bluuebunny/crossref_metadata_2025 huggingface dataset:
The E-ring: interactions with plasma and implications for its evolution
Authors: Johnson T.V. , Morfill G.E. , Grun E.
Published: July 2016

A number of lines of evidence suggest that the particles making up the E-ring are small, on the order of a few microns or less in size (Terrile and Tokunaga, 1980, BAAS; Pang et al., 1982 Saturn meeting; Tucson, AZ). This suggests that a variety of electromagnetic and plasma affects may be important in considering the history of such particles. We have shown (Morfill et al., 1982, J. Geophys. Res., in press) that plasma drags forces from the corotating plasma will rapidly evolve E-ring particle orbits to increasing distance from Saturn until a point is reached where radiation drag forces acting to decrease orbital radius balance this outward acceleration. This occurs at approximately Rhea's orbit, although the exact value is subject to many uncertainties. The time scale for plasma drag to move particles from Enceladus' orbit to the outer E-ring is ~104yr. A variety of effects also act to remove particles, primarily sputtering by both high energy charged particles (Cheng et al., 1982, J. Geophys. Res., in press) and corotating plasma (Morfill et al., 1982). The time scale for sputtering away one micron particles is also short, 102 - 10 yrs. Thus the detailed particle density profile in the E-ring is set by a competition between orbit evolution and particle removal. The high density region near Enceladus' orbit may result from the sputtering yeild of corotating ions being less than unity at this radius (e.g. Eviatar et al., 1982, Saturn meeting). In any case, an active source of E-ring material is required if the feature is not very ephemeral - Enceladus itself, with its geologically recent surface, appears still to be the best candidate for the ultimate source of E-ring material.
On the electric charge carried by dust grains excitation of violent discharge
Authors: Lafon Jean-Pierre J. , Millet Jean M.
Published: July 2016

Field emission can, when excited by electric influence, destabilize the equilibrium charge carried by bodies in space plasmas and trigger violent discharge.
Statistical theory of the planet growth
Authors: Hornung P. , Pellat R.
Published: July 2016

We compute analytically the main average parameters ½, ½= β½necessary for understanding the planet growth. We take into account simultaneously the inelastic hard sphere collisions (including gravitational focusing) and the long distance self gravitational interaction between the planetesimals orbiting around the Sun.
On the heterogeneous appearance of Saturn's rings at high optical resolution
Authors: Cook A.F. , Franklin F.A. , Shoemaker E.M. , Terrile R.J.
Published: July 2016

Shoemaker and Terrile have shown that several small satellites can be the parents of Saturn's rings and have suggested these as the origin of the broad systematic differences in the photometric properties of the rings. Dramatic variations on the smallest scales appear in the images obtained from Voyager. The variations of the surface of Enceladus suggest the importance of differentiation of satellites heated by tidal action maintained by resonances, as pointed out by C.M. Yoder. Subsequent break-up of such satellites, either under a large impact or under increasing tidal action of Saturn as its mass increased, would have yielded a mixture of different crustal and interior materials with different spectra of sizes and masses. We shall discuss the possible role of radial differentiation of particles in terms of their masses initiated by the combined activity of instabilities discussed long ago by Maxwell and by Cook and Franklin with those proposed recently by Ward and by Lin and Bodenheimer. In this way, we may reach an explanation of variations on the smallest scales. Comparison will be made with the expected behaviour of a primary accretion disk composed of a uniform distribution of material.
Resonance structure in the early evolution of the Saturn system and the location of the inner satellites
Authors: Torbett M. , Smoluchowski R.
Published: July 2016

While the ring system ot Saturn may be the last vestige of accretion around the embryo which eventually became Saturn, the satellites accreted from the planetesimal swarm. If Titan reached a significant fraction of its present mass early in the evolution, then this massive satellite may have influenced the growth of the rest of the planetesimals through its major commensurability resonances. The accretional growth of an object within the swarm is proportional to the rate of encounters of other objects. At the principal (2:1, 5:2, 3:1) resonances the eccentricities of planetesimals are increased by the gravitational perturbation by Titan and the greater radial excursions induced thereby serve to enlarge the “feeding zone” of large objects (1). In between the resonances gas drag will tend to dampen eccentricities. Hence the mean value of eccentricity at,the resonances will be markedly enhanced above that of the background planetesimal swarm which would lead to accelerated growth of satellite embryos at these locations. If this is the case, then why is the Saturnian satellite system not in a resonant configuration today? The answer is that while the disk is present the locations of the resonances are different from where they would be in the absence of the disk. Thus, during the evolution of the system when the disk is gradually accreted by the central object to become Saturn, the original resonant structure is destroyed and the satellite embryos move out of resonance with Titan.
Rendez vous with Saturn's rings
Authors: Nock Kerry T.
Published: July 2016

A mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.
Concluding remarks on the planetary rings conference
Authors: Stone E.C.
Published: July 2016

In the past five years ring systems have been discovered around Uranus and Jupiter and a wealth of new data acquired about Saturn’s rings. This vigorous observational program has been accompanied by renewed theoretical interest in ring systems. Although all of these topics have been addressed in papers at this first conference on planetary rings, these concluding remarks are focused on some of the key aspects of Saturn’s rings about which more needs to be understood through further data analysis, calculations, and observations.
The Circumstellar Structure Around Supernovae
Authors: Lundqvist P. , Fransson C.
Published: July 2016

The time dependent ionization and temperature structure of the circumstellar medium around supernovae has been calculated, in order to interpret recent supernova radio observations. For a stellar wind origin of the circumstellar medium, we relate the time of radio turn-on to the progenitor mass loss rate. We also show that large column densities for the UV resonance lines are expected. The results are applied to SN 1979c, SN 1980k and SN 1987A.
Analysis of the Spectrum of the Type V Supernova SN1986J
Authors: Hamilton A.J.S. , Vacca W.D. , Pradhan A.K. , Rupen M. P. , Gunn J. E. , Schneider D. P.
Published: July 2016

The supernova SN1986j resembles the prototypical Type V supernova SN1961v in the relatively slow ∼1000km/s expansion velocity, the slow light curve, and also in the Hα dominated spectrum. The optical spectrum is similar to the spectra of some novae, and some OB stars with massive winds, being characteristic of a nebular plasma at about 1010cm−3 and 104K. What makes SN1986j exceptional is its tremendous radio luminosity, the brightest radio supernova observed to date. The radio emission indicates the presence of a massive circumstellar wind, with which the SN ejecta are now colliding. Since the cooling time of the optically emitting gas is about an hour, a heat source is required to power the light curve. Shocks moving back into the ejecta offer a natural heat source, and account quantitatively for the observed luminosity and spectral character of SN1986j. The large Hα/Hβ ratio is attributed to trapping of Ly α, which pumps the n = 2 level of hydrogen, causing a finite optical depth in Balmer lines, and converting Hβ to Pα and Hα. The ratio of the derived H(n = 2) density and column density yields a size for the Hα emitting region consistent with the thickness of a cooling shock, but less than 10−7 of the 1017cm VLBI size. An important discriminant between shock models and photoionization models of the spectrum is that shocks predict Lyman 2-photon emission. The mass of the optically emitting material in SN1986j is about 1M⊙, substantially less than the 2000 M⊙ argued in the case of SN1961v by Utrobin. However, there may be, and probably is, considerably more unobserved ejecta. This material should reveal itself as the remnant of SN1986j continues to evolve.
Nova GK Persei – A Miniature Supernova Remnant?
Authors: Seaquist E.R. , Frail D.A. , Bode M.F. , Roberts J.A. , Whittet D.C.B. , Evans A. , Albinson J.S.
Published: July 2016

We present radio and optical images of the shell-like remnant of the 1901 outburst of Nova GK Persei. The behaviour of this object is remarkably similar to supernova remnants. The synchrotron radiation-emitting shell is polarized with the magnetic field oriented radially, as in young SNR’s. This similarity plus extensive data we have acquired on the expansion and the interstellar environment of GK Per indicate that the nova shell is colliding with ambient gas whose density is substantially higher than the ISM.

Furthermore, there is strong evidence that the ambient gas is circumstellar rather than interstellar, and that this material is the shell of an ancient planetary nebula associated with the white dwarf companion of GK Per.
Kinematics of Oxygen-Rich Filaments in Puppis A
Authors: Winkler P. Frank , Tuttle John H. , Kirshner Robert P. , Irwin Michael J.
Published: July 2016

We have measured proper motions for fast, oxygen-rich knots in Puppis A, which we demonstrate are probably uncontaminated ejecta from the progenitor star’s core. Typical fast knots show motions of 0.1-0.2 arcsec yr-1 diverging from a point 4’ northeast of the center of the radio shell. A model assuming constant expansion fits the data well and gives an age of 3700 ± 300 yr for Puppis A. We also present new spectra which indicate the presence of neon along with oxygen in the fast knots.
The Oxygen-Rich Supernova Remnant in the Small Magellanic Cloud
Authors: Blair William P. , Raymond John C. , Danziger John , Matteucci Francesca
Published: July 2016

We report ultraviolet and optical spectra of IE 0102-7219, the oxygen-rich supernova remnant in the Small Magellanic Cloud. The UV data contain strong lines of oxygen, carbon, neon, and magnesium. OI recombination lines in the optical and UV permit the relative line intensities to be determined from 1200Å to 1 micron. Models assuming shock excitation and X-ray photoionization have been calculated and compared with the observations.
New Supernova Remnants in M33
Authors: Long Knox S. , Blair William P. , Kirshner Robert P. , Winkler P. Frank
Published: July 2016

Existing catalogues of supernova remnants (SNRs) in external galaxies are very incomplete. Potentially however, such samples are of great importance in understanding SNRs, since the distances to objects in a given sample are essentially the same and since absorption is small (compared to galactic SNRs). We have recently obtained Hα+[NII], Hβ, [SII], [OIII], and 6100 Å continuum CCD images of nine selected areas in M33 using the KPNO 4m. In addition to the six SNRs already known to exist in the fields we have surveyed, we have identified 21 other nebulae with [SII]:Hα+[NII] ratios which may be SNRs. Spectra of seven of these nebulae were obtained subsequently and show that the majority are indeed SNRs. A more detailed analysis of regions containing significant HII region contamination and a search for very small diameter remnants is currently underway.
Supernova Remnant Shocks in an Inhomogeneous Interstellar Medium
Authors: McKee Christopher F.
Published: July 2016

The inhomogeneity of the interstellar medium (ISM) has a profound effect on the propagation of the interstellar shock generated by a supernova and on the appearance of the resulting supernova remnant (SNR). Low mass supernovae produce remnants that interact with the “pristine” ISM, which has density inhomogeneities (clouds) on a wide range of scales. The shock compresses and accelerates the clouds it encounters; inside the blast wave, the clouds are hydrodynamically unstable, and mass is injected from the clouds into the intercloud medium. Embedded clouds interact thermally with the shock also, adding mass to the hot intercloud medium via thermal evaporation or subtracting it via condensation and thermal instability. Mass injection into the hot intercloud medium, whether dynamical or thermal, leads to infrared emission as dust mixes with the hot gas and is thermally sputtered. The remnants of massive supernovae interact primarily with circumstellar matter and with interstellar material which has been processed by the ionizing radiation and wind of the progenitor star. After passing through any circumstellar material which may be present, the shock encounters a cavity which tends to “muffle” the SNR. The remnants of massive supernovae therefore tell us more about the late stages of the evolution of massive stars than about the ISM.
Collective Effects in Shock Propagation Through a Clumpy Medium
Authors: Norman M.L. , Dickel J.R. , Livio M. , Chu Y.-H.
Published: July 2016

A numerical simulation of shock propagation in a clumpy medium with a weak magnetic field is presented which illustrates a number of dynamical processes of potential importance for explaining spectral line width and radio polarization measurements in supernova remnants.
Radio Continuum Observations of Supernova Remnants at 22 GHz
Authors: Tateyama C.E. , Sabalisck N.S.P. , Abraham Z.
Published: July 2016

We describe in this work the results of high frequency radio continuum observations of 96 supernova remnants (SNRs) obtained at the Itapetinga Observatory at 22 GHz. We have detected 15 SNRs. Most of the strongest SNRs detected were previously classified in terms of their spectral and morphological properties as filled-center type (Crab-like). Some of the others have doubtful classifications.
Shock Waves, Particle Acceleration and Non-Thermal Emission
Authors: Blandford R.D.
Published: July 2016

Some recent developments in the theory of particle acceleration at supernova shock fronts are reviewed and the confrontation of this theory with measurements of galactic cosmic rays and observations of supernova remnants is discussed. Supernova shock waves are able to account for the energetics, spectrum and composition of galactic cosmic rays, though it remains difficult to understand acceleration of ∼ 105 GeV particles. Recent developments in the analysis of interplanetary shock waves and in the numerical simulation of quasi-parallel shocks are encouraging. Interpretations of different categories of remnants are reviewed and a speculative interpretation of the optical companion to SN1987a is discussed.
Possibilities for Observations with the Infrared Space Observatory of Emission from Shock–Heated Dust in SNRs
Authors: Svestka J.
Published: July 2016

The possibilities for observing infrared emission from shock-heated dust in SNRs with the future Infrared Space Observatory (ISO) are illustrated with calculations of the ISOPHOT-P and ISOPHOT-C flux densities and integration times for radiation from six selected SNRs in eight wavelength bands between 4µm and 180µm.
Fabry-Perot Observations of [FeX] in the Cygnus Loop and IC443
Authors: Ballet J. , Caplan J. , Rothenflug R. , Soutoul A.
Published: July 2016

We present the first results of an observational program of SNRs in the coronal lines of [FeX] and [FeXIV] using the Fabry-Perot spectrophotometer of the Observatoire de Marseille. These support previously published brightnesses.
The Evolution of Older Remnants
Authors: Fall S.A.E.G.
Published: July 2016

An older remnant will be defined as one in which radiative cooling occurs somewhere and has swept up enough mass for the details of the explosion to be less important than the state of the interstellar medium in which the explosion occurred. Without discussing any particular remnant in detail, I will consider how large and small scale density variations in the ambient medium affect the appearance and energetics of such remnants. Finally I will show that radiative instabilities can modify the emission spectrum of radiative shocks in such a way that a naive interpretation of these spectra can be very misleading.
Numerical Models of Supershell Dynamics
Authors: Mac Low Mordecai-Mark , Norman Michael L. , McCray Richard A.
Published: July 2016

Superbubbles play an important role in determining the state of the ISM in both spiral and irregular galaxies. We are modeling supershell dynamics in both homogeneous and stratified atmospheres using ZEUS, a 2-D hydrocode. We find that when a superbubble blows out of a Gaussian atmosphere, the cold, dense shell is not greatly accelerated. In addition, we believe that we observe the Vishniac overstability in radiative, decelerating shells.
A Nonthermal Superbubble in the Irregular Galaxy IC 10
Authors: Skillman Evan D.
Published: July 2016

New high resolution radio continuum images of the nearby irregular galaxy IC 10 have revealed a large (> 250 pc) nonthermal source. The source is roughly circular with a spectral index of ∼ –0.5, and is most likely a very large supernova remnant. Its large size suggests that it is the result of several supernovae, and may be related to the supershells observed in our own and other galaxies.
Supernovae Blast Waves in Proto-Dwarf Galaxies
Authors: Noriego-Crespo Alberto , Bodenheimer Peter
Published: July 2016

Gas mass loss in proto-dwarf galaxies can be efficiently driven out by blast waves created by the first generation of supernovae. There is, however, a threshold set by the total gravitational potential beyond which gas mass loss does not occur. This limit is in agreement with the one predicted by some Cold Dark Matter senarios.
Highlights of I.A.U. Colloquium 101: Excerpts from a Panel Discussion
Authors: van den Bergh Sidney , Wheeler Craig , Fesen Rob , Strom Richard , Helfand David , Heiles Carl
Published: July 2016

Editors’ Note

At the conclusion of IAU Colloquium 101 a panel discussion was held. The panellists were asked to give their opinions on significant new developments presented at the Colloquium and to outline questions to be answered in the future. The editors have summarized the discussion.
Orbital Parameters of Three Symbiotic Stars
Authors: Leibowitz Elia M , Formiggini Liliana
Published: July 2016

The optical light curves of the three symbiotic stars AG Dra, AX Per and AG Peg, in the U, B and V photometric bands, in the quiescent states of these stars, are interpreted on the basis of a “reflection” model for the observed light variations. A least squares fit of a numerical model that is constructed to the observed magnitudes of the stars yields the value of few of the orbital elements of these binary systems. Some predictions are made on the basis of the model and its parameter values about the detailed structure of the light curves of the three stars, and of the expected structure of radial velocity curves of the cool components in these systems.
Dust Emission from Symbiotic Stars: Interpretation of IRAS Observations
Authors: Anandarao B.G. , Taylor A.R. , Pottasch S.R.
Published: July 2016

Symbiotic stars are strongly believed to be binary systems - a hot component presumably a white dwarf ionizing and exciting gas from a cool primary star undergoing mass-loss. Silicate dust temperatures for six symbiotic stars namely CH Cyg, UV Aur, HM Sge, RX Pup, V1016 Cyg and RR Tel are determined for the first time using IRAS-LRS data. Some of these stars showed an outburst activity which was caused probably due to hydrogen shell flash in the secondary white dwarf as a result of mass transfer from the primary M giant; while others had been relatively quiescent. All the stars showed indications of the presence of silicate dust grains except perhaps UV Aur. The dust temperatures in the symbiotic stars which had in the past an outburst activity are in general much smaller (by 400 K) than those in the symbiotics which had been quiescent and not shown any nova-like activity. Also there is an indication from our analysis that in the case of the former the dust masses are larger and the shells are spatially more extended than in the case of the latter. These results are given in detail in Table 1. Our results also indicate that the grain sizes could be larger, the earlier the outburst was, as revealed by the relative strengths of the 10 and 18 μ features in the case of the symbiotic novae. Our results support the hypothesis that during an outburst there would be a common envelope of dust blown farther and farther away by the nova wind resulting in the dust parameters described in the paper; while in the case of the quiescent symbiotics, the Mira dust envelopes get constantly heated up by the hot companion star.
Observations of Bipolar Mass Flow from Symbiotic Stars
Authors: Solf J.
Published: July 2016

Spectroscopic observations of high spatial and high spectral resolution indicate that mass flow from symbiotic stars generally exhibits a bipolar pattern. Besides the polar features moving at velocities up to several 100 km/s, equatorial structures of much lower expansion rate are present in some cases. Mostly, the high-velocity components appear to be highly collimated and hence can be considered as “jets”. The jets probably originate from an accretion disk within a binary star where mass from a late-type giant is accreted by a compact companion.
Photoionization models with accretion discs
Authors: Vogel M.
Published: July 2016

The diagnositic possibilities for identifying the ionizing source in symbiotic systems are explored. As possible sources we consider hot blackbodies and accretion discs. It turns out that main sequence accretors and hot blackbodies may have the same appearance in both, emission line and continuum flux distribution. However, UV continuum indices of models containing an accretion disc around a white dwarf are confined to a very small region, separated from main sequence accretors and blackbodies. Furthermore, if symbiotic systems containing a white dwarf accretor exist, they might be recognizable by strong emission in Fe X λ6374.
Accretion Disks in Symbiotic Stars
Authors: Duschl Wolfgang J.
Published: July 2016

We give an overview over the theory of geometrically thin α-accretion disks: further we introduce the two different proposed mechanisms that can cause outbursts of accretion disks: and finally we compare the results of these models applied to symbiotic stars (=SS).
CH Cygni Half a Century Ago – Changing Activity of the Cool Component
Authors: DziewulsKi Władysław , Muciek Marek , Mikołajewski Maciej
Published: July 2016

CH Cyg was observed visually by Professor Władysław DziewulsKi in the years 1930–1940 at the Vilno Observatory, with the 15 cm refractor using Argelander’s method. As a sKillful and experienced observer he achieved the accuracy of his single measurement of about 0.05 mag. The series of his 652 estimates of CH Cyg has been recently reduced and is discussed in this paper.

Apparently in those years the star was in relatively quiet state (like in the years 1970–1977), when in the visual region the light of only the red giant component of this binary is visible. We deduce it from:

a)

absence of any emission lines in spectra taKen by A. Joy in 1930 (Joy 1942)

b)

visual brightness of the star almost never exceeding 7.0 mag. what is typical for the quiet state of pure M6III spectrum

c)

red color, resulting from comparison of our visual brightnesses and the photographic ones published by S. Gaposchkin (1952)
Radial Velocities of CH Cygni Just as the Jets Appeared
Authors: Janaszak Ewa , Mikołajewski Maciej
Published: July 2016

The period of maximum brightness of CH Cygni which started in mid 1981 finished at the end of July 1984, when sudden drop by about 1 mag was observed (Fig.1). At the same time a radio outburst has occured and the jet structure has developed (Taylor et al.1986). The Toruń Observatory has recorded the spectra of CH Cygni just at this moment. Significant spectral variations, especially development of wide wings in Balmer emission lines have been found (Mikołajewski and Tomov 1985).

Mikołajewski et al. (1987) showed that the “shell” absorption lines roughly reflect the orbital motion of a hot companion of the M giant. Figure 1 presents radial velocities of these absorption lines of ionized and neutral metals (mainly TiII, FeI) together with the v.rad. followed from possible orbital solution suggested by Mikołajewski et al. About 3-4 days after the drop started the RVs of the “shell” absorption lines very quickly (during 3 days) got out of a deep local minimum (ΔV ∼15–20 km/s) preceding the drop by a mounth. The FeII emission lines, which are formed in the outer regions, do not show so large radial velocity variations ( Fig.1 ).
Symbiotic Star AG Pegasi - Retrospect and Prospects
Authors: Chochol D.
Published: July 2016

Symbiotic star AG Peg (HD 207757), which is still declining from the outburst in the last century, appears to be related to the very slow RT Serpentis type novae: binary stars consisting of a cool M giant and a hot component, which underwent outburst.

AG Peg was ninth magnitude star before the year 1850. Then it slowly rised in brightness and reached fifth magnitude in 1885. After the sudden drop of brightness in 1892 due to the dust formation in expanding envelope, the star returned to the sixth magnitude and then it was continuously decreasing in brightness (Lundmark, 1921; Rigollet, 1947; Belyakina, 1968). Nowadays the decrease of brightness is 0.021 mag/yr (Fernie, 1985).
Ultraviolet Variability of the Symbiotic Star AG PEG
Authors: Chochol D. , Komárek Z. , Vittone A.
Published: July 2016

Symbiotic star AG Peg consists of a hot subdwarf with a WN6 spectrum and a cool M3 giant, which is not filling its Roche lobe (Boyarchuk 1967, 1985). A detailed study of profiles, equivalent widths and radial velocities of emission lines in optical spectra allowed Hutchings et al. (1975) to conclude that a hot subluminous star approximately 1 M⊙ rotates rapidly and ejects material which streams towards the cool M giant with the mass 3-4 M⊙. UV observations seems to support this model.

UV observations provided from the databank of the IUE satellite were obtained in 1978–81 by different observers. The observational material consists of 12 high dispersion SWP spectra and covers the region 1200 – 2100 A. The spectra were reduced at Trieste observatory using standard IUESIPS package. The radial velocities of emission lines were measured on tracings and corrected for the motion of Earth and satellite.
Emission Line Analyses of HBV 475, V1016 CYG, and HM SGE
Authors: Tamura S.
Published: July 2016

Results of the high dispersion spectroscopic observations on HBV 475, V1016 Cyg, and HM Sge are presented. Due to yearly observations of HBV 475 since 1981, radial velocities which have been measured from Hα and Hγ can be explained by a bipolar like non-spherical flow combined with the rotation. Highly resolved profiles of Hα, [FeVII]λ6087, [0III] λλ4959,5007, and HeIIλ4686 are obtained from V1016 Cyg and HM Sge as well as HBV 475. Characteristic differences of them can be seen among these symbiotic stars.
Photometric and Spectroscopic Variations of the Symbiotic Star EG Andromedae
Authors: Skopal A. , Chochol D. , Vittone A. , Mammano A.
Published: July 2016

EG And is a symbiotic binary system. The cool component is an M3 III star, the hot one is a subdwarf with temperature 60 250 K and luminosity 1.45 L⊙ (Boyarchuk, 1985). The eclipsing nature of the system suggested from UV spectroscopy by Oliversen et al. (1985) was confirmed photometrically by Chochol et al. (1987). The circular spectroscopic orbit of cool component determined by Oliversen et al. (1985) supposing the orbital period 470 days leads to f(m) = 3.2×10−2 M⊙ and detached configuration.
The Third Galactic Carbon Symbiotic
Authors: Schulte-Ladbeck Regina E. , MacConnell D. Jack , Zarate Nelson
Published: July 2016

Of the more than 100 symbiotic stars now known in our Galaxy, only two have previously been reported to contain carbon stars as their cool components. We here present observations of a third such object, which we wish to call Weaver’s star since Weaver (1972) first identified it as a symbiotic.
Ultraviolet to Near Infrared Observations of BF Cyg
Authors: Cassatella A. , Gonzalez-Riestra R. , Fernandez-Castro T. , Fuensalida J. , Gimenez A.
Published: July 2016

In this paper we provide preliminary results of multifrequency observations of BF Cyg carried out in July 1986. The ultraviolet spectra were obtained on July 26, 1986 using the IUE satellite. The optical observations were made at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands) in July 1986 during the night 13/14 using the Isaac Newton 2.5m telescope with the Intermediate Dispersion Spectrograph (IDS, 500 mm camera) and the Image Photon Counting System (IPCS). The infrared observations were made during the night 13/14 of July, 1986, at the Observatorio del Teide (Tenerife, Canary Islands) using the Carlos Sanchez 1.5m telescope and an infrared single-channel photometer with an InSb detector.
The 1987 Outburst of the Recurrent Nova U SCO
Authors: Sekiguchi K. , Feast M.W. , Whitelock P.A. , Overbeek M.D. , Wargau W. , Jones J. Spencer
Published: July 2016

Spectral observations obtained soon after the 1987 brightening of U Sco support a thermonuclear runaway model for outbursts of this object. Spectra later in the decline are, however, more characteristic of a hot accretion disc. These observations are reconciled in a model where the low-mass high-velocity shell ejected from the surface of the white dwarf collides with the accretion disc causing it to brighten.
Summary of Final Discussion
Authors: Stencel Robert E.
Published: July 2016

The last session of the Colloquium was Chaired by Harry Nussbaumer and opened with statements from members of a panel comprised of Livio, Mikolajewska, Luud, Viotti, Magalliaes, Slovak, Kwok and Whitelock. Viotti began by comparing the available data for symbiotics historically and since IAU Colloquium 70 in 1981. He emphasized new UV, X-ray, infrared and radio observations. He also sketched the recent history of wavelength specific publications. Whitelock stated that it now seems clear all D-types probably contain Miras and that S-types do not evolve into D-types. Luud stated that his group intends to continue its near infrared observations with the 2 meter at Tartu, and that it is important to confirm conclusions based on IRAS data. He mentioned that masses for the Miras are needed given the discrepancy between observed and evolutionary masses.
Effects of Stellar Rotation on Spectral Classification
Authors: Slettebak Arne , Kuzma Thomas J.
Published: July 2016

Stellar rotation may affect the strengths of lines used in spectral classification because of effects of plate resolution and also because of physical changes in the rotating stellar atmospheres. In the first case, the importance of using standard stars with appropriate rotational line broadening in classifying spectra of relatively high dispersion (resolution) is emphasized. Rotational effects on weak lines in general and on the Balmer lines may cause systematic errors in the assignment of spectral types and luminosity classes unless the standard stars are chosen with line broadening similar to that of the star to be classified. With regard to physical changes in the rotating atmospheres, we have extended the earlier work of Collins to include the Balmer lines plus additional lines of He I and Si II which are important in spectral classification over a wider range of spectral types.
Investigation of the Properties of Large-Redshift QSOs using Slitless Spectroscopy
Authors: Smith Malcolm G.
Published: July 2016

The use of natural spectral-form groups (Morgan, 1951) on low-dispersion slitless survey plates efficiently isolates rather pure samples of intrinsically interesting extragalactic objects (e.g. Smith, 1975, 1976; Smith, Aguirre and Zemelman 1976; MacAlpine, Smith and Lewis 1977a, b; MacAlpine, Lewis and Smith 1977, MacAlpine and Lewis 1978, Cooke et al. 1977, Hoag and Smith 1977, Sramek and Weedman 1978, Bohuski, Fairall and Weedman 1978, Osmer and Smith 1979). One of these groups (illustrated for various telescopes by Smith 1975, Hoag and Smith 1977, Bolton et al. 1977 and Smith 1978) has been found to include a very large set of high-redshift QSOs. Definition of the group (e.g. Smith 1976) rests on the direct detection of the QSO emission lines on the survey plates. Objects already selected from the group range in redshift from 0.32 (PKS 2227-399 - see also Peterson and Bolton 1978, Browne, Savage and Bolton 1976, Bolton et al. 1977) to 3.45 (Q2227-6-3928 - Smith et al. 1977, Osmer 1978a) and in apparent magnitude from 21 (Osmer 1977, Smith 1978) to 16 (including the apparently brightest high-redshift object known, Q1101-264). - Osmer and Smith 1976, Smith 1978, Carswell et al. 1979 and the most luminous object known, Q0420-388 -Osmer and Smith 1977b; Wright and Kleinmann 1978). 15 of the 21 objects known with confirmed redshifts z > 3 have been discovered this way.
Correlation of Spectroscopic and Photometric Data
Authors: Hauck B.
Published: July 2016

This paper reviews first of all the various problems connected with the establishment of a relationship between MK type and various photometric parameters: reddening, binarity, rotation. Mention is then briefly made of the various relationships proposed in the literature for the UBV, uvbyβ, DDO, Vilnius and Geneva systems. The MK classification is a bidimensional classification which provides also indication of peculiarity (Ap, Am, Ba stars, for example). The problems arising from stars having a peculiar chemical composition are examined. The establishment of a relationship between a color index and the MK type or the location of the various MK types in a photometric diagram are both classical methods to obtain a correlation between a photometric system and the MK schema. However a new solution is proposed by the method of stellar boxes, which allows us to find all the stars having the same colors. If many photometric systems are limited in their possibilities of classifying all stars from O to M, the GENVIL (or VILGEN) system, formed with four filters of the Geneva system and three of the Vilnius system and at present under consideration, will certainly provide a very good means to this end. Finally, the new spectroscopic and photometric catalogues available at the Stellar Data Center in machine-readable form offer us the possibility of improving the present correlations.
The Reticon Spectrophotometer at Cima Ekar Observatory
Authors: Barbieri C. , Serego A. S. di
Published: July 2016

A spectrophotometer employing linear arrays of Reticon photodiodes has been used at Asiago observatory since August 1977. The first version, with a 128 - element array, has already been described in detail (Barbieri et al. 1978). The final configuration has 512 photodiodes, each 50.8 μm high, so that 2-5 cm of spectrum can be recorded in a single exposure. The spectrophotometer is mounted at the focal plane of the Boiler & Chivens spectrograph of the 182 cm telescope; with the 600 groves/mm grating the diode width corresponds to 5.9 Å. Two other gratings are available, respectively with 400 and 7200 grooves/mm. A fairly sophisticated computer system permits a remarkable flexibility of operation, with real time display on the CRT of the acquired data and recording on mag. tape. To subtract the thermal current and the sky, the star is taken out of the slit by tilting a transparent plate in front of the spectrograph, always under computer control; the astronomer can choose different star/sky exposure times so as to optimize the observing procedure. Guiding can be performed from the control cabinet with an integrating SEC-TV system.
Classification by Photoelectric Measurements of Molecular Bands: Current Status and Future Prospects
Authors: Wing Robert F.
Published: July 2016

As a classification technique, photoelectric narrow-band photometry is especially effective in the case of late-type spectra, in which molecular bands furnish the most sensitive criteria. Measurements of molecular bands with bandpasses of about 50 Å can be made very efficiently, and for normal stars they can be calibrated in terms of temperature and luminosity. In the case of normal late-type giants and supergiants, two-dimensional classifications can be obtained from measurements of TiO and CN; for very cool giants and for dwarfs it is useful siso to measure VO and CaH, respectively. All these molecules have bands in the red and near-infrared spectral regions, where cool stars are relatively bright and where photometric accuracy is highest.
High Dispersion Spectra of CP Stars: A Problem in Classification
Authors: Cowley C. R.
Published: July 2016

High dispersion (2.4 Å mm−1) spectra of chemically peculiar late B and A stars reveal a wealth of information. In this paper we attempt to organize this material by introducing a classification scheme based on the second spectra of the lanthanide rare earths. Four categories are introduced: a) Lanthanide Rich, b) Nd-Sm Anomalous, c) Iron Group-Rich, Rare Earth Moderate, and d) Lanthanide Normal. The variability that is possible in different stellar spectra of Nd II and/or Sm II relative to Ce II, Eu II, and Gd II is a prominent feature of the data. Thus far, the only means of detecting these variations is to use high dispersion spectra. The relationship between our classification and low dispersion spectroscopic and photometric criteria is a problem for the future.
The Forthcoming Morgan-Abt-Tapscott Spectral Atlas
Authors: Abt H. A.
Published: July 2016

Since the publication of the MKK atlas in 1943, there has been much progress in (1) the construction of fast spectrographs of higher resolution, C2) faster fine-grain emulsions and sensitizing techniques, (3) the partial or complete explanations of certain spectroscopic effects, [4) the discovery of other spectroscopic effects, and C5) refinements in the classification system based on new spectra and data on luminosities. An interim atlas entitled An Atlas of Low-Dispersion Grating Stellar Spectra was published in 1968 by Abt, Meinel, Morgan, and Tapscott but it is out of print and was not reissued in anticipation of the forthcoming greatly-improved atlas.
Classification Errors in Low-Dispersion Spectroscopy
Authors: Bruch A. , Buescher M. , Samson W. , Seitter W. C.
Published: July 2016

With the two parts of the Bonn Spectral Atlas it was hoped to provide a tool for the improvement of accuracy in low-dispersion spectral classification. Earlier estimates from our spectra by different observers with classification experience indicated a rather small increase in classification errors with decreasing resolution. They amount to 0.17 spectral types per 1000 Å mm-1 increase (larger numbers) in dispersion in the range 200 - 1300 Å mm-1 dispersion added to the 0.1 spectral types which are typical errors at MK classification dispersion near 100 Å mm-1 and 0.56 luminosity classes per 1000 Å mm-1 increase (larger numbers) in dispersion in the range 200 - 1300 Å mm-1 dispersion added to the 0.6 luminosity classes which are typical errors at MK classifications near 100 Å mm-1. In order to improve on the error determinations the three first-named authors, all graduate students with no previous experience in spectral classification, classified independently between 800 and 1300 spectra with each of the three Bonn Atlas dispersions of 240, 645 and 1280 Å mm-1. The classification errors of the three students differ by very small amounts and thus are averaged in the following discussion.
Spectral Classification of M Stars by Photo-Electric Techniques
Authors: Jones D. H. P.
Published: July 2016

In pursuit of a program (Jones 1976, 1977) to establish the mass function of stars in the solar neighborhood it has been necessary to establish whether many faint red stars are dwarfs or not. If they prove to be dwarfs then their luminosities are needed to derive their photometric parallaxes. The first approach (Jones 1973) used interference filters with the following wavelengths (in Å): 6076 Window; 6830 CaH; 7100 TiO; 7460 Window. The band passes are all roughly 30 Å. The magnitude difference m(6076) - m(7460) is comparatively free from blanketing by atomic lines and molecular bands and so provides an estimate of color temperature. As shown in the top panel of Fig. 1., the CaH; TiO ratio m(6830) - m(7100) is a powerful discriminant in separating M dwarfs from M giants and supergiants. The color m(7100) - m(7460) measures spectral type; the types so derived prove to be in good accord with those of Morgan and Keenan (1973), Wing (1973, 1978) and Wing et al. (1976). The three lower panels of Fig. 1 show the application of this technique to three objective prism surveys of faint red stars. MBT refers to McCarthy, Bertiau and Treanor (1964) who made a near infrared survey covering 165 square degrees in the South Galactic Cap. The dwarfs can be easily separated when they are redder than m(6067) - m(7460) = -1. The frequency of giants and dwarfs as a function of m(7460) is shown to the right. U refers to Upgren (1960) who made a blue survey covering 400 square degrees in the North Galactic Cap. In contrast to the near infrared, the blue region of the spectrum allows luminosity discrimination. Upgren’s luminosities are in good accord with those derived here. However, working to a fixed blue magnitude limit introduces a bias against the reddest dwarfs which emerges when U is compared with MBT. The lowest panel is based on the square degree area discussed by Murray and Sanduleak (1972) which was based in turn on the near infrared survey by Sanduleak (1964). Most of the interference filter observations were made with the 2.5m
Systematics of Dwarf Novae
Authors: Warner B.
Published: July 2016

From about 30 Dwarf Novae with the best determined distances the following relationships are found.

(i)

a tight correlation between absolute magnitude at maximum light, Mv (max), and orbital period, P.

(ii)

a correlation between Mv (min) and P showing wide scatter.

(iii)

a correlation between Mv (mean), the mean absolute magnitude averaged over normal outbursts, and P, again with wide scatter. The scatter is shown to correlate strongly with outburst timescale Tn.

(iv)

a strong correlation between range, Mv (min) - Mv (max), and Tn (the Kukarkin-Parenago relationship).

(v)

a strong correlation between range My. (mean) - Mv (max), and both Tn and P.

This final correlation is interpreted in terms of the disc instability model of dwarf novae and successfully predicts the observed width of outburst versus P relationship.
Collective Properties of a Magnitude-Limited Sample of Cataclysmic Binaries
Authors: Ritter H.
Published: July 2016

Results of an analytical discussion of observational selection in a magnitude-limited sample of cataclysmic binaries (CBs) are presented. It is shown that the dependence of the strength of selection in favour of massive white dwarfs, of the mean orbital inclination and the fraction of eclipsing systems in a sample on the limiting magitude mv reflects the large-scale distribution of CBs in the galaxy and the influence of interstellar absorption. Furthermore it is shown how selection in favour of massive white dwarfs depends on the mass radius relation of white dwarfs.
Cataclysmic Variables in a White Dwarf Survey at the South Galactic Pole
Authors: Bues I.
Published: July 2016

During a ¡photometric and spectrophotometric survey of 200 white dwarf candidates with in a field around the South Galactic Pole two new cataclysmic variables have been identified and new observations of one already known object have been accumulated. Observations in the visible and UV-region show variability and differences in spectral type. If compared to the numbers of cataclysmic variables/white dwarfs as computed by Ritter and Burkert (1985)there is a shortage of a factor of 5.
Mapping the Line Emission Distribution of Cataclismic Variable Stars
Authors: Marsh T.R. , Horne K.
Published: July 2016

We describe a method for imaging the accretion disc of a Cataclysmic Variable star. We use the two-dimensional information contained in the line profiles as they vary with phase to invert the line formation process. Asymmetries in the disc, as are caused by the bright-spot, for example, are accounted for naturally.
Spectroscopy of the Primary and Secondary Components of the Dwarf Nova AH Herculis
Authors: Bruch A.
Published: July 2016

The dwarf nova AH Her belongs to those cataclysmic variables which show a composite spectrum in the optical range, containing emission lines from the accretion disk and absorptions from the secondary star. This has been shown by Horne et al. (1986). Anticipating the composite nature of the spectrum from the the B-V colour of AH Her, which is intrinsically redder then , I took spectra of the system in four nights in June 1984 at the 1.2-m-telescope of the DSAZ on Calar Alto in order to detect the secondary component. The wavelength range observed was 5300 Å – 7150 Å. Apart from H in emission which behaves in the same way as described by Horne et al., the spectra show in fact a definite absorption of the Na D lines to be attributed to the secondary star. The linestrength and the absence of any strong TiO features confines the spectral type of the secondary to between K2 and MO. It is possible to calculate the relative contributions of the primary and secondary to the total light at the wavelength of Na D as a function of the exact spectral subtype of the secondary, using the measured equivalent width of the Na D lines. Taking the spectral gradient of primary and secondary from the current literature the same can be done for the effective wavelength of the V band. It is then straightforward to calculate the system’s absolute visual magnitude and the distance. It turns out that AH Her is one of the intrinsically brightest dwarf novae known, regardless of the exact spectral subtype of the secondary.

A complete account of the observations of AH Her and of the interpretations is given in a paper which has been submitted to Astronomy and Astrophysics.
Long-Term Optical Photometry of the Dwarf Nova VW Hyi
Authors: Van Amerongen S.F. , Van Paradijs J.
Published: July 2016

Long-term five-colour photometry of the dwarf nova VW Hyi shows no evidence for a secular change of the flux during the quiescent interval between normal outbursts (3σ upper limits between 0.16 and 0.20 mag in the five passbands). However, the amplitudes in the orbital B-U and U-W colour curves change during quiescence. A delay in the progress of normal outbursts toward higher frequencies confirms the delay, seen with IUE, in the onset of a normal outburst toward higher frequencies. Just after outburst, the system is substantially bluer than later in quiescence.