bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Equilibration on the X-ray Intensity of Sedov Models
Authors: Jerius D. , Teske R.G. 
Published: July 2016

AbstractWe have synthesized a set of SNR X-ray and coronal iron surface brightness profiles to determine observational constraints to help distinguish how the remnants’ ion-electron energy equilibration time-scales compare to their ionization time-scales. The profiles are based on Sedov-Taylor blast wave models under the two scenarios (1) equal Tion and Te or (2) Coulomb equilibration of Te and Tion. Resultant spectra were convolved with Einstein HRI and IPC sensitivity curves to simulate satellite observations of actual remnants.
Long Slit Echelle Spectroscopy of Supernova Remnants in M33
Authors: Blair William P. , Chu You-Hua , Kennicutt Robert C. 
Published: July 2016

AbstractWe have obtained long slit echelle spectroscopy for 10 of the brightest supernova remnants in M33 using the KPNO 4 m telescope. The profiles at Hα indicate bulk motions in the range 100–350 km s−1 in these remnants. Nearly all of the objects show signs of contamination by low velocity H II emission at some level. This affects the line intensities measured from low resolution data and may affect diameter measurements of these remnants.
VLA Observations of SNRs in M33
Authors: Duric N. 
Published: July 2016

AbstractThe results of a VLA study of the radio continuum properties of supernova remnants in the nearby spiral galaxy M33 are presented. It is shown that a relationship exists between the radio surface brightnesses and the diameters of the 13 detected supernova remnants. The significance of the relation and the constraints it imposes on models of SNR evolution are discussed.
New Supernova Remnants from Deep Radio Continuum Surveys
Authors: Reich, W. , Fürst E. , Reich P. , Junkes N. 
Published: July 2016

AbstractBased on radio continuum surveys of the Galactic plane at wavelengths of 21 cm and 11 cm we have so far identified about 32 new supernova remnants in the area 357°.4 ≤ℓ≤ 76°. |b| ≤ 5°. This increases the number of known objects in this field by about 68%. Most of them are in the Galactic latitude range |b| 〉 0°.5. Some implications are discussed.
Supernova Remnants and the ISM: Constraints from Cosmic-Ray Acceleration
Authors: Wandel Amri 
Published: July 2016

AbstractSupernova remnants can reaccelerate cosmic rays and modify their distribution during the cosmic ray propagation in the galaxy. Cosmic ray observations (in particular the boron-to-carbon data) strongly limit the permitted amount of reacceleration, which is used to set an upper limit on the expansion of supernova remnants, and a lower limit on the effective density of the ISM swept up by supernova shocks. The constraint depends on the theory of cosmic ray propagation: the standard Leaky Box model requires a high effective density, > 1cm−3, and is probably inconsistent with the present picture of the ISM. Modifying the Leaky Box model to include a moderate amount of weak-shock reacceleration, a self consistent solution is found, where the effective density in this solution is ≈ 0.1 cm−3, which implies efficient evaporation of the warm ISM component by young supernova remnants, during most of their supersonic expansion.
Infrared Spectroscopy of Supernova Remnants
Authors: Moorwood A.F.M. , Oliva E. , Danziger I.J. 
Published: July 2016

AbstractSpectra of several galactic and LMC supernova remnants have been obtained at R ~ 1500 in the 1−2.5 µm region with the cooled grating/array spectrometer, IRSPEC, on the ESO 3.6m telescope. The brightest lines observed are from [FeII]. In RCW 103, which exhibits the highest surface brightness, H (Brγ at 2.17µm) and H2 (1−0 S(1) at 2.12µm) lines have also been detected. A good correlation is found between [FeII] (1.64µm) and Hβ implying similar ionization structures and Fe abundances in a wide variety of remnants. The actual [FeII](1.64µm)/Hβ ratio of ~0.2 also implies a high depletion factor (>0.9) for Fe. Electron densities, extinctions and [FeII] luminosities derived from these data are presented and discussed and attention drawn to a potentially interesting discrepancy between H(Brγ) and Hβ fluxes.
Infrared Observations of Symbiotic Miras
Authors: Whitelock Patricia 
Published: July 2016

AbstractSymbiotic Miras are identified by their infrared characteristics. It is shown how an understanding of the evolutionary position of normal Mira variables together with the empirically established period luminosity relation can be used to derive various physical parameters for similar objects in symbiotic systems. The pulsation periods of symbiotic Miras measured so far fall between 280 and 580 days, their ages must be in the 5–10 Gyr range while main sequence masses of the order 1 to 1.5 M⊙ are indicated. The obscuration events seen in the IR light curves of several symbiotic Miras are highlighted as potentially important and possible causes are discussed.
Ionization models of symbiotic stars
Authors: Nussbaumer H. 
Published: July 2016

SummaryA model of a symbiotic system is outlined. We present evidence that the main ionization mechanism responsible for the symbiotic nebula is radiative and not collisional. For calculating fractional ionization throughout the emission region we take either a blackbody source or an accreting system. If the ionizing radiation is due to accretion, the boundary layer between accreting star and disc provides the bulk of the ionizing photons. The possibility for distinguishing between different ionization sources are briefly discussed. C/N and O/N abundance ratios, calculated with the outlined ionization model places HM Sge, RS Oph, and T CrB among the novae and not among the symbiotic stars.
The Decay Time after a Thermonuclear Flash
Authors: Orio Marina 
Published: July 2016

AbstractThe drag luminosity produced by a secondary embedded in a nova envelope is calculated and it is assumed to liberate gravitational energy. The results of a preliminary calculation show that the time for envelope ejection and therefore for the light decay varies sharply with the binary distance. It would be considerably reduced if the binary distance is a < 2 RO. It is suggested that this is the main difference between the thermonuclear runaway of symbiotic stars and nova systems, instead of other physical parameters.
A P Cygni Profile for the He 10830 A line of CI Cyg in Eclipse
Authors: Bensammar S. , Friedjung M. , Letourneur N. , Maillard J.P. 
Published: July 2016

AbstractInfrared spectroscopic observations of CI Cyg in eclipse show a P Cygni profile for He I 10830 Å, with a wind velocity of the order of 150 km/s, not seen in hydrogen Brackett and Paschen emission lines, which are single peaked.
Symbiotic Eclipsing Binary Star CI CYG. The Cold Component Variability
Authors: Belyakina T.S. 
Published: July 2016

AbstractIt has been shown that the cold component of CI Cyg eclipsing binary system is a variable star. The amplitude of its light variations is close to with the time interval of 40–60 days.This star being the red giant M4 can be attributed as SR type variability. The light variations is caused by its temperature variations.
The Spectrum of CH Cygni - a Search for Rapid Line Variations
Authors: Tomov T. , Raikova D. 
Published: July 2016

The spectacular changes of CH Cyg spectrum during the last period of activity and the flickering in short wavelength light suggest the possibility of rapid line variations (Walker et al.,1969). In November 1982 a series of spectral observations has been accomplished at Rozhen Observatory to investigate the subject.In that period the spectrum of CH Cyg is dominated by type A shell lines. They are supposed to originate in an accretion disk surrounding the hot star of the binary system. The flickering in the optical wavelengths is characteristic for CH Cyg during periods of activity. Evidently it is related with the mass transfer. The investigation of its origin and relations with the other observational characteristics of the star could elucidate the accretion mechanism in this system.
A Model for RX Puppis
Authors: Allen David , Wright Alan 
Published: July 2016

The dust-rich (D-type) symbiotic stars appear always to comprise a mira variable and a star of temperature ∼ 105 K which ionizes the mira’s circumstellar envelope. On timescales of decades they change little, save for the slow pulsation of the mira at infrared wavelengths. RX Puppis is a striking exception to this generalization, however, since it undergoes extraordinary changes.RX Pup drifts between two extremes, exhibiting intermediate states. Table I summarises the known characteristics in the extreme states. Because of its variability, models of RX Pup are more highly constrained, giving us a chance to understand one of the D-type symbiotics.Optical spectra of RX Pup from the Anglo-Australian Telescope. Tie breadth of the lines in 1976 may be due to lower spectral resolution.
A New Absorption-Line Orbit for the Symbiotic Nova AG Pegasi
Authors: Slovak M.H. , Lambert D.L. 
Published: July 2016

AbstractPrecise cross-correlation absorption-line velocities have been derived using high resolution near infrared coude’ spectra for the symbiotic nova AG Pegasi. A revised weighted orbital solution is presented based on both extant photographic and the new absorption-line velocities.
Spectroscopic Variations of the Symbiotic Nova PU VUL
Authors: Hric L. , Chochol D. , Kovachev B. 
Published: July 2016

AbstractEvidence for formation and subsequent expansion of an A–F supergiant envelope in the very slow symbiotic nova PU Vul caused by quasiperiodic injections of matter from M giant to the A–F supergiant is given.
IUE and Optical Observations of HE 2-104
Authors: Lutz Julie H. 
Published: July 2016

AbstractHe 2-104 has been classified as both a planetary nebula and as a symbiotic star. Optical and ultraviolet spectra and CCD images have been obtained in order to learn more about the evolutionary state of this object. The spectra of the object indicate that it could be either a symbiotic star or a very high excitation planetary nebula. The CCD images show a nebulosity with a radius of about 4 seconds of arc and faint bipolar outer structures extending out approximately 25 seconds of arc from the center of the nebula.
Unravelling the Multiple Component Radio Emission of RS OPH in Outburst
Authors: Taylor A.R. , Bode M.F. , Davis R.J. , Porcas R.W. 
Published: July 2016

AbstractVLBI observations of RS Ophiuchi during its 1985 outburst enable us to start to disentangle the multiple component radio emission. It appears that the emission at low frequencies was predominantly non–thermal, whereas at high frequencies the emission is most likely thermal. It is then possible to probe the physical properties of the remnant.
Criteria and Applications of the MK Classification (Early Type Stars)
Authors: Lodén Kerstin 
Published: July 2016

AbstractThe fundamental characteristic of the MK classification system is the definition of an array of standard stars, arranged in two dimensions. New techniques and an enormous increase in observational and theoretical work since the original catalog in 191+3 have in various ways complicated the problem of spectral classification. Problems discussed are: 1.) The re-examination of standard stars; 2.) The optimum dispersion and the limits of dispersion for MK classification; and 3.) Some groups of peculiar objects.
Les Étoiles Supergéantes Dans le Grand Nuage de Magellan. La Signification des Classes de Luminosite I
Authors: Fehrenbach Ch. 
Published: July 2016

AbstractLes classes de luminosité de Keenan et Morgan sont une subdivision très commode pour caractériser les étoiles d’une même classe spectrale. Les classes V et III paraissent bien définir un type d’étoiles; leurs paramètres principaux (MB et Te ou pe et Te) sont déterminés par le type spectral et la classe de luminosité. Les classes IV et II sont mal définies, leur existence n’est pas assurée. L’ensemble des étoiles supergéantes est encore plus mal défini, elles remplissent complètement la partie supérieure de diagramme de Russell-Hertzspung. Une étude de ce diagramme pour les étoiles supergéantes du Grand Nuage de Magellan montre que les subdividions IaO, la, lab et Ib correspondent à une variation continue de la magnitude absolue qui va par exemple des étoiles AO de -9.6 à -5. La valeur souvent admise -7 pour la magnitude absolue des supergéantes est une simplification abusive. D’autre part, la classification exacte des luminosités est difficile et une mesure d’une quantité physique (rapport d’intensité de raies, ou intensité de raies) devrait permettre une meilleure classification de ces étoiles.
Spectral Classification from a Theoretical Point of View
Authors: Bohm-Vitense Erika 
Published: July 2016

AbstractWe study the conditions under which a two-dimensional spectral classification according to Teff and ne is possible and when 3- or It-dimensional spectral classification is necessary because the classification criteria are unavoidably influenced by the metal and helium abundances. For late type stars, where molecular absorption becomes important for the continuum a seven-or more- dimensional classification may be necessary. At this point spectral classification may not be useful any more. We find generally that a derivation of the gravitational acceleration from the spectroscopically determined electron density is only possible if the helium abundance is known.
A Deep Objective Prism Survey of Two Regions in the Large Magellanic Cloud for Ob and Supergiant Stars
Authors: Davis Philip A. G. , Sanduleak N. 
Published: July 2016

AbstractTwo regions in the Large Magellanic Cloud (centered atα = 5h 11m, δ= -66° 08’ (34B), α = 5h 27m, δ= -72° 15’ (47B) have been searched for OB and supergiant stars. A catalogue of 312 stars is presented in which objective prism spectral types, positions (1975), approximate B magnitues and cross identifications are given. About half the stars catalogued in each area are OB stars, the remainder are supergiants. The region at δ=-72° has two to three times as many F and G-type supergiants as the region at δ= -66°.
Two Dimensional Spectral Classification of Early Type Stars by Narrow Band Photometry
Authors: Gerbaldi M. , Morguleff N. 
Published: July 2016

AbstractSpectrophotometry data of 775 early type stars in a narrow band photometric system are analyzed, looking for the best parameters for a two dimensional spectral classification in the spectral region 3575 Å - 6000 Å. A correlation is established with the MK classification. The statistical technique of Principal Componant Analysis is applied to determine the number of linearly independent parameters among the data.
The Formation and Evolution of Low-Mass Close Binaries with Compact Components
Authors: Tutukov A.V. , Yungelson L.R. 
Published: July 2016

AbstractWe discuss the formation and evolution of interacting low-mass close binaries with a He-ICO- or ONe-dwarf neutron star or a black hole as a compact component. Mass exchange leads to cataclysmic events in such systems. The rate of semidetached low-mass close binary formation is 5×10−3 yr−1 if the accreting component is a He degenerate dwarf, 5×10−3 yr−1 if it is a CO-dwarf and 3×10−8 yr−1 if it is a neutron star. Systems with compact accretors arise as the result of the common envelope phase of close binary evolution or due to collisions of single neutron stars or dwarfs with low-mass single stars in dense stellar clusters. Evolution of LMCB to the contact phase in semi-detached stages is determined mainly by the angular momentum losses by a magnetic stellar wind and radiation of gravitational waves. Numerical computations of evolution with momentum loss explain observed mass exchange rates in such systems, the absence of cataclysmic variables with orbital periods 2h−3h, the low number and the evolutionary status of systems with orbital periods shorter than 80m. In conclusion we list unsolved problems related to magnetic stellar wind, the distribution of young close binaries over main initial parameters, stability of mass exchange.
Echelle-Mepsicron Time-Resolved Spectroscopy of the Dwarf Nova SS Cygni
Authors: Echevarría J. , Diego F. , Tapia M. , Costero R. 
Published: July 2016

AbstractHigh dispersion time-resolved spectrograms of the dwarf nova SS Cygni, obtained with the Echelle-Mepsicron system, show double peaked emission lines with a complex profile. The intensity of the Hβ line appears to be modulated by the orbital period. Radial velocity measurements of the wings of Hβ and of the absorption line system of the late-type star yield semiamplitude values of Kem = 101 ± 6 km s−1 and Kab = 151 ± 7 km s−1, respectively. Radial velocity measurements of the blue and red peaks and of the central absorption of Hβ reveal a synchronous movement with the broad wings, although there is some evidence of a narrow component probably associated with a hot spot in the disk or a chromospheric emission line from the secondary star. The Hβ modulation, the double profile and recently discovered UBV light variations support an inclination angle i ~ 50°. The masses of the primary and secondary stars using this angle and the observed semiamplitudes are Mp = 0.60 M⊙ and Ms = 0.40 M⊙, respectively. A detailed analysis of the absorption lines reveals a spectral type of K2V.
Some Notes on SS Cygni
Authors: Mirzoyan L.V. 
Published: July 2016

AbstractThe results of photoelectric and spectral observations of SS Cyg are briefly discussed. Some features of the spectral variations observed during a large outburst of SS Cyg can probably be explained using a model of a double star which is surrounded by an absorbing gaseous shell. It is noted that the existing data are not numerous enough for the explanation of the SS Cyg variability, in particular, its short-term variations.SS Cyg is a spectroscopic binary star with a 0.d276 period. The components of this system are dwarf stars (M ≈ 5.m5 for both stars), with dG5 and sdBe spectra; they probably show eruptive activity (Joy, 1956). In the spectrum of the B-component strong emission lines are observed. The dG5 spectrum is observed only in the minimum of SS Cyg.There are various investigations of SS Cyg, but up to now the cause of its variability, in particular, its rapid variability has not been determined. In addition, there are many other observations which have not been explained.
Photometry of TT Arietis
Authors: Semeniuk I. , Schwarzenberg-Czerny A. , Duerbeck H. , Hoffmann M. , Smak J. , Stepień K. , Tremko J. 
Published: July 2016

AbstractAn analysis of data spanning 24 years shows that a secondary 20m periodicity is a persistent feature in photometric observations of TT Ari. This period decreases from 27m in 1961 to 17m in 1985. The 4d beat period of photometric and spectroscopic periods is also apparent in observations of 1966.
Preliminary Results of Improved Model Fits to the Extreme and Far UV Observations of Cataclysmic Variables
Authors: Carone T.E. , Polidan R.S. , Wade R.A. 
Published: July 2016

AbstractWe present the first results of a study which will attempt to analyze the combined Voyager and IUE observations of cataclysmic variables using steady-state accretion disk models. Initially we use flux ratio diagrams to determine if a combination of models will suffice or if new ingredients are necessary.
New Exosat Observations of TV Columbae: Preliminary Results
Authors: Schrijver J. , Brinkman A.C. , Van Der Woerd H. 
Published: July 2016

AbstractThe first results of the analysis of new EXOSAT observations of the DQ Her type cataclysmic variable TV Col are presented. The period of the 1–10 kev X-ray pulsation associated with the white-dwarf rotation is now established as 1911 s. The pulsations are most pronounced in the lower energy channels (1–3.5 keV). The X-ray light curve shows absorption features associated with the orbital period of the system.
Periodic Variabilities in the IUE Spectra of SS Cygni
Authors: Lombardi R. , Giovannelli F. , Gaudenzi S. 
Published: July 2016

AbstractThe analysis of the IUE low resolution spectra of SS Cyg in quiescence clearly shows modulations with the orbital phase of the continuum and the emission lines total area. The shape of such modulations is depending on the type of the optical outburst preceding the quiescent phase in which the UV spectra were collected. This behaviour, together with those in other wavelength regions, could be explained within the framework of the intermediate polar models.
Accretion Disk Evolution
Authors: Bath G.T. 
Published: July 2016

AbstractThree aspects of mass transfer instability models of dwarf novae are examined. The hydrodynamic development of instabilities in the secondary are examined within Roche geometry and shown to extend at least a few degrees away from the line of centres. The form of the outburst light curves observed in SS Cygni are shown to be a natural consequence of mass transfer bursts with a duration either less than, or greater than, the disk viscous timescale. Finally the two-dimensional structure of the disc in the plane of the orbit is studied. As with α-disks the viscous evolution time following a burst of mass transfer determines the size of viscosity within the disk. Significant deviations from axial symmetry are found to be present.
Accretion Disk Boundary Layers: Their Structure and Stability
Authors: Stanley G.Q.G. , Papaloizou J.C.B. 
Published: July 2016

AbstractThe importance of the boundary layer has been known for some time, (see Lynden-Bell and Pringle. 1974). Yet this region of the disc has never been studied in great depth. We present here some calculations which are undertaken in order to explore some of the complex processes which can go on in this region. It is shown how the structure of the boundary layer is affected by viscosity, how oscillations can occur in the outer disk and boundary layer regions. We also show how they disperse and dissipate.
X-Ray and Optical Observations of the AM Her Star H0139−68
Authors: Schwope A. , Beuermann K. 
Published: July 2016

AbstractWe summarize results of our ongoing analysis of optical and X-ray data on the AM Herculis type binary H0139−68 (see also Beuermann et al., 1984; Schwope and Beuermann, 1985).
H2215−086 / Fo Aqr: The “King” of Intermediate Polars Spins Down
Authors: Pakull M.W. , Beuermann K. 
Published: July 2016

AbstractOur 5-color photometric observations of the intermediate polar H2215−086/FO Aqr which were collected between 1982 and the end of 1985 reveal that the 20.9 min rotational period increases with a spin-down rate of (1.0±0.2) 10−10 ss−1. This is in marked contrast to the spin-up behaviour of other well studied DQ Her systems.The pulse profile of the optical modulation as a function of wavelength changes drastically across the Balmer jump suggesting the presence of two distinct components of pulsed optical emission which furthermore are shifted in phase with respect to the X-ray maxima observed with EXOSAT.The UV, optical and IR flux distribution can adequately be accounted for by an accretion disc model with a mass-flow rate Ṁ = 1017 g s−1 and an inner boundary which is ≈10 times larger than the radius of the white dwarf. Our results support the magnetic accretion torque theory worked out by Ghosh and Lamb which can account for both spin-up and spin-down of the accreting star depending on the value of the fastness parameter ωs.We derive a magnetic moment μ ≈ 1.0 1033 G cm3 which will allow H2215−086 to evolve into an AM Her system once it has crossed the 2–3 h period gap.