bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Evolution of Binary Stars into Contact States
Authors: Hilditch R W 
Published: July 2016

AbstractGood-quality empirical results on 62 short-period binary stars recently summarised by Hilditch & Bell (1987) and Hilditch, King & McFarlane (1988) are discussed in terms of evolutionary paths from detached to semi-detached and contact states. These data suggest two evolutionary paths to the contact binaries - from detached systems directly into contact to form initially shallow-contact systems, and via case A mass transfer to semi-detached states, thence to contact systems. These empirical results support previous arguments based on evolutionary models and less detailed observational data.Concern is expressed about the paucity of high-quality spectroscopic data, particularly for low-mass systems displaying EB-type light curves and the resultant limitations on analyses of those light curves. Such systems provide tests of evolution into contact for the first time, or of broken-contact phases for WUMa-type binaries. The crucial importance of long-term monitoring (decades) of times of minima as indicators of mass transfer rates amongst these interacting binaries is also noted.
Who is Who in Algol-Land ? - Part II -
Authors: Packet W. , De Greve J.P. 
Published: July 2016

AbstractIn part I (De Greve and Packet) we have investigated the occurrence of reversed phases of mass-transfer during Case A evolution in close binaries. If the initial period of a system is shorter than 1 - 2 days (Early Case A) the reversed phase starts before core hydrogen exhaustion of the gainer (part I). This type of evolution is characterized by at least two phases of slow mass-transfer.We have computed the evolution of four Early Case A systems with initial masses of the loser equal to 3 Mo and 5 Mo. These four systems start mass-exchange when Xc of the primary has decreased to 0.525 (75% of its initial value). They all experience two phases of slow mass-transfer.We find that both phases have about the same duration for all systems. The mass ratios are clearly distinct, being closer to unity during the first phase. In the Hertzsprung-Russell, mass-radius and mass-luminosity diagrams both components remain close to the main-sequence band during slow mass-transfer. Evolution as an Algol is ended when both components overflow their outer critical surface after a second reversal of the mass-transfer.Observed Algol systems evolving in Early Case A are scarce. A search thruogh the catalogue by Giuricin et al. gives us the following candidates: X Tri, SX Aur and V Pup. Based on their mass ratios, SX Aur can tentatively be assigned to the first phase of slow mass transfer and X Tri to the second phase. For V Pup (which is more massive) this choice can not be made with certainty.
Spectroscopy and Optical/IR Photometry of the Cataclysmic Variable CPD-48° 1577
Authors: Wargau W. , Bruch A. , Drechsel H. , Rahe J. , Schoembs R. 
Published: July 2016

AbstractThe photometric variability of CPD-48°1577 in the optical and IR ranges is discussed. The structure and variation of prominent emission line profiles are investigated. An estimate of the distance is given.
Photometric and Spectroscopic Study of R CMa
Authors: Radhakrishnan K. R. , Sarma M. B. K. , Abhyankar K. D. 
Published: July 2016

AbstractUVB Flight curves and spectrograms of R CMa obtained with the 48-inch telescope of Japal-Rangapur Observatory during 1980-82 have been used for deriving the eclipse and orbital elements as well as the absolute dimensions of the components. The primary is found to be a Main-Sequence F2V star of mass 1.52 M⊙ and the secondary a subgiant star of spectral type G8 and mass 0.20 M⊙ which fills its Roche lobe, in agreement with Kopal and Shapley (1956) results, Kopal (1959), or Sahade's (1963) results. From a consideration of the possible evolution of this system it is concluded that a large fraction of the original mass of the secondary is lost from the system. A study of the period changes indicates the possible presence of a third component of mass of about 0.5 M⊙ which is most likely to be an M dwarf.
Giant Equatorial Radio Telescope
Authors: Swarup G. , Hidayat B. , Sukumar S. 
Published: July 2016

AbstractA giant radio telescope for observing galactic and extragalactic radio sources at metre wavelengths is proposed. By locating a parabolic cylindrical antenna at a site close to the Equator such that its axis lies parallel to earth's axis, it is possible to construct a large collecting area economically. The proposed instrument will be very powerful for studying compact and diffuse features of radio sources, monitoring their variability, recombination and deuterium line work, studies of interplanetary medium and pulsar search.
Summary on Orientations of Rotation Axes
Authors: Vesely Carl D. 
Published: July 2016

To evaluate the precision of the previously determined coordinates of the rotation axes (table I) we should review the methods (originally developed for 433 Eros) and logic of the various authors. Table II contains pole coordinates of Eros and the sources of these data. A critical summary of the work will enable us to make some conclusions concerning the poles presented.There is general agreement that greatest rotational amplitude is observed when an asteroid is viewed equatorially, and we can detect three approaches to the determination of the Eros pole: the micrometer position angles observed by van den Bos and Finsen (1931); the graphic presentations used by Watson (1937), Stobbe (1940), and Rosenhagen (1932); and the mathematical model developed by Krug and Schrutka-Rechtenstamm (1936). These initial attempts yielded only approximate values, but the approximations were sometimes refined by analytical methods.
Are Meteors a Tool for Studying the Asteroids? Or Vice Versa?
Authors: McCrosky R.E. 
Published: July 2016

The bulk of the comments I made at the colloquium are to be found in two recent papers (McCrosky and Ceplecha, 1970; McCrosky et al., 1971). The following summary is offered in place of a full text.Most interpretations of all meteor data rely on knowledge of the relationship (luminous efficiency) between mass and luminosity. Discussions of recent experiments made to determine the luminous efficiency are found in papers by Ayers et al. (1970) and Becker and Friichtenicht (1971). Faint meteor phenomena can be understood if the meteoroids are weak, low-density (pm ≈ 0.25 g/cm3) “fluff balls” such as can be expected on the basis of Whipple's comet model (Jacchia, 1955; Jacchia et al., 1967). Alternative explanations, not requiring low densities, have been offered. Jones and Kaiser (1966) propose thermal shock of strong, high-density material as a fragmentation mechanism. Allen and Baldwin (1967) and Baldwin and Allen (1968) have reanalyzed Jacchia's data in terms of phenomena observed in the laboratory in simulated reentry experiments. Here, a high-density meteoroid froths and thereafter behaves as a low-density body. They also revise the luminosity law to account for blackbody radiation of refractory material. McCrosky and Ceplecha (1970) show that neither of these alternative explanations can apply to large bodies and, using photographic observations of bright fireballs, they defend Jacchia's original proposal for all meteors.
The Martian Satellites
Authors: Singer S. Fred 
Published: July 2016

The Martian satellites are some of the most interesting and accessible objects in the solar system, and therefore worth studying or even visiting. As small bodies, on the order of kilometers in diameter (see table I), they may have experienced no internal heating or volcanism, and could therefore be original condensations in the solar system. They may thus be the only remnants of the original planetesimals.An additional point of interest is that they are the only satellites in the inner part of the solar system–Earth's Moon is generally assumed to be a sister planet. As such, their study could illuminate one of the important differences between the inner and outer parts of the solar system.
Spectroscopy of Laboratory Plasmas
Authors: Burgess D. D. 
Published: July 2016

AbstractWork under the heading of Laboratory Plasma Spectroscopy may be conveniently separated into three classes depending on the extent to which the interaction of the emitting atoms with their plasma environment is central to the investigation. Zero order, the longest established use of laboratory plasmas in connection with astrophysics, concerns the use of hot plasmas for the excitation, measurement, and identification of the spectra of highly-stripped ions. In such work the properties of the plasma itself are usually of secondary importance. In first-order, plasma spectroscopy is used to determine fundamental atomic data concerned with the interaction of an atom with a single particle, usually either a photon or an electron, i.e.: the determination of oscillator strengths and collision cross-sections. Finally, higher-order processes in which the plasma nature of the surrounding medium is most relevant concern the study of line-shapes, and related topics such as the excitation of satellite spectral features by plasma oscillations. Developments in plasma diagnostic techniques in the last five years have greatly extended the scope of the second and third categories and have yielded much astrophysically important information from laboratory studies. Recent advances in these areas are reviewed.
Recent Spectroscopy of X-Ray Sources and Systems Related to Cataclysmic Variables: II
Authors: Crampton D. , Cowley A.P. , Hutchings J.B. 
Published: July 2016

ABSTRACTSpectroscopic observations of two very different objects are discussed: the first, SS433, is a wery massive binary system probably containing an unseen 0 or WR star and a black hole surrounded by a luminous precessing accretion disk (from which emanate spectacular relativistic jets); the second, GK Per, is a classical old nova consisting of a slightly evolved K2 star and an unseen white dwarf companion surrounded by an accretion disk which is less luminous than the K2 star.
On Evolutionary Models for SNI Progenitor Stars
Authors: Colvin Jeffrey D. 
Published: July 2016

ABSTRACTIt has been proposed that the Type I supernova (SNI) explosion starts in a white dwarf (WD) star that is accreting mass from a companion star in a close binary orbit. Others’ computations have described this explosion, but how an accreting WD can ever become an SNI if it first ejects the accreted envelope in one or more nova outbursts is still unresolved. My calculations of WD evolution include the effects of mass accretion, convective mixing, nuclear burning, and gravitational settling. These calculations test the Starrfield, Truran, and Sparks (1981) proposal that at low accretion rates, settling of the CNO nuclei will lead to steady-state hydrogen burning, not nova outburst. The preliminary results of this study, consisting of two evolutionary sequences of an initially cool pure 12C 1.0 Mʘ WD show that nearly half of the carbon near the base of the accreted layer, initially of solar composition, gravitationally diffuses out in 2 x 105 years.
Spin-Up and Magnetic Fields in DQ Her Stars
Authors: Lamb D. Q. , Patterson J. 
Published: July 2016

ABSTRACTWe have carried out a detailed comparison of the spin-up behavior of the recently discovered faint long-period X-ray sources, using the accretion torque theory of Ghosh and Lamb. We confirm that these sources are degenerate dwarfs. We find that they have magnetic fields B ~ 1 x 106 G, an order of magnitude smaller than those of AM Her stars. On this basis, we predict that they will show significant polarization in the infrared.
Polarimetric Observations of Hydrogen Deficient Stars
Authors: Raveendran A.V. , Rao N. Kameswara , Deshpande M.R. , Joshi U.C. , Kulshrestha A.K. 
Published: July 2016

AbstractPolarimetric observations of HD 30353, SU Tau, XX Cam, R Cr B,UV Cas, BD+13 3224,BD+10 2179 and HD 124448 are presented. The linear polarization of HD 30353 is found to vary appreciably at Hα over time scale as short as one day. It is also found that SU Tau shows significant variation in polarisation even at light maximum.
Preliminary Analysis of the Broad He I Emission Lines in R CrB
Authors: Surendiranath R. , Rangarajan K.E. , Kameswara Rao N. 
Published: July 2016

Abstract:During light minimum phase, R CrB shows a broad emission line spectrum of He I including λ10830, λ7065, λ7281, λ3889, λ6678 and λ3188. But λ5876 is very weak. The observed intensity ratios of I(λ3889)/I(λ5876) and I(λ7065)/I(λ5876) were greater than 1. The anomalous intensities of these lines appear to be due to optical depth efects. Peliminary analysis is presented to derive the physical conditions of the emitting gas.
Spectral Variations of the Rapidly Oscillating Ap Star HD 60435
Authors: Matthews J.M. , Slawson R.W. , Wehlau W.H. 
Published: July 2016

AbstractThe peculiar F star HD 60435 exhibits broadband light oscillations of low amplitude with periods between 15 and 4 minutes. Photographic spectra obtained in January/February 1985 using the University of Toronto 0.6 m telescope on Las Campanas, Chile, reveal that the star also undergoes slow spectral variations like those observed in many Ap stars. The data further suggest that Sr II maximum may coincide with maximum amplitude of light oscillations. According to the oblique pulsator model (Kurtz 1982) for such variables, this implies that Sr II is concentrated near at least one of the magnetic poles of HD 60435.
Hydrogen Deficient Planetary Nebulae: Preliminary Results
Authors: Pottasch S.R. , Mampaso A. , Manchado A. , Menzies J. 
Published: July 2016

AbstractNew spectra of A78 and A58 at different positions in the nebulae are presented. An abundance gradient is found in A78, extending quite close to the center. Similarly the nebulous knot near the center of A58 has considerably higher heavy element abundances than the outer regions of this nebula. The ionization state is considerably lower in A58 than A78. In A78 most of the neon is in the form of Ne+3 and Ne+4, indicating that the standard ionization correction factor as used by Jacoby and Ford, is substantially in error. Finally, the very high infrared excesses found in this nebulae are discussed.
The Distribution of Fe, Cr and Si Over the Surface of Θ AUR
Authors: Khokhlova V.L. , Rice J.B. , Wehlau W.H. 
Published: July 2016

AbstractVery accurate spectroscopic line profiles have been obtained at various phases during the 3d.618 period of the magnetic variable Ap-star Θ Aur. These profiles were observed using a Reticon detector at the coudé focus of the 3.5 metre Canada-France-Hawaii telescope. The mapping of Si, Cr and Fe over the surface of the star was done by solving the Inverse Problem. Complex spotty structure has been revealed with the number of Fe spots found being as great as six. The distribution of Cr is found to be similar to Fe but with less detailed structure. Si is distributed quite differently from Fe and Cr. Discussion of the relationship of the magnetic field maximum phase and the light curve along with the maps of the distribution of elements suggests that the principal spots of Fe and Cr are in phase with the light variability but they are 90° out of phase with Si and the magnetic field variation. We are surprised by the Si variability seeming to be 90° out of phase with the light variability.
The Analysis of Chemical Composition of Am Star Atmospheres
Authors: Boyarchuk A.A. , Savanov I.S. 
Published: July 2016

AbstractThe Survey of principal physical characteristics of the atmospheres of Am stars has been carried out. The anomalies of chemical composition have been discussed. The deficiency in C, O, Mg, Ca, and Sc alongside the excesses of heavier-than-Ni elements, with respect to Fe has been pointed out. The hypothesis on the nature of the observed anomalies are briefly discussed.
Investigating Astronomy’s History
Authors: Sperling Norman 
Published: July 2016

AbstractAmateur astronomers play an important role in historical astronomy and publish a wide range of studies. They can participate nearly as well as professional astronomers since neither are professional historians or archaeologists. Amateurs often restore old instruments and facilities, discovering clues to their design, manufacture and use that would not be noticed by non-astronomical historians.Possible studies include histories of institutions and of astronomy in different countries, biographies, and evolution of ideas. Publications and manuscripts could be studied for matters of current and historical importance. Folklore (of all countries) should be recorded before it dies out, and the beliefs behind it examined. More study groups involving amateurs, professionals and others should be established.
Searching for Comets
Authors: Mayer Ben 
Published: July 2016

Methods of searching for comets, novae and other events using projection and video blink methods, and simple orientation aids were described. The methods are covered in the following references:
1.Liller, W., Mayer, B.: The Cambridge Astronomy Guide, Cambridge University Press, 19852.Mayer, B.: International Halley Seminar, Alden Biessen, Belgium, 1986 Oct.253.Mayer, B.: 20th ESLAB Symposium, “Exploration of Halley’s Comet”, Heidelberg, 1986 Oct.27-314.Mayer, B.: Mercury, (Journal of the Astronomical Society of the Pacific), 1987 July/August
Trying to Reduce Errors in Visual Estimates of Variable Star Magnitudes
Authors: Velasco E. , Velasco P. 
Published: July 2016

The light-curves of many variables, prepared from a large number of individual estimates by many different observers, have a lot of scatter, ranges greater than one magnitude being common, although it is generally accepted that the eye can detect differences of roughly 0.1 magnitude, at least for stars of moderate brightness. The question arises whether these gross discrepancies can be reduced. We think that this is possible if observers make better use of their observational capabilities.For certain types of variable stars, e.g. long-period ones, the lack of accuracy may often be balanced by the vast number of estimates available. But for other stars, especially those exhibiting small-amplitude fluctuations, this process of combining observations leads to broad light curves that completely hide any possible fluctuations. Variable-star observers are familiar with these problems, but it is desirable to try to improve the accuracy that can be obtained.
Wanted: An International Jovian-Satellite-Phenomenon Centre
Authors: Wieth-Knudsen Niels P. 
Published: July 2016

AbstractAmateur observations made since 1977 show that although the ephemerides for the satellites of Jupiter published by the Jet Propulsion Laboratory are more accurate than those in the Astronomical Almanac, there are still small deviations, which may increase with time. Observation of eclipses, transits and occultations, as well as of the mutual phenomena that occur at 6-yearly intervals can provide information for correction of the ephemerides. There appear to be three groups coordinating observations: 1) in Germany, started by P. Ahnert in the early 1960s and now under H.-J. Blasberg; 2) in the U.S.A., started by J. Ashbrook in 1976, and continued by J. Westfall of the ALPO; 3) in Australia and New Zealand, led by B. Loader. These groups appear to work independently, and it would greatly help research on this subject if there were an International Centre for collecting observations of the Jovian satellites – perhaps under the supervision of the IAU – whereby all observations made anywhere in the world would be available to anyone investigating the subject. Paris, where the predictions are calculated, might be a very suitable site for such a centre.
Excitation of Non-Radial Oscillations by Overstable Convection in Differentially Rotating Massive Main Sequence Stars
Authors: Lee Umin 
Published: July 2016

SummaryWe investigated overstable convective modes of differentially rotating massive main sequence stars. It is examined that the overstable convective modes in a rapidly rotating convective core may excite envelope non-radial oscillations by the resonance coupling between them. Let us denote by q the ratio of the angular velocity of the rapidly rotating core to that of the envelope. Then, it is found that as the ratio q increases, the order of the non-radial g modes resonantly coupled with the convective mode becomes lower, so that the excited g modes come to have shorter periods in an inertial frame. It is also found that when the separation of the frequencies of the consecutive envelope g modes is wider than the resonance width, there occurs the alternation between the strong and the weak resonances, i.e., the resonantly coupled mode becomes overstable or neutral according to the strength of the resonance.
A Sensitive Line Search in Circumstellar Envelopes
Authors: Nguyen-Q-Rieu  , Deguchi S. , Izumiura H. , Kaifu N. , Ohishi M. , Suzuki H. , Ukita N. 
Published: July 2016

AbstractA molecular line search in the range between 85 and 89 GHz has been performed in the circumstellar envelopes of 11 evolved stars. Emissions of 29SiO J=2−1,28SiO J=2−1, HCN J=1−0, H13CN J=1−0, HC5 N J=33−32, HCO+ J=1−0 transitions and other transitions of C2 H, C4 H, and C3 N have been observed in 11 stars. We have detected the ground state 29SiO J=2−1 maser in several stars. We have also detected HCN emission in VY CMa. A narrow H13CN spike feature near the central velocity has been found in the spectrum of CRL 2688.
The

V

-Stokes Parameter as a Manifestation of Envelope Activity for Cool, Bright, Evolved Stars
Authors: Holenstein B. D. , Koch R. H. , Pfeiffer R. J. 
Published: July 2016

At Pennsylvania’s Flower and Cook Observatory, instrumentation has been developed to measure simultaneously the four Stokes parameters of the filtered radiation field from a celestial source. The instrumental Q/U/V-parameters have been found to be very small and well-behaved. Thus far, the program has concentrated on cool bright giants and supergiants and on hot, evolving close binaries. A single season’s investigation of Alp Ori has already been reported (Holenstein 1987) and the present paper is a summary of current results for the cool, evolved program stars.For Psi1 Aur, V CVn, 6 Gem, 72 Leo and 119 Tau no V-signal at the level of 3σhas been detected from data from the 1986-1987 season. At the level of 0.0n%, unambiguous and variable V-signals have been detected for VV Cep, Mu Cep, Alp Her, Alp Ori, Bet Peg, and Alp Sco.
The initial/final mass relation for stellar evolution with mass loss
Authors: Weidemann Volker 
Published: July 2016

The relation between initial and final masses is discussed under consideration of changing theoretical concepts and new empirical data on masses of white dwarfs and nuclei of planetary nebulae. It is concluded that presently adopted schemes of evolution need revision, and that no universal relation exists.The strongest evidence for large amounts of mass loss during stellar evolution has been provided by the existence of white dwarfs – with masses typically of 0.6 m (m = M/Mʘ), much below the galactic turn-off masses – and by the phenomenon of planetary nebula production before a star descends into the white dwarf region.
Manifestation of the 160-min Solar Oscillations in Velocity and Brightness (Optical and Radio Observations)
Authors: Kotov V.A. , Severny A.B. , Tsap T.T. , Moiseev I.G. , Efanov V.A. , Nesterov N.S. 
Published: July 2016

AbstractAll evidence of the solar origin of 160-min period oscillations is collected, and the present state of observations of this oscillation in optical and radio-ranges is considered. The main results are summarized: (a) the 160-min oscillation was observed in 1981 as well as before, (b) an attempt to find a nonradial component with l = 2 has failed, (c) the intensity and circular polarization of radioemission show with statistical significance the presence of this 160-min periodicity.