bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinematics of Oxygen-Rich Filaments in Puppis A
Authors: Winkler P. Frank , Tuttle John H. , Kirshner Robert P. , Irwin Michael J. 
Published: July 2016

AbstractWe 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

AbstractWe 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

AbstractExisting 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

AbstractThe 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

AbstractA 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

AbstractWe 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

AbstractSome 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

AbstractThe 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

AbstractWe 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

AbstractAn 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

AbstractSuperbubbles 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

AbstractNew 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

AbstractGas 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’ NoteAt 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

AbstractThe 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

SummarySymbiotic 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

AbstractSpectroscopic 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

AbstractThe 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.
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 spectrumc)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

AbstractResults 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.
The Third Galactic Carbon Symbiotic
Authors: Schulte-Ladbeck Regina E. , MacConnell D. Jack , Zarate Nelson 
Published: July 2016

AbstractOf 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.
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

AbstractSpectral 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.
Effects of Stellar Rotation on Spectral Classification
Authors: Slettebak Arne , Kuzma Thomas J. 
Published: July 2016

AbstractStellar 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.
Correlation of Spectroscopic and Photometric Data
Authors: Hauck B. 
Published: July 2016

AbstractThis 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.
Classification by Photoelectric Measurements of Molecular Bands: Current Status and Future Prospects
Authors: Wing Robert F. 
Published: July 2016

AbstractAs 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

AbstractHigh 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

AbstractSince 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.