bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orbital Radial Velocity Curves of Symbiotic Stars
Authors: Garcia Michael R. , Kenyon Scott J. 
Published: July 2016

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

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

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

A compact star in a detached binary system can accrete the matter from the stellar wind of the companion. In this case a more or less radial accretion flow is formed. By analogy to stellar winds from early type stars it is usually believed that the accretion of this sort should produce inverse P-Cygni profiles in resonance lines. However, there are physical differences between the wind and the radial accretion which can alter the outgoing profile significantly.The matter outflowing from an early type star cools off very fast due to the adiabatic expansion. However, it remains highly ionized as the quickly decreasing density does not allow it to recombine. Therefore the principal mechanism for the resonance line formation here is the scattering of the stellar continuum photons in the wind.
Colliding Winds in Symbiotic Systems
Authors: Kwok Sun 
Published: July 2016

AbstractThe physics of colliding winds in symbiotic systems is reviewed. The theoretical predictions are compared with observational data of symbiotic novae, in particular the recently erupted system HM Sge. It is suggested that the spectral behaviour of HM Sge from X-ray to radio can be explained by the colliding winds process.
AG Dra a Symbiotic Star With an Uncommon Cool Component
Authors: Friedjung M. 
Published: July 2016

SummaryAG Dra is probably a metal poor symbiotic binary of the galactic halo. The luminosity of the cool component is uncertain, which contributes to doubts about the correct model. Behaviour in activity is non classical with high ionization emission lines still having been seen then in the spectrum. This may perhaps most easily be explained by a weak thermonuclear event.
The Formation and Evolution of Symbiotic Stars
Authors: Webbink R.F. 
Published: July 2016

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

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

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

AbstractA scheme of automatic MK spectral classification is presented. It is based upon standard spectrograms obtained for visual spectral classification. Computer results are given for all the MK standard stars earlier than Bl. They are well correlated with the MK system. However, the results might be improved by using a rapid-scanning Michelson Fourier Transform Spectrophotometer to obtain the stellar spectra. The analysis of the interferograms should also be made by a computer.
Initial Results With the Objective Prism of the Uk Schmidt Telescope
Authors: Brück M. T. 
Published: July 2016

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

AbstractThe recently developed Kodak emulsions IIIa-J and IIIa-F have been used as a new tool for deep-survey photometry. Among their most useful features are the following: (i) fine to very fine granularity; (ii) very high resolving power; (iii) high sensitivity over a large wavelength range in the optical part of the spectrum.Some numerical results obtained from scanner data of a variety of normal star types, and from the spectral sensitivities of these Kodak plates combined with various optical filters are presented. We study the effects of these filters on the resulting synthetic colors with respect to the intrinsic potential of the colors to classify faint stars. In addition we briefly discuss the effects of interstellar reddening and the calibration of the photographic colors through photoelectric UBV photometry.This synthetic approach to multicolor photometry is discussed in the more general context of the relations between spectral classification, stellar photometry, and model atmosphere calculations. This context is the natural basis for galactic astronomy.
Recurrence Behaviour of Outbursts in VW Hyi
Authors: Van Der Woerd H. , Van Paradijs J. 
Published: July 2016

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The present paper restricts to the analysis of some passages from the Vedic literature, viz. Śatapatha Brāhmaṇa and Vedāṅga Jyautiṣa, from the view point of mathematical astronomy.The Śatapatha Brāhmaṇa in 2.1.2.1 to 2.1.2.5, refers to some ritual in which some fire has to be set up. It recommends Kṛttikā as the nakṣatra or the lunar asterism under which to set up the fire. For, there are some special features that Śatapatha-Brāhmana obviously considers as good points. According to the text, one good point about Kṛttikā is that it is ′the most numerous′; secondly, it rises ′in the east′.