L⊙) far-IR sources are associated with the Large Magellanic Cloud (LMC) supernova remnants N63A, N49, N49B, and N186D. Comparison of the IRAS and X-ray data shows that a substantial fraction of the IR emission from three of the SNRs can be accounted for by collisionally heated dust. The ratio of dust-grain cooling to total atomic cooling is ~10 in X-ray emitting gas (T~106 K). We show why dust cooling does not dominate, but probably speeds SNR evolution in an inhomogeneous interstellar medium.
IC 443: The Interaction of a SNR with a Molecular Cloud
Authors: Burton Michael G.
Published: July 2016

Observations are presented of shocked line emission from H2, CO and HCO+ molecules in the SNR IC 443. IC 443 is the most luminous galactic H2 emission line source yet discovered. The implications for physical processes in shocked molecular gas are discussed.
Differential Imaging of [Fe X] in IC 443
Authors: Brown Larry , Woodgate Bruce E. , Petre Robert
Published: July 2016

This paper presents images of two areas of the supernova remnant IC443 showing emission from the [Fe X] 6374Å red coronal line taken with an emission line differential imaging camera. The areas are in the vicinity of strong soft X-ray emission as observed with the Einstein Observatory. The [Fe X] emission is patchy on the scale of seconds of arc. For the highest emission regions we find an electron density of approximately 100 cm−3 and gas pressures of 108cm−3K. No correlation is found between the X-ray and [Fe X] knots, and the results support a clumpy, multi-temperature region where the [Fe X] knots are balanced between collapse and evaporation.
Supershells
Authors: McCray Richard
Published: July 2016

Repeated supernovae from an OB association will, in a few ×107 yr, create a cavity of coronal gas in the interstellar medium, with radius > 100 pc, surrounded by a dense expanding shell of cool interstellar gas. Such a cavity will likely burst through the gas layer of a disk galaxy. Such holes and “supershells” have been observed in optical and H I radio emission maps of the Milky Way and other nearby galaxies. The gas swept up in the supershell is likely to become gravitationally unstable, providing a mechanism for propagating star formation that may be particularly effective in irregular galaxies.
Self-Regulating Star Formation in Isolated Galaxies
Authors: Parravano Antonio
Published: July 2016

Recent investigation (Parravano, 1987) shows that the diffuse phases of the ISM condense mainly by the transition from warm gas to small cool clouds (WG → SC). In this work we introduce the new hypothesis that the star formation rate (SFR) in isolated galaxies is self-regulated in such a way that it maintains Pmax close to the ISM gas pressure. Here Pmax is the gas pressure at the marginal state of stability for the transition WG → SC. This hypothesis leads to a relation between global galactic parameters which appears to be applicable to various morphological groups of isolated galaxies.
Ultraviolet Fe II Absorption Lines in HD 59643
Authors: Eaton Joel A.
Published: July 2016

The peculiar red giant HD 59643 (C6,2) has a composite spectrum like a symbiotic star’s except for the absence of highly ionized species. UV observations show a highly variable hot continuum with superimposed absorptions of Fe II and the common emission lines of C IV, Si III], C III], C II], and Mg II. These Fe II absorptions, which are practically ubiquitous in interacting binaries, are an effective diagnostic of turbulence and distribution of scattering gas, even at low resolution.
Orbital Radial Velocity Curves of Symbiotic Stars
Authors: Garcia Michael R. , Kenyon Scott J.
Published: July 2016

For the past 6 years we have been measuring the radial velocity of the M-giant component of Symbiotics Stars with high dispersion echelle spectrographs. Because these velocities are based on the absorption line spectrum of the M-star, very reliable orbital radial velocity curves can be constructed. The orbital solutions derived from these velocity curves allow the approximate size of the binary to be determined, and also provide insight into the origin of the photometric variations seen in these stars. For most of the stars, the photometric variations are due to eclipse or reflection effects (two notable exceptions are Z And and RW Hya). Stars which may be near to filling their Roche lobes are TX CVn, Z And, EG And, UV Aur, and CI Cyg. Stars which do not appear to fill their Roche lobes are AG Dra, RW Hya, and AG Peg.
The Present State of Symbiotic Polarimetry
Authors: Schwarz Hugo E. , Aspin Colin , Magalhaes A.M. , Schulte-Ladbeck R.E.
Published: July 2016

We present preliminary statistical results of an ongoing polarimetric survey of symbiotics. So far, 38% of the known symbiotics have had their polarization measured at least once. About 40% of S and D types show some intrinsic polarization while only one of the five measured D’ types is polarized. R Aqr is still the only symbiotic with strong, variable polarization.
Emission Line Ratio Classification of Symbiotic Stars
Authors: Schwarz Hugo E.
Published: July 2016

A 2-dimensional classification system for symbiotic stars based on the 5007/4861 and 3727/5007 line ratios adapted from the method of Baldwin et al.(1981) is presented. It is shown that a simple measurement suffices to classify stars and no reddening has to be taken into account. Symbiotics fall into 2 distinct classes in the line ratio plot. The dusty and S types. Neither type coincides with either the planetary nebulae or the HII region locus. The highest excitation is found for the dusty types. The two dimensional distribution can be interpreted as evolutionary, the more evolved Mira containing symbiotics lying closer to the PN locus. The fact that there are few D, D’ type symbiotics would indicate that the phase between Mira and PN is short.
Resonance Line Profiles from Radial Accretion Flows
Authors: Tylenda R.
Published: July 2016

A compact star in a detached binary system can accrete the matter from the stellar wind of the companion. In this case a more or less radial accretion flow is formed. By analogy to stellar winds from early type stars it is usually believed that the accretion of this sort should produce inverse P-Cygni profiles in resonance lines. However, there are physical differences between the wind and the radial accretion which can alter the outgoing profile significantly.

The matter outflowing from an early type star cools off very fast due to the adiabatic expansion. However, it remains highly ionized as the quickly decreasing density does not allow it to recombine. Therefore the principal mechanism for the resonance line formation here is the scattering of the stellar continuum photons in the wind.
Colliding Winds in Symbiotic Systems
Authors: Kwok Sun
Published: July 2016

The physics of colliding winds in symbiotic systems is reviewed. The theoretical predictions are compared with observational data of symbiotic novae, in particular the recently erupted system HM Sge. It is suggested that the spectral behaviour of HM Sge from X-ray to radio can be explained by the colliding winds process.
Thermonuclear Runaway Models for Symbiotic Novae
Authors: Kenyon Scott J.
Published: July 2016

This paper reviews the basic physics of thermonuclear runaways on the surfaces of accreting white dwarf stars, with a special emphasis on understanding the evolution of symbiotic novae.
AG Dra a Symbiotic Star With an Uncommon Cool Component
Authors: Friedjung M.
Published: July 2016

AG Dra is probably a metal poor symbiotic binary of the galactic halo. The luminosity of the cool component is uncertain, which contributes to doubts about the correct model. Behaviour in activity is non classical with high ionization emission lines still having been seen then in the spectrum. This may perhaps most easily be explained by a weak thermonuclear event.
CH CYG : Ten Years of Activity
Authors: Selvelli P.L.
Published: July 2016

The results of multi-frequency observations of CH CYG during the last outburst are reviewed, and the time-sequence of the variations related to the jets formation is discussed.
The Formation and Evolution of Symbiotic Stars
Authors: Webbink R.F.
Published: July 2016

The evolutionary origins of symbiotic stars containing (i) disk-accreting main sequence stars, (ii) wind-fed, shell-burning white dwarfs, and (iii) disk-accreting neutron stars are described. Of particular interest are those white dwarf systems which have orbital periods too short to have escaped tidal mass transfer prior to becoming symbiotics. We show here that, under suitable circumstances, low-mass, long period binaries may undergo quasi-conservative mass transfer, rather than evolving through common envelope evolution to the cataclysmic variable state, thus accounting for the existence of these systems. Approximate expressions are given for the lifetimes, and relative efficiencies (mass accreted/mass of donor) for different modes of interaction among symbiotic binary systems.
Recurrent Novae
Authors: Livio Mario
Published: July 2016

An examination of the existing observational material on all the objects classified as recurrent novae, reveals that only T Pyx, U Sco, T CrB and RS Oph deserve such a classification. We review the properties of outbursts powered by thermonuclear runaways and accretion events and determine their observational consequences. We conclude that the outbursts of T CrB and RS Oph are very probably caused by accretion events from a giant companion onto a main sequence star. The outbursts of T Pyx and U Sco may be powered by thermonuclear runaways on the surface of white dwarfs with masses close to the Chandrasekhar limit. However, some questions, in particular regarding the composition of the accreted material in U Sco remain to be answered.
Contributions and Prospects for Spectral Classification of Stars with Objective Prism Techniques
Authors: Kharadze E. K.
Published: July 2016

The following topics will be discussed: a) A few historical comments; b) MK classification - the most important stage of classification work; c) Recently revealed peculiarity features and the problem of further differentiation of the classification scale; d) Classification work in the USSR; e) The role of classification results with respect to galactic structure studies; f) Low dispersion spectra and faint M-type stars and the missing mass problem; g) Extraterrestrial spectral observations: new promising means for research.
A New Objective Prism Catalogue of OB and Supergiant B, A, F and G Stars in the Magellanic Clouds
Authors: Philip A. G. Davis , Sanduleak N.
Published: July 2016

The Michigan Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory has been used with the “thin” prism (Blanco 1974) to survey the Large and Small Magellanic Clouds. Four plates, covering approximately 90 square degrees, and three plates, covering approximately 70 square degrees, were taken of the Large and Small Magellanic Clouds respectively. One hour exposures on nitrogen baked, IIIa-J plates were obtained. The limiting magnitude of the plates is V = 16 mag. At the dispersion of 1360 Å/mm OB stars can be recognized by their long uv extension, in which no sign of a Balmer discontinuity can be seen. The supergiants can be recognized by the appearance of a Balmer discontinuity and classified into temperature types by the strength of the hydrogen lines.
Problems and Prospects of Multicolor Stellar Photometry
Authors: Straižys V.
Published: July 2016

Intermediate band multicolor photometry now is one of the principal methods to obtain information on stellar temperatures, luminosities, metallicities, peculiarities and interstellar reddenings. The method has some advantages over the method of stellar classification by visual inspection of low dispersion spectral images:
Golay Stellar Boxes in the Strömgren Four-Color System
Authors: Philip A. G. Davis , Egret D.
Published: July 2016

Hauck and Mermilliod (1978) have compiled a new catalogue of approximately 20,000 observations in the Strömgren four-color system. Using the facilities of the Stellar Data Center in Strasbourg, Egret and I have revised the computer program that dereddens the indices to take into account recent revisions made by Crawford (1978) in the routines for handling B stars. Then, following the method of Golay (1978), we have constructed stellar boxes in the four-color system.
Quantitative Spectral Classification of Be Stars on Low Dispersion Spectra
Authors: Divan Lucienne
Published: July 2016

Two separate Balmer jumps are observed in some Be stars. The first one, in absorption and unchanging, is attributed to the central star and gives its spectral type and luminosity class in the λ,D system. The second one, occuring at shorter wavelengths, either in absorption or in emission, originates in layers at a low pressure. It is shown that these layers modify the colors of the central star on both sides of the Balmer jump and that they are not optically thin even in the continuum.
Automatic MK Spectral Classification. I. Early Type Stars
Authors: Mendoza Eugenio E.
Published: July 2016

A scheme of automatic MK spectral classification is presented. It is based upon standard spectrograms obtained for visual spectral classification. Computer results are given for all the MK standard stars earlier than Bl. They are well correlated with the MK system. However, the results might be improved by using a rapid-scanning Michelson Fourier Transform Spectrophotometer to obtain the stellar spectra. The analysis of the interferograms should also be made by a computer.
The Problem of the 2200 Å Feature
Authors: Nandy K.
Published: July 2016

In my earlier work (Nandy, 1977) I have described an ultraviolet photometric system which involves a two dimensional stellar classification. This system is based on constructing broad band (Δλ ≈ 100 Å) ultraviolet colors (m2700 - V), (m2190 -m2740) and (m1500 - V) from the low dispersion S2/68 spectra. This photometric system is suited ideally to extend the classification to stars fainter than V = 6m.0, because the spectral features as described by the previous speaker, A. Cucchiaro, are not easily identifiable in these spectra.
A Summary
Authors: Blanco V. M.
Published: July 2016

This has been a timely conference. Astronomical spectroscopic classification is facing crossroads that make it wise for us to look carefully at where we are now and which way we should go. The on-going explosion in detection techniques for fainter and fainter objects at all wavelengths and the availability of fast analytical procedures are opening up these new roads. It is a tribute to Fr. Patrick Treanor’s vision that we have gathered here to take stock of the current status and to consider the future of spectral classification and it was fitting that we did so while remembering the pioneering work of Fr. Angelo Secchi
Classification Based on 102/Å/mm Objective Prism Spectra
Authors: Clausen J.V. , Jensen K.S.
Published: July 2016

Equipped with a 15° F2 objective prism the (45/77/150)cm Schmidt telescope of the Copenhagen university Observatory, Brorfelde yields spectra of 102 A/mm at Hα to a limit of approximately mpg =9.5.
Initial Results With the Objective Prism of the Uk Schmidt Telescope
Authors: Brück M. T.
Published: July 2016

The U. K. 1.2m Schmidt objective prism with its small apex angle (23’12”) and high ultraviolet transmission is a particularly powerful tool for the study of faint objects. It has been shown that objects of 20m and fainter can be reached on a 60 minute exposure of unwidened spectra on hypersensitized IIIa-J emulsion. A description of the prism and its performance has already been published (Nandy et al. 1977).
Star Classification Through Photographic Broadband Photometry With Kodak Fine-Grain Emulsions
Authors: Buser R.
Published: July 2016

The recently developed Kodak emulsions IIIa-J and IIIa-F have been used as a new tool for deep-survey photometry. Among their most useful features are the following: (i) fine to very fine granularity; (ii) very high resolving power; (iii) high sensitivity over a large wavelength range in the optical part of the spectrum.

Some numerical results obtained from scanner data of a variety of normal star types, and from the spectral sensitivities of these Kodak plates combined with various optical filters are presented. We study the effects of these filters on the resulting synthetic colors with respect to the intrinsic potential of the colors to classify faint stars. In addition we briefly discuss the effects of interstellar reddening and the calibration of the photographic colors through photoelectric UBV photometry.

This synthetic approach to multicolor photometry is discussed in the more general context of the relations between spectral classification, stellar photometry, and model atmosphere calculations. This context is the natural basis for galactic astronomy.
Recurrence Behaviour of Outbursts in VW Hyi
Authors: Van Der Woerd H. , Van Paradijs J.
Published: July 2016

The recurrence behaviour of normal- and super-outbursts in the SU Uma system VW Hyi is consistent with the idea that every superoutburst is triggered by a normal outburst. A simple description with a constant relaxation period of 170 days for the recurrence of superoutbursts, together with a randomly occurring trigger (the normal outbursts’) is presented.
Photometry of BD −7° 3007
Authors: Shylaja B.S.
Published: July 2016

Photometric observations of BD −7° 3007 in B and V filters are reported. Rapid flickering appears to be present at all phases, implying an unfavourable angle of inclination of orbit for seeing eclipse effects. A modulation of the light curve of period about an hour is present only on one night. The continuum energy distribution agrees with that of ß Com (GO V) in the longer wavelength region only.
Properties of the Optical 2-Second Oscillations in E1405−451
Authors: Larsson S.
Published: July 2016

The AM Her type system E1405−451 is known to show 1 - 3 second variability in its optical emission. Our observations show this variability to be due to quasi-periodic oscillations with a coherence time on the order of one minute. The observations also reveal variations in the color of the oscillating light source. These variations are difficult to explain with present cyclotron emission models.
Simultaneous Five Color (UBVRI) Polarimetry of VV Puppis
Authors: Piirola V. , Reiz A. , Coyne G.V.
Published: July 2016

Observations of linear and circular polarization in five colour bands during a highly active state of VV Puppis in January 86 are reported. A strong linear polarization pulse with the maximum in the blue, PB ≈ 22%, is observed at the end of the bright phase when the active pole is at the limb and a weaker secondary pulse, PB ≈ 7%, is seen in the beginning of the bright phase, when the active pole reappears. Strong positive circular polarization is also observed in the blue and the ultraviolet, РU ≈ PB ≈ 18%, PV ≈ 10% during the bright phase. The circular polarization reverses the sign in the B and V bands during the faint phase and a negative polarization hump is seen when the active pole crosses the limb. The circular polarization in the V band reaches the value PV ≈ −10% at the hump, after which it remains near PV ≈ −5% during the faint phase. This is probably due to radiation coming from the second, less active pole and accretion thus takes place onto both poles. The wavelength dependences of the positive and negative parts of the circular polarization curve are different and no polarization reversal is seen in the U band. The position angle of the linear polarization is well determined during a large portion of the cycle, especially in the V band, thanks to the activity from both poles. A best fit to the position angle curve, taking into account also the duration of the positive circular polarization phase interval ΔΦ = 0.40 (in the V band), yields the values of orbital inclination i = 78° ± 2° and the colatitude of the active magnetic pole ß = 146° ± 2°. The relatively good fit to the position angle data indicates that the simple dipole model is nearly correct in the case of VV Puppis. Some wavelength dependence is, however, seen in the position angle curves, especially in the I band where the slope Δθ/ΔΦ at the main pulse is considerably smaller than in the other bands. The shape of the position angle curves changes also in the blue and the ultraviolet around the middle of the bright phase. This is probably due to optical thickness effects as the side of the accretion column which is toward the observer changes near this phase.
Multi-Frequency Observations of the 1985 Outburst of RS Ophiuchi
Authors: Snijders M.A.J.
Published: July 2016

The 1985 outburst of the bright, recurrent nova RS Oph was almost simultaneously observed at X-ray, UV, optical, IR and radio frequencies at many epochs. The abundances in the ejected shell and the development of the bolometric luminosity as a function of time suggest that the cause of the outburst is a nuclear runaway on a massive white dwarf.
Exosat Observations of X-Rays from Classical Novae during Outburst Stage
Authors: Ögelman H. , Krautter J. , Beuermann K.
Published: July 2016

The initial discovery of soft X-rays from Nova Muscae 1983 was followed by eight additional observations of the three brightest novae whose outburst stage coincided with the lifetime of EXOSAT satellite; namely three more observations of Nova Muscae 1983, three observations of Nova Vulpeculae 1984 # 1 (PW Vul), and two observations of Nova Vulpeculae 1984 # 2. Through these observations we sampled the soft X-ray light curve of classical novae from optical maximum to ~ 900 days after. The observations seem best explained by the constant bolometric luminosity model of a hot white dwarf remnant. Although the measurements suffer from limited statistics, very broad energy bandpass, and incomplete sampling of any single nova, their constraints on the theories of nova outburst are significant. One constraint is that the lifetime of the white dwarf remnant in Nova Muscae 1983 is ~ 2 to 3 years, which leads to the conclusion that the burned envelope mass Mburn should be of the order of . The second constraint is that the maximum temperature, of the white dwarf remnant should approximately be within 200 000 K to 400 000 K. We estimate that a white dwarf remnant evolving like the central star of a planetary nebula, with core mass of 0.8 to 0.9 M⊙, core luminosity of ~ 2 × 104L⊙, and envelope mass of 10−6M⊙, can explain the general characteristics of the X-ray measurements for Nova Muscae 1983. In order to have ≥ 1.1 M⊙ core mass, estimated from the early observations of bolometric luminosity in the UV to infrared range, a wind with Ṁ ≤ 5 × 10−7M⊙yr−1 appears to be necessary. The few observations of Nova Vulpeculae 1984 # 1 and Nova Vulpeculae 1984 # 2 , during the first year after outburst, give a risetime and intensity that is consistent with a constant bolometric luminosity model.
On the Computation of Accretion Disk Spectra
Authors: La Dous C.
Published: July 2016

Spectra of accretion disks in dwarf novae and some novalike stars have been computed. Many simplifications to the general model of the nature of a cataclysmic variable are needed to make the system numerically tractable. The necessity, justification, and implications of such simplifications are discussed together with the influences of some system parameters on the disk radiation.
The May 1985 Superoutburst of OY Carinae: I. Structure of the Outer Disk from Optical and IR Observations
Authors: Naylor T. , Bailey J. , Bateson F.M. , Berriman G. , Charles P.A. , Coulson I.M. , Hyland A.R. , Reinsch K. , Warner B. , Whitelock P.A.
Published: July 2016

We present optical and IR observations of the dwarf nova OY Car during the May 1985 superoutburst. From them we find that the superhump has a temperature of ~8000K and an area of order half the size of the red dwarf or accretion disk. We also compare the behaviour during two simultaneous optical/IR observations. Whilst the light curves in the two pass bands are similar during one observation, in the other observation they show marked differences that may be due to a cool region in the outer disk.
Hot Stripes Rather than Hot Spots in Cataclysmic Binaries: 2 - D Hydrodynamic Models
Authors: Rozyczka M. , Schwarzenberg-Czerny A.
Published: July 2016

Two-dimensional hydrodynamic models of the collision region between the stream and the disk in a cataclysmic binary are presented. The adiabatic collision results in significant mass loss from the system and produces large turbulent regions in outer parts of the disk. Radiative cooling of the collision region leeds to a semi-continuous injection of mass into the disk in the form of dense blobs of gas. In both cases the hot regions obtained as a result of the collision are over 1/6 of the circumference of the disk long and almost 40% of its radius deep, deserving to be renamed ‘hot stripes’.
The Interaction of Nova Shells with the Interstellar Medium
Authors: Duerbeck H.W.
Published: July 2016

Decelerations of the shells around the novae V603 Aql, V476 Cyg, DQ Her and GK Per were determined from photographs and recent CCD observations. The deceleration is larger for higher expansion velocities, the mean half-lifetime, after which the expansion velocity has dropped to half its initial value, is 75 years.
Extremely Slow Nova PU Vulpeculae - Seven Fat Years After Maximum
Authors: Chochol D. , Grygar J.
Published: July 2016

UBV photometry and spectroscopy of the symbiotic nova PU Vul support the suggestion that the system consists of a mass-losing M-giant massive component and a C-O dwarf accreting hydrogen-rich matter, mimicing in outer appearance an F-supergiant.
Spectroscopy of CN Orionis
Authors: Mantel K.H. , Barwig H. , Haefner R. , Schoembs R.
Published: July 2016

Two outbursts and a minimum phase of the dwarf nova CN Orionis have been observed spectroscopically. One outburst was covered almost completely. The outburst spectra show periodic variations of the absorption lines which are interpreted with the formation of an elliptic disc during outburst stage. During decline from outburst a narrow emission line appears in the core of the broad H« absorption line. The balmer decrement in the outburst phase is much steeper than in the minimum phase. This implies that during the outburst the emission line region is located more outward in the disk. The semi amplitude of the radial velocity curve was determined to Kl = 152 km/s ± 10 km/s. Using the photometric orbital period and an assumption about the inclination angle the approximate system parameters could be derived.
A Modern View of the Dwarf Nova Z Chamaeleontis
Authors: Wade R.A.
Published: July 2016

Some recent photometric and spectroscopic results for this “ultrashort” period system are summarized, and several straightforward consequences of these results for our understanding of the evolution of cataclysmic binaries are pointed out: The space motion of Z Cha is characteristic of the old disk population. The white dwarf cannot be composed primarily of He, unless it grew by accretion by at least 20%. The inferred masses of the component stars, combined with the usual gravitational quadrupole formula, probably do not suffice to explain the inferred rate of mass transfer, even in quiescence. The secondary star does not lie on the computed evolutionary tracks in the period - mass diagram of Paczynski and Sienkiewicz.
The Period and Magnetic Field Distributions of Cataclysmic Variables: Implications for their Evolution
Authors: Schmidt G.D. , Liebert J.
Published: July 2016

Comparison of the period distributions of various classes of CVs confirms an extreme bias of the synchronous AM Her systems toward short orbital periods, while the DQ Her systems do not differ significantly from the distribution of non-magnetic systems. This suggests either strong selection effects or enhanced evolution of the AM Her systems. There is as yet no obvious bimodality in either the magnetic field distributions of isolated white dwarfs or of CV primaries. However, clear differences between the two exist: the strongest being that magnetic primaries are overrepresented among short period CVs by more than an order of magnitude in comparison to the field white dwarfs.
Hydrodynamics of Accretion Columns
Authors: Herold H. , Wolf K. , Ruder H.
Published: July 2016

A detailed understanding of how the infalling matter in accretion columns is decelerated is essential for the calculation of the emitted radiation. On neutron stars, the deceleration takes place mainly by the interaction of the plasma with radiation, at least for the high-luminosity sources. We report on our two-dimensional calculations of the hydrodynamic flow in such accretion columns. The radiation transport is treated in the diffusion approximation, and we are looking for a stationary solution for the velocity field. The dependence of the results on physical parameters, especially on the accretion rate is discussed. Due to the non-linearity of the problem it turns out that only in certain parameter ranges stationary solutions seem to exist. For accretion rates higher than a critical value there are no stationary accretion flows. This leads us to the conclusion that a time-dependent picture for the accretion is unavoidable.
The Energy Distributions of Magnetic Variables: The Effects of Inhomogeneous Accretion Columns
Authors: Stockman H.S. , Lubenow A.F.
Published: July 2016

Previous shock models for the AM Herculis-type magnetic variables have assumed homogeneous accretion columns, with constant infall densities out to a characteristic column radius. The resulting energy distributions are strongly peaked in the visible to ultraviolet and are in disagreement with observations. We report the preliminary results of calculations with more general radial functions of the infall density. Exponential and gaussian profiles yield continua similar to those of the standard model. More tapered, power-law profiles produce continua which are flatter and in better agreement with observations. Comparisons are made to data for AM Her and E2003+225.
Rapid Mass Accretion in the Symbiotic Star AG Dra
Authors: Iijima T.
Published: July 2016

The mass accretion process onto the hot component of AG Dra and its explosive phenomena are discussed. The hot component seems to be a massive white dwarf (M > 1 M⊙). The mass accretion rate is estimated to be about 10−7M⊙/year. Many properties of the explosive phenomena agree with those of mild hydrogen flashes expected from this rapid mass accretion.
Symbiotic Star as 201: a Planetary Nebula
Authors: Kohoutek L.
Published: July 2016

Optical spectrum of AS 201 is presented: this object shows emission lines of moderate excitation (exc.class 5) and absorption spectrum of a G2III star. For the interstellar extinction and distance the values c=0.45 and d=1.5 kpc were estimated. The hot components of AS 2Ol, Cn 1–1 and M 1–2 are located on the Harman-Seaton sequence in the region of evolved central stars of PN. It is suggested that the hot components of some SS are evolved nuclei of PN; high el.density of their nebulae may be explained due to mass loss from the respective cool stars of the binaries.
Cataclysmic Variables - Concluding Remarks
Authors: Kopal Z.Deněk
Published: July 2016

Kitamura sensei, ladies and gentlemen: the remarks which follow will be the last communication by which our colloquium on cataclysmic variables is to be brought to its conclusion; and I appreciate the invitation of its organizing committee to use the remaining time we have together in the congenial atmosphere created for us at Bamberg, in an attempt at a summary of what we heard here in the past few days from several hundred colleagues who gathered here from many parts of the world - to survey the present state of our subject, and consider together where do we go from here. The time for this purpose makes it impossible to touch upon all exciting developments in the field of cataclysmic variables reported at Bamberg in the past few days; but certain general features have emerged from the programme of our colloquium which it may be appropriate to recall.