bluuebunny/crossref_metadata_2025 huggingface dataset:
Far-Ultraviolet and Visible Observations of Flares on dme Stars
Authors: Bromage G E , Patchett B E , Phillips K J H
Published: July 2016

Four large flare events – one on each of the dMe stars UV Cet, AT Mic, EV Lac and EQ Peg – have been witnessed during a total of 17½ hours of far-UV (λλ1150-1950) IUE exposures. Some observational characteristics of these four events are compared. Two showed strong
enhancements of chromospheric and transition-region line strengths. The other two did not, even though their visible flares were intense (ΔU ~ 2 mag). The brightest UV flare spectrum (EQ Peg) is contrasted with that of the largest solar flare seen from ‘Skylab’.
Migrating Waves in Solar-Type Short-Period Eclipsing Binaries
Authors: Milano L. , Russo G. , Mardirossian F. , Mancuso S.
Published: July 2016

One of the properties of RS CVn-like binaries is the presence of cyclic fluctuations, sometimes called “migrating waves”, in the V and other broad-band lightcurves. These fluctuations, perhaps due to spots, vary in amplitudes and periods, in the sense that, the longer the orbital period of the RS CVn system, the higher the amplitude of the “wave”, which may be up to 30-35% of the total light variation. Therefore, in short-period (less than one day) RS CVn binaries, these
fluctuations are generally difficult to be detected.
Activity Correlations in Close Binary Systems
Authors: Basri Gibor , Laurent Robert
Published: July 2016

The best way to learn about the detailed physical conditions associated with stellar activity is to construct detailed self-consistent model stellar atmospheres based on the wide range of diagnostics now available. A quicker rough analysis of the activity can be accomplished by studying the interrelations of the various diagnostics. Tight correlations between diagnostics suggest physical association, and the power law indices of the correlation can help to elucidate the general physical relation the diagnostics have with each other. Our aim in this study was to observe with the IUE satellite a homogeneous sample of stars for which there is extensive coronal data. The X-ray studies of close binaries by Walter and Bowyer (1981) and Walter (1982) provided such a sample; these stars are also accessible to the IUE because of their tendency to strong activity. Because of intrinsic stellar variability, this type of study is best carried out when all diagnostics are measured simultaneously. We have come fairly close to this ideal; only the coronal data is non-contemporaneous for most of the sample. Our reduction of the IUE data is quite similar to that of Ayres, Marstad and Linsky (1981, hereafter AML) and we have used essentially the same diagnostics.
Angular Momentum Loss and the Formation of W UMa Systems
Authors: Budding E.
Published: July 2016

Angular momentum loss (AML) may be introduced as part of the explanation of the peculiar overabundance of W UMa-type contact binaries (W UMS) (for a recent review, see Vilhu, 1981). Among the various possible mechanisms to achieve this are (i) overflow through the outer (L2) Lagrangian point in a deep contact phase (Kuiper, 1941; Nariai, 1979), (ii) magnetic braking, where magnetic lines of force “stiffen” and thus enhance the efficiency of angular momentum loss associated with a stellar wind (Huang, 1966; Mestel, 1968). Such subjects have been investigated in a number of more recent detailed studies.
A Bright Spot and a Serendipitous Stellar Flare on the Contact-Binary VW Cep
Authors: Egge K.E. , Pettersen B.R.
Published: July 2016

Almost twenty years ago a large flare event was observed on the prototype contact binary W UMa by Kuhi (1964). Similar events have been reported on 44 i Boo (Eggen 1948) and U Peg (Huruhata 1952) . In this paper we present photoelectric observations at three wavelengths of a flare on VW Cep. This is the first event of this kind to be reported for this star. VW Cep is a triple system. The main contributor to the visual flux is the eclipsing binary, consisting of a Kl primary and a G6 secondary (Kopal 1978), classified to be in contact. The orbital period is 6h 41m. Seven per cent of the total flux in the visual filter is due to the third component, a late K type dwarf at a distance of 12 AU from the eclipsing system (Hershey 1975).
Empirical Models of Stellar Flares: Constraints on Flare Theories
Authors: Kodaira K.
Published: July 2016

A review is presented on empirical flare models of UV Cet type stars based upon optical,UV, X-ray, and radio observations. The observational constraints on the flare energetics, nature of radiation sources, and flare structures are discussed, with special attention to the geometrical dimension and the magnetic field of the flaring region. The hot-plasma model in the solar analogy is critically examined by comparing it with observations. Possible future observations are suggested to tighten the constraints on the stellar flare theories.
Orientation of a Satellite Located at the Libration Point in the Restricted Three-Body Problem
Authors: Duliński Grzegorz , Maciejewski Andrej J.
Published: July 2016

In this paper the initial results of an investigation of the motion of a rigid body located at the libration point in the planar, restricted three-body problem are given. This problem was analyzed in part by Kane and Marsh (1971), Markeev (1967a,b). However the present investigation is formulated in terms of hamiltonian mechanics. The final results will by used to study nonlinear effects connected with the gravitational influence of the “second” central body.
Steady State Number of the Extinct Comets in High-Inclination Orbits
Authors: Nakamura Tsuko
Published: July 2016

Steady state number of the short-period(SP) comets captured from nearly parabolic(NP) orbits with 60°≤ i(inclination) ≤ 120° and 0.5≤q (perihelion distance) ≤1.5 AU is calculated. Due to smallness of the q and slowness of the capture process, almost all these SP comets become completely extinct. Combining annual flux of the observed NP comets of high inclination with the capture probability from NP to SP orbits and the ejection rate in SP orbits obtained by Monte Carlo simulations, we find that the steady state number of the extinct SP comets in high-inclination orbits is at least 1-2 hundred. If this number can be considered to correspond to the observed one of Apollo-type objects with i ≥ 60°, it is concluded that only less than a few percent of extinct comets leaves sizable non-volatile cores or shells. The number of asteroid-like bodies deduced from the extinct comets with small perihelion distance and high inclination has less ambiguity than that of low inclination, because contribution from asteroid belt is negligible and the source comets are visible(free from observational selection) through the whole course of orbital evolution.
Orbital Evolution of Trojan Asteroids
Authors: Érdi Bálint
Published: July 2016

The motion of the orbits of Trojan asteroids are investigated. Four asteroids around L5 are shown to have librating perihelion. A criterion for the libration of the perihelion is derived and expressed by the initial conditions. This criterion is solved for the initial conditions in two special cases. Thus regions in the configuration space of the initial conditions yielding libration of the orbits of Trojan asteroids are established.
Low Velocity Encounters of Minor Bodies With the Outer Planets
Authors: Carusi A. , Perozzi E. , Valsecchi G.B.
Published: July 2016

Previous studies of close encounters of minor bodies with Jupiter have shown that the perturbations are stronger either if the encounter is very deep or if the velocity of the minor body relative to the planet is low. In the present research we investigate the effects of low velocity encounters between fictitious minor bodies and the four outer planets. Two possible outcomes of this type of encounter are the temporary satellite capture of the minor body by the planet, and the exchange of perihelion with aphelion of the minor body orbit. Different occurrence rates of these processes are found for different planets, and the implications for the orbital evolution of minor bodies in the outer Solar System are discussed.
Recent increase of the activity of the symbiotic star CH Cygni
Authors: Chochol Drahomir , Hric Ladislav
Published: July 2016

CH Cyg has exhibited a great deal of activity in the recent times. We obtained two spectra with dispersion of 9 A/mm with the 2 m telescope of the Ondrejov Observatory on the nights of July 4/5 and August 6/7, 1981. The differences between these spectra are conspicuous. The description of the spectral changes during this period follows:

The Balmer lines became broader, the R wing of the early Balmer shell lines being partly suppressed by absorption. The inverse P Cygni profiles became apparent from H8 to H30.
Observations of Local Interstellar Mg I and Mg II
Authors: Bruhweiler F. , Oegerle W. , Weiler E. , Stencel R. , Kondo Y.
Published: July 2016

We have combined Copernicus and IUE observations of 5 stars within 50 pc of the Sun to study the ionization of magnesium in the local interstellar medium (LISM). The high resolution Copernicus spectrometer was used to detect interstellar Mg I 2852 in the spectra of α Gru, α Eri, and α Lyr, while placing upper limits on Mg I in the spectra of α CMa and α PsA. Observations of Mg II 2795, 2802 for these stars were also obtained with IUE and Copernicus. The column densities of Mg I and Mg II are used to place constraints on the temperature of the LISM.
FeII and MgII in the nearby Interstellar Medium
Authors: de Boer Klaas S. , Lenhart Heinz
Published: July 2016

UV spectra with 15 km s-1 resolution of bright stars have been searched for Fell and Mgll interstellar lines. We present equivalent widths of absorption for 8 stars and find average line-of-sight densities n(FeII)= 4 10-8 and n(MgII)= 2 10-7 cm-3 . This represents approximately n(H)= 0.03 cm-3.
Dark Cloud and Globule Distribution for Galactic Longitudes 230 to 360 Degrees
Authors: Feitzinger J.V. , Stuewe J.A.
Published: July 2016

A catalogue of dark nebulae and globules has been compiled from a study of the ESO-B and SRC-J sky atlas for galactic longitudes 230°<1<360°. This catalogue closes the great southern gap open since the work of Lynds (1962), We have listed 489 dark nebulae and 311 globules. The catalogue contains positions, sizes, opacities and the van den Bergh classification (1972) on the filamentary morphology of dark clouds. We present statistics concerning the northern and southern distributions and sizes of the nebulae.
Polarization of Radio Molecular Lines and Mapping of Magnetic Field Direction
Authors: Deguchi Shuji , Watson William D.
Published: July 2016

Two level calculations by others for the linear polarizations expected for molecular emission lines from interstellar clouds are extended by considering a number of coupled rotational states of a diatomic molecule. Higher transitions commonly have strengths comparable with that of the J=1-0 transition so that depolarization due to coupling between the various J-states might be expected to reduce the predicted linear polarization. The significance of the null observational results obtained recently by Wannier, Scoville and Barvainis is assessed. The inclusion of additional states tends to decrease the maximum polarizations, though the calculated polarization is increased under conditions for which “superthermal” excitation occurs.
The Dao Radial Velocity Spectrometer and Recent Results
Authors: McClure Robert D. , Fletcher MJ.M. , Grundman W.A. , Richardson E.H.
Published: July 2016

A photoelectric radial-velocity spectrometer has been in use at the coudé focus of the 1.2m DAO telescope for several years. New improvements, resulting in a lowering of background noise, have allowed observations of stars significantly fainter than previously possible. Recent observations with the instrument at the coudé focus of the CFH telescope in Hawaii have shown that velocity measurements to better than 1 km s−1 accuracy are possible at 19th B magnitude. Various observing programs being carried out at DAO and CFHT are discussed.
Radial Velocities from CCD Detectors
Authors: Willmarth Daryl W. , Abt Helmut A.
Published: July 2016

The technique of measuring radial velocities by comparison of an object spectrum of unknown velocity to that of a template or mask spectrum of known velocity is well established. An analog device of this nature was developed by Griffin (1967), using a photomultiplier and mechanical mask to judge the degree of correlation between two spectra as a function of Doppler shift. This instrument was a large step forward in speed and efficiency, but suffered a low throughput due to a mask transmittance of about 10%.

Digital cross-correlation techniques soon evolved using either digitized data from photographic plates (Simkin 1974) or data obtained directly in digital form (Da Costa et al. 1977, Tonry and Davis 1979). These methods have the advantage of preserving the actual spectrum of the object from which other quantities can be derived. The Fourier methods used in these studies are also used to derive the Doppler broadening of the source.
Coravel Radial Velocities of Supergiants in the Small Magellanic Cloud
Authors: Maurice E. , Martin N. , Prévot L. , Rebeirot E.
Published: July 2016

Kinematical studies of the Magellanic Clouds began more than half a century ago, when Wilson, in 1918, first interpreted the gradient of the 17 radial velocities of gazeous nebulae in the Large Cloud in terms of rotation. In the case of the Small Magellanic Cloud, the first real attempt to understand the velocity field of this galaxy was performed by the Radcliffe astronomers (Feast et al., 1960, 1961). Their study was based on radial velocities of 40 stars and 13 HII regions.

With the installation by ESO of an objective-prisme astrograph in South Africa, in 1961, and then of several larger telescopes in Chile in 1968, the number of measurements significantly increased for Magellanic objects, in particular in the SMC. In this galaxy, the objective-prism observations resulted in about 100 stellar radial velocities (Florsch, 1972a) of probable members. A compilation by Maurice (1979) of all then known slit-spectrograph radial velocities gave velocities for 80 supergiants, 35 HII regions and 12 planetary nebulae.
Bibliography of Radial Velocity Papers (1981 – 1984)
Authors: Philip A.G. Davis
Published: July 2016

A Bibliography of Radial Velocity Papers has been constructed from two sources; volumes 30 -34 and 37 of Astronomy and Astrophysics abstracts (covering the second half of 1981 through the first half of 1984) and the papers in IAU Colloquium No. 88 (held in October 1984). All the papers listed under Radial Velocity in the index of Astronomy and Astrophysics abstracts were listed with the subject classification assigned by AAA. In some cases papers were assigned to two or more classifications and these papers are listed once each for each classification.

The bibliography is presented on pages 419 - 437 in the following format. The sheets presenting the information for each paper were too long to fit on one page in the book so each page has been broken up into three sections; А, B and C. Section A contains the abstract number, the names of the first three authors (and other authors if there are more than three) and the topic of the paper. Section B contains the title of the paper and repeats the abstract number. Section С contains the reference and repeats the abstract number. The entries are presented in groups of ten to aid the eye in following the entries across one page to another. There are seven sections to the Bibliography, I - VII.
Evolution of White Dwarfs: Starting from Planetary Nebulae
Authors: D’Antona Francesca
Published: July 2016

The ultimate aim in the study of White Dwarf (WD) evolution is to understand properly the observed Luminosity Function (LF) of WDs, that is the number of WDs observed per unit magnitude interval. The complicated route to the interpretation of this scarne quantity (12 fiducial points in the recent update of Liebert et al. 1988) is schematically summarized in figure 1. Clearly, the main input to the LF are the evolutionary (cooling) times, but it is necessary to consider their non trivial dependence on galactic evolutionary inputs, namely the initial mass function of disk stars, their age distribution with time (ultimately: the disk age), and their evolutionary properties. Stellar evolution enters in the problem of cooling by two main routes: first, by determining the mass of the WD as a function of the inital stellar mass and chemistry, second by fixing the internal constitution of the WD remnant for each given mass, and the initial physical conditions at the start of WD evolution (mainly the temperature distribution, which is important for the first phases of evolution). Of course, there is no need of good evolutionary inputs to study “theoretical” WDs. In fact, historically, the first approach in the study of “cooling” (Mestel 1952, Schwarzschild 1958)) has been directly related to the stimulating physical properties of these objects, in which neutrino losses at the beginning (Vila 1966, Savedoff et al. 1969) and, in late stages, liquification and crystallization of the plasma (Brush,Sahlin and Teller 1966, Hansen 1973) long recognized to be dominated by coulomb interactions, (Kirzhnits 1960, Abrikosov 1960, Salpeter 1961), are the main features to be investigated (Mestel and Ruderman 1967, Van Horn 1968, Kovetz and Shaviv 1970).
Equations of State of Hydrogen-Helium and Carbon-Oxygen Mixtures
Authors: Godon P. , Shaviv G. , Ashkenazi J. , Kovetz A.
Published: July 2016

The usual approach to the problem of the Equations Of State (EOS) for White Dwarfs and super giant Planets, under the conditions of high densities and low temperatures, faces two problems.

The first has to do with Pressure Ionization : the energy levels of the electrons in the case of extreme pressure ionization cannot be treated in the same way as the energy levels in a single isolated atom. The simple treatment of pressure ionization, in which the level of the continuum is reduced by an amount equal to the electrostatic energy, leads to problem because the number of energy levels, entering the Saha equation (partition functions), is not conserved, also the usual approach may lead to absurd results in which ions recombine as the density increases.
Gravitational Collapse of Mass-Accreting White Dwarfs
Authors: Isern J. , Canal R. , García D. , Hernanz M. , Labay J.
Published: July 2016

Massive star (M ≥ 10 M ) core collapse is the standard mechanism for neutron star formation (see Brown 1988 for a recent review). It has long been realized (see, for instance, van den Heuvel 1988, and references therein) that the neutron stars found in different types of binary systems cannot come from such a standard mechanism. Those systems include wide binary radio pulsars, millisecond pulsars (not in wide binaries), galactic bulge X–ray sources (including QPO’s), type I X–ray burst sources and X–ray transients, andγ–ray sources. Formation of those neutron stars is now widely attributed to the gravitational collapse of a white dwarf, growing above Chandrasekhar’s limit by mass accretion from the current neutron star’s companion in the binary system (Canal and Schatzman 1976; Canal and Isern 1979; Canal, Isern, and Labay 1980; Miyaji et al. 1980). Mass growth up to dynamical instability means that both explosive ejection of the accreted layers and explosive disruption of the whole star must be avoided. The former is associated with the nova phenomenon. The latter, with the occurrence of type I supernovae.
The CCD/Transit Instrument (CTI) Blue Object Survey
Authors: Kirkpatrick J. Davy , McGraw John T.
Published: July 2016

The CCD/Transit Instrument (CTI) is a 1.8 m, f/2.2 meridian-pointing telescope located on Kitt Peak. It has no moving parts, but utilizes two RCA charge-coupled devices (CCDs) aligned with columns in the east-west direction and operated in the “time-delay and integrate” (TDI) mode at the apparent sidereal rate to form an image of the sky as it transits (McGraw et al. 1986). The strip is 8.25 arcminutes wide north-south with length determined by the length of the night. Thus, each night the CTI surveys about 15 square degrees of the sky, or about 45 square degrees per year, to a nightly limiting magnitude of mv ≥ 20. One of the two CCDs in the focal plane always observes through a V filter while the other utilizes one of (U), B, R, or I, depending upon the sky brightness. These data are searched to find every detectable object and photometric parameters are calculated for each. These data become part of a Master List which contains the best estimate for each parameter and a History List which maintains a light curve for every detected object. The vital statistics of the project are listed in Table 1.
Diffusion and Metal Abundances in Hot White Dwarfs Gerard Vauclair
Authors: Vauclair Gérard
Published: July 2016

While the efficiency of gravitational settling to produce chemically pure atmospheres in white dwarf stars was outlined for the first time 30 years ago (Schatzman 1958), the competing role of the radiation flux in the hot white dwarfs was considered only 10 years ago (Fontaine and Michaud 1979; Vauclair, Vauclair and Greenstein 1979). At that time, there was more motivation to understand how metals could reappear in the long lived cool non DA white dwarfs, where diffusion time scales are shorter by orders of magnitude than evolutionary time scales. Various processes were invoked to help restore some metal content in the white dwarf atmospheres: convection mixing and dredge up, accretion of interstellar matter. In cool white dwarfs, the radiative acceleration is negligeable in the diffusion process; this is not the case at the hot end of the sequence where radiation may balance gravity. The short lived hot white dwarfs just started to become exciting with the contemporary discoveries that i) some show metallic lines in their spectra, both hydrogen rich and hydrogen poor; ii) some of these are pulsating. In the following years, the number of hot white dwarfs revealing trace abundance of metals has increased, mainly owing to IUE observations.
The Time Dependence of the Phases of the Harmonics Relative to the 1490 sec Fundamental in PG1346+082
Authors: Provencal J. L. , Clemens J. C. , Henry G. , Hine B. P. , Nather R. E. , Winget D. E. , Wood M. A. , Kepler S. O. , Vauclair G. , Chevreton M. , O’Donoghue D. , Warner B. , Grauer A. D. , Ferrario Lilia
Published: July 2016

White dwarf stars provide important boundary conditions for the understanding of stellar evolution. An adequate understanding of even these simple stars is impossible without detailed knowledge of their interiors. PG1346+082, an interacting binary white dwarf system, provides a unique opportunity to view the interior of one degenerate as it is brought to light in the accretion disk of the second star as the primary strips material from its less massive companion (see Wood et at. 1987).

PG1346+082 is a photometric variable with a four magnitude variation over a four to five day quasi-period. A fast Fourier transform (FFT) of the light curve shows a complex, time-dependent structure of harmonics. PG1346+082 exhibits flickering – the signature of mass transfer. The optical spectra of the system contain weak emission features during minimum and broad absorption at all other times. This could be attributed to pressure broadening in the atmosphere of a compact object, or to a combination of pressure broadening and doppler broadening in a disk surrounding the compact accretor. No hydrogen lines are observed and the spectra are dominated by neutral helium. The spectra also display variable asymmetric line profiles.
The Magnetic white dwarfs in AM Her variables
Authors: Wickramasinghe D.T.
Published: July 2016

There are now some 15 cataclysmic variables that have been recognised as being of the AM Her type. They are characterised by the presence of variable circular and linear polarisation in the optical and IR spectral regions, approaching 40% in some systems. The polarized radiation has been attributed to high harmonic cyclotron emission from hot (∼ 5 – 30 Kev) plasma located at accretion shocks near the poles of a highly magnetised (∼ 20 – 60 MG) white dwarf primary. There is hope that the study of the rich variety of phenomena exhibited by these systems will eventually enable us to probe the magnetic field structure of the underlying white dwarfs, perhaps even in more detail than has been possible with the isolated magnetic white dwarfs (Wickramasinghe (1987), Schmidt (1987)).
Synthetic Spectra of Magnetic White Dwarfs
Authors: Jordan Stefan
Published: July 2016

A new program for the calculation of theoretical spectra and wavelength dependend degrees of the linear and circular polarization for magnetic white dwarfs with hydrogen atmospheres has been developed. The main improvement compared to previous models is a more realistic treatment of the bound-free absorption and of the magnetooptical parameters arising from free electrons in the continuum. For the newly discovered magnetic white dwarf HS 1254+3430 a polar field strength of 18 MG was found. Calculations for the high field object Grw +70°8247 confirms the results of Wickramasinghe and Ferrario (320 MG) but gave a better fit to the spectrum at wavelengths larger than 6200 Å.
The Period Problem of the Interacting Binary White Dwarf System AM CVn
Authors: Solheim J.-E.
Published: July 2016

A short review is given of the searches for an orbital period of this (believed to be) interacting binary white dwarf system. Today, 3 or 4 periods are known. A polar ring accretion model is proposed to explain the observations – at least partly.
On the Separations of Common Proper Motion Binaries Containing White Dwarfs
Authors: Oswalt T.D. , Sion E.M.
Published: July 2016

Luyten [1,2] and Giclas et al. [3,4] list over 500 known common proper motion binaries (CPMBs) which, on the basis of proper motion and estimated colors, are expected to contain at least one white dwarf (WD) component, usually paired with a late type main sequence (MS) star. Preliminary assessments of the CPMBs suggest that nearly all are physical pairs [5,6]. In this paper we address the issue of whether significant orbital expansion has occurred as a consequence of the post-MS mass loss expected to accompany the formation of the WDs in CPMBs.

Though the CPMB sample remains largely unobserved, a spectroscopic survey of over three dozen CPMBs by Oswalt [5] found that nearly all faint components of Luyten and Giclas color class “a-f” and “+1”, respectively, or bluer were a WD. This tendency was also evident in a smaller sample studied by Greenstein [7]. Conversely, nearly all CPMBs having two components of color class “g-k” and “+3” or redder were MS+MS pairs. With the caveat that such criteria discriminate against CPMBs containing cool (but rare) WDs, they nonetheless provide a crude means of obtaining statistically significant samples for the comparison of orbital separations: 209 highly probable WD+MS pairs and 109 MS+MS pairs.
Structure and Evolution of SV Centauri
Authors: Drechsel H. , Rahe J. , Wargau W. , Wolf B.
Published: July 2016

Optical photometric and spectroscopic observations of the eclipsing binary SV Cen were used to derive orbital elements and absolute dimensions of the peculiar early-type contact system. UV spectroscopic observations obtained with the IUE satellite yielded the detection of mass loss from the system forming an expanding circumbinary envelope. SV Cen exhibits a non-uniform rate of period decrease, with major variations on a time scale of a few years. The period changes are explained in terms of loss of angular momentum carried away by the ejected matter. Short-term fluctuations of the stellar wind on a time scale of a few hours were found from an analysis of the envelope line profiles of UV resonance lines. A model of the system is derived, and the evolutionary stage and interaction processes are discussed.
The Time Change of the AW UMa System
Authors: Kurpińska M. , Otmianowska K.
Published: July 2016

In connection with the period change of the AW UMa system, an A-type contact binary, as it was indicated by Woodward (1980) and elaborated by Kurpifiska (1980), we try to analyse with the Wilson-Devinney code all accessible light curves of this star before and after the observed shortening of the period.
The Minimum Orbital Period of Hydrogen-Rich Cataclysmic Binaries
Authors: Sienkiewicz R. , Paczyński B.
Published: July 2016

This communication summarizes the investigations of the relationship between the minimum binary period and the evolution of very short period hydrogen-rich cataclysmic binaries /CB's/.
In the first work /Paczyński, 1981/ some ideas were developed concerning an influence of gravitational radiation on the evolution of CB's, and some quantitative predictions
were done. In the next paper /Paczyński and Sienkiewicz, 1981, hereafter referred to as PS/ more detailed numerical calculations were performed. We considered a widely accepted picture
of such binaries. They are believed to have a white dwarf primary component surrounded with an accretion disk. The secondary component, probably the lower main sequence star or degenerate dwarf, overflows its Roche lobe, and matter flows from the inner Lagrangian point towards the disk. In all known cases but one, the binary orbits are circular. No hydrogen-rich CB's are observed with periods below 80 minutes. Because the nuclear evolution cannot be of any importance for the secondary, we assumed that angular momentum loss due to gravitational radiation is the driving force which causes the mass transfer and a cataclysmic activity.
We followed the evolution of such system with a very simple and fast code, and the best input physics actually available /PS, Sienkiewicz, 1981/. We have calculated a large number
of evolutionary tracks for many values of a total mass of a binary and the initial mass of the secondary.
An Optical Burst in Sco X-1
Authors: Mauder H.
Published: July 2016

Sco X-1 is known to show periods of correlated X-ray and optical activity on a timescale of minutes to days, see e.g. Ilovaisky et al.,1980. The rapid optical variations show typically an amplitude of about 5%. During the 1979 campaign on Sco X-1, blue band observations were obtained on several nights with the ESO 1 m photometric telescope with a time resolution of 2 seconds.
Saturn’s E ring
Authors: Baum W.A. , Kreidl T.J. , Wasserman L.H.
Published: July 2016

The spatial distribution of material in Saturn’s E ring has been derived from ground-based CCD observations obtained at the time of the 1980 edge-on presentation. The ring commences abruptly near 3 RS, peaks at the orbit of Enceladus (3.94 RS), and has tenuous outskirts to more than 8 Rs. On reasonable assumptions, we calculate the attenuation factor to be 5xl0-11km-1in the equatorial plane near Enceladus, and the physical thickness of the ring there to be 7500 km (FWHM). The attenuation factor in the equatorial plane is lower by a factor of 8 at Tethys, 76 at Dione, and roughly 1000 at Rhea, while the physical thickness increases by factors of 1.7, 2.9, and 5.5, respectively. This distribution of ring material appears to call for interactions with charged particles and fields. If the E-ring particles are predominantly icy and small, the total mass of the ring is probably less than 106tons.
Unusual imaging observations of Saturn's rings
Authors: Terrile Richard J.
Published: July 2016

Voyager cameras recorded a number of surprising and unusual features in Saturn's rings. These features include the large-scale markings (commonly called spokes) seen rotating around Saturn in the B-Ring, kinks and clumps in the F-Ring and A-Ring gap (Keeler or Encke gap) ringlets, wavy gap edges in the Cassini and A-Ring gaps, eccentric ringlets and chaotic ringlet structures. Detailed observations of these features by the Voyager imaging experiment will be discussed.
Structure of Saturn's rings from Voyager radio occultation measurements
Authors: Tyler G.L. , Marouf E.A. , Eshleman V.R.
Published: July 2016

Radio occultation observations of Saturn's rings with Voyager 1 provided measurements of the collective microwave opacity and the near-forward scattering characteristics of the ring particles at 3.6 and 13 cm wavelengths. These measurements were obtained at a ring opening of 6.1°. Experimentally, the three classical rings and the Cassini division comprise four distinct structural regimes whose characteristics are as follows: Ring C exhibits a background of gently undulating (~ 1000 km radial scale) structure of normal opacity τ(3.6cm) ≲0.25, [τ = sin(6.1 °)1 n(I/Io)], imbedded in which are several narrow ringlets of less than few hundred km in width and of microwave opacity in the range 0.5 to 1.0. The opacity ratio ρ = τ(3.6cm)/τ(13cm) falls in the range 1.4 to 1.6 for most of ring C, indicating that a substantial fraction of the crosssectional area is due to particles in the 1 to 4 cm diameter range. Three gaps are clearly evident in ring C, two of them encompass imbedded ringlets of extremely sharp edges. The dual-wavelength opacity of several imbedded ringlets is consistent with models in which particles smaller than a few centimeters pile-up near the edges. In the Cassini division, several gaps of extremely sharp edges separate regions of opacity in the range 0.08 to 0.25; the opacity is nearly independent of the wavelength, precluding the existance of a substantial fraction of particles less than about 4 cm in size.
Voyager planetary radio astronomy: Grain and particle impacts shot noise in Saturn's ring plane
Authors: Aubier M.G. , Meyer-Vernet N. , Pedersen B.M.
Published: July 2016

Radio emissions were observed by Voyager 1 and Voyager 2 planetary radio astronomy experiments during saturnian ring plane crossings. Several mechanisms are proposed and tested. Quasi-thermal noise is negligible. Shot noise due to electrons and ions collected and/or emitted by antennas and spacecraft can explain not too intense noise. However, for the strong noise in the ring plane, observed by Voyager 2 at ~ 2.9 Rs, we must take into account shot noise due to grain impacts. A quantitative evaluation of this process gives an estimation of the dust size ~ 1.1 µm close to the G ring.
On the radial structure of planetary rings
Authors: Harris A.W. , Ward W.R.
Published: July 2016

A ring of particles in orbit about a planet experiences a viscous shear stress due to the radial gradient of orbital velocity. This stress tends to spread the ring with time. At low optical depth (τ ≲ 0.5), and again at high optical depth (τ ≳ 2), the shear stress is an increasing function of optical depth. In the intermediate range (0.5 ≲ x ≲ 2), stress may decrease with increasing τ, leading to a diffusive instability which will tend to break an Initially uniform ring into ringlets of high and low optical depths.
Dense but «collisionless» orbiting rings
Authors: Michel F.C.
Published: July 2016

The discovery by Voyager, that the rings of Saturn are substructured into a multitude of narrow ringlets, has posed some severe theoretical difficulties. These rings have substantial optical depths, implying high collision rates and therefore rapid diffusive spreading, which would lead to the ringlet structure being eradicated.

Suggestions have been forwarded that this substructure is either a) dynamically maintained by many small perturbing subsatellites or b) is not actually in the form of closed rings but is a spiral pattern of density waves. Voyager II was unable to detect such subsatellites, and many of the broader isolated ringlets (albeit not necessarily the finest features at the few kilometer scale) are clearly observed to be closed rings, rather than segments of a spiral.

We propose that convective motion, a helical rolling motion of a ringlet as it orbits, provides a stabilizing influence. For ringlets of negligible mass orbiting a point mass, the ringlets can be arbitrarily dense without collisions acting to dissipate them. For the realistic case of an oblate planet and finite ring mass, a small but finite collision rate (or other compensating perturbations) are required. Convective motions then serve to vastly reduce the effective viscosity within a ringlet and thereby greatly increase its evolutionary lifetime.
Objectives of U.V. observations in the study of the Saturnian rings
Authors: Bruston P.
Published: July 2016

Within the last few years increasing interest has been expressed concerning U.V. and far U.V. observations within the Solar System from Earth orbit (see e.g. (1), (2)). In France, a wide community of scientists and institutes working in the field of planetary science has proposed such a mission, SOLSTIS (3), which combines imaging capability with high spectral and spatial resolutions.
Supernova Remnants and their Supernovae
Authors: Kirshner Robert P.
Published: July 2016

Observing supernova remnants provides important clues to the nature of supernova explosions. Conversely, the late stages of stellar evolution and the mechanism of supernova explosions affect supernova remnants through circumstellar matter, stellar remnants, and nucleosynthesis. The elements of supernova classification and the connection between supernova type and remnant properties are explored. A special emphasis is placed on SN 1987a which provides a unique opportunity to learn the connection between the star that exploded (whose name we know) and the remnant that will develop in our lifetimes.
The Early Evolution of Supernova Remnants
Authors: Chevalier R.A.
Published: July 2016

The density distribution of the supernova ejecta and that of the surrounding medium are the most important parameters for the early evolution of supernova remnants. The distribution of the ejecta depends on the detailed hydrodynamics of the explosion, but the outer parts of a supernova can probably be represented by a steep power law density distribution with radius. Self-similar solutions are especially useful for modeling the interaction of a supernova with its surrounding. The supernova first interacts with mass loss from the progenitor star. Evidence for circumstellar interaction is present in a number of extragalactic supernovae, including SN1987a. The explosions of massive stars probably interact with circumstellar gas for a considerable time while Type Ia supernovae interact more directly with the interstellar medium. X-ray spectroscopy is a good diagnostic for the physical conditions in young supernova remnants and for the composition of the supernova gas.
Exosat Observations of Young SNRs
Authors: Smith A.
Published: July 2016

In this work we study the 2 – 10 keV spectra of eight relatively well known SNRs. These spectra were obtained with the medium energy experiment on-board the X-ray satellite EXOSAT. Details of the EXOSAT mission can be found in Taylor et al 1981 and the ME experiment is described in Turner, Smith and Zimmerman 1981. The ME experiment is well suited for this study since it provides a high sensitivity and a narrow field of view (45 ' FWHM). These spectra are considered in the context of a model in which the 2–10 keV continuum arises from shock heated interstellar material.
Einstein Bragg Crystal Spectrometer Observations of Cas A – A Nonequilibrium Ionization Interpretation
Authors: Markert T.H. , Blizzard P.L. , Canizares C.R. , Hughes J.P.
Published: July 2016

We use Einstein FPCS observations of lines of highly ionized neon, silicon and sulfur to constrain the parameters of the supernova remnant Cas A.
Line Emission Processes in Atomic and Molecular Shocks
Authors: Shull J. Michael
Published: July 2016

This review discusses the observations and theoretical models of interstellar shock waves in diffuse and molecular clouds. After summarizing the relevant gas dynamics, atomic, molecular and grain processes, and physics of radiative and magnetic precursors, I describe observational diagnostics of shocks. I conclude with a discussion of two new topics: unstable or non-steady shocks and thermal conduction in metal-rich shocks.
Radio Studies of Supernova Remnants: Patterns and Statistics
Authors: Caswell J.L.
Published: July 2016

Most supernova remnants (SNRs) in our galaxy have been discovered from their radio emission and for the majority this remains the only means of studying them. In this review the impact of new radio observations is discussed.

The increased detail of recent radio maps reveals some common patterns among SNRs, despite their generally diverse appearance. The patterns can give us clues to both the intrinsic properties of the supernova and the influence of the interstellar medium. With a fuller understanding of individual remnants, there are better prospects for meaningful interpretation of statistical studies.
An Infrared Survey of Galactic Supernova Remnants
Authors: Arendt Richard G.
Published: July 2016

Presented here are preliminary results from a survey of supernova remnants (SNRs) in the data base collected by the Infrared Astronomical Satellite (IRAS). About one-third of the known galactic SNRs are visible in the IRAS data. Confusion with other sources in the galactic plane prohibits the detection of many remnants. The objects that are detected have similar spectral characteristics and temperatures, except that the three youngest remnants known, Tycho, Kepler, and Cassiopeia A, are distinctly warmer.
Analysis of Multiwavelength Observations of IC443
Authors: McColloug M.L. , Mufson S.L.
Published: July 2016

High resolution observations at radio, infrared, optical and X-ray wavelengths have been made (Mufson et al. 1986). The infrared spectrum determined from the IRAS observations has been fitted with models which include shock heated dust, infrared line emission, and radiatively heated dust emission. Numerical simulations of a supernova expanding into a uniform medium, which describe the X-ray and large scale radio emission, are presented.
The Frequency of Supernovae in External Galaxies
Authors: Cappellaro E. , Turatto M.
Published: July 2016

A new determination of the SN-frequency in different morphological types of galaxies, obtained from the material of the Asiago SN-Search, is presented. From these values we derive a mean interval between SN events in our Galaxy consistent with values determined in different ways.
The Environments of Cool Stars
Authors: Stencel Robert E.
Published: July 2016

This review describes recent conclusions about the physical environment of red giant and supergiant stars. This includes coronae, chromospheres, dust formation and stellar winds. This knowledge can provide the boundary conditions for considering what role such objects play as members of binary star systems, where tidal forces and companion behavior alter observed characteristics.
The Radio Properties of Symbiotic Stars
Authors: Seaquist E.R.
Published: July 2016

Radio thermal bremsstrahlung emission has now been detected at centimeter wavelengths from about thirty symbiotic stars. These data combined with optical and IR data show that the radio emission in most systems may be understood in terms of the ionization of part of the wind of a red giant by a hot companion. The radio properties of symbiotic stars are reviewed and the agreement with and the limitations of this picture are examined.
Accretion from Stellar Winds
Authors: Livio Mario
Published: July 2016

Recent calculations have demonstrated that accretion from a stellar wind is very probably unsteady. The average rate of accretion of angular momentum is lower by about a factor 5 than the rate at which angular momentum is deposited into the Bondi-Hoyle accretion cylinder. This makes disk formation from wind accretion very difficult, in particular in the case of massive x-ray binaries. A combination of x-ray, uv and optical observations of symbiotic and related systems, as well as spin-up information on x-ray binaries, can be used to determine whether an accretion disk does form. Such observations can provide us with valuable information on the process of accretion from an inhomogeneous medium.
Spectral Variations of AG Dra Between 1981 and 1985
Authors: Huang C.C. , Chen Y.F. , Chen L.
Published: July 2016

After a long quiet phase AG Dra underwent an outstandingly active phase with two outbursts in 1980 Nov. and 1981 Nov.(Viotti et al, 1984). Since then a new quiet phase has followed. In this work we analyse two spectra of AG Dra, of which, one was taken in 1981 by C.C. Huang at the Haute-Provence Observatory using the Marly spectrograph with a dispersion of 80 A/mm at the 1.2 m telescope, the other was obtained by Dr Y.Andrillat in 1985 with the same instrument.

Figure 1 shows the spectral variations of AG Dra between 1981 and 1985. The main features of the emission line spectrum are not much different between the two spectra, except that in 1985 there was a new wide weak emission line at 3488 A possibly due to FeII. There were a lot of strong emission lines due to H, HeI, HeII and 0III in both spectra. The spectrum of the late-type component was much more obvious in 1985 than in 1981. In 1985 the lines of CaII K, CaIλ4227 and the G-band of CH were quite strong. In addition we measured a lot of absorption lines due to FeI, SrII and TiII on the 1985 plate. The Balmer continuum emission and the blue contiuum were enhanced in 1981. On the 1981 plate the stellar spectrum in ultraviolet can be traced beyond 3200 A and the blue continuum heavily veiled the spectrum of the cool component. In 1985 they were much weaker.
Science and the Wonders of Creation
Authors: His Holiness Pope Paul VI
Published: July 2016

We welcome today with special joy the presence among us of scholars who have come from all parts of the world to our small State of Vatican City, to study the Spectral Classification of the Stars. We know that, in the spirit of collaboration, you will confer together on the topics proposed by the International Astronomical Union. We thank you for the honour of your presence and we are glad of this opportunity to show our continued interest in Science and particularly in Astronomy; this interest leads us to maintain the Vatican Observatory and to support our esteemed Academy of Sciences.
Future Objective-Prism Spectral classification at MK Dispersion
Authors: Houk Nancy
Published: July 2016

A brief review and summary of results from Volumes 1 (-90° to -53°) and 2 (-53° to -40°) of the University of Michigan Catalogue of Two-Dimensional Spectral Types for the HP Stars is given. Plans for the classification of the remaining southern HD stars are outlined. Future plans for observation and classification of northern stars are discussed, including the problem of whether to limit such classification to the HD stars. More general remarks about spectral classification in the future, especially for fainter stars, conclude the paper.
A Study of Main Sequence Early Type Stars
Authors: Sinnerstad Ulf
Published: July 2016

A spectroscopic and photometric study of 75 normal main sequence B2-B6 stars has been carried out. From the spectra (12 Å/mm, 3700-4800 Å) are determined: equivalent widths of all measurable lines, line profiles of hydrogen lines and v sin i. The photometric work includes besides uvby and β photometry, also photoelectrically determined line strengths of Hα and He I 4471 Å. Some preliminary results concerning the relation between the MK types and the atmospheric fundamental parameters (Teff, log g) of the stars are briefly discussed.
Comparisons of Temperature Classes Obtained by Spectroscopic and Photometric Techniques: M-Type Dwarfs, Giants, and Supergiants
Authors: Wing R. F. , Yorka S. B.
Published: July 2016

Temperature classes based on photometric measurements of the 7100 Å band of TiO are compared with published spectroscopic classifications by various investigators. Dwarfs, giants, and supergiants are treated separately. The photometric types are in excellent agreement with types given by P. C. Boeshaar for M dwarfs and by P. C. Keenan and Y. Yamashita for M giants. In all other cases the scatter is larger. The usefulness of the types given by various authors for dwarfs and giants is tested by examining their correlation with color temperature determined by narrow-band photometry.