bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute Spectrophotometry of Be Stars
Authors: Stiff T. , Jeffers S.
Published: June 2019

Absolute spectrophotometry data have been obtained for a sample of Be stars. These data were obtained with the York Observatory 60 cm telescope and vidicon spectrophotometer. The data have been corrected for differential atmospheric extinction, instrumental response, and interstellar extinction and calibrated in terms of absolute flux. Absolute Hα and Hβ fluxes have been determined.
Short-term Photometric Variability in Be Stars in the Far-Ultraviolet - A Preliminary Report
Authors: Polidan R. S. , Peters G. J.
Published: June 2019

In this paper we report preliminary results on the first search for short term photometric variations in the far-UV in Be stars. Results for mu Cen and 28 Cyg indicate no significant variations.
Rotationally-Enhanced Stellar Winds (Review Paper)
Authors: Marlborough J. M.
Published: June 2019

The rotationally-enhanced stellar wind model for Be stars represents one attempt to understand many of the phenomena related to Be stars in terms of a stellar wind distorted and perhaps also enhanced by rapid stellar rotation. This review will concentrate exclusively on this particular approach; the current status of other attempts to model the circumstellar envelopes (CE) of Be stars are described in other reviews in this volume. It is assumed that Be stars are single stars; if a member of a multiple system, the separation of all components from the Be star is assumed to be sufficiently large that interactions due to mass transfer from any companion to the Be star are negligible.
The Far UV Spectrum of the Binary System AX Mon
Authors: Danezis E.
Published: June 2019

AX Mon is early indicated in the literature as a double system (Merrill 1952). Cowley (1964) noted that the system consists of a rapidly rotating B3 star and a somewhat fainter K giant.

We describe in this paper the main features of the far UV spectrum of HD 45910 observed with IUE at phase 0.5 (SWP 4762, LWR 4131). An analysis of this spectrum has been presented as part of a Ph.D. thesis (Danezis 1983). The far UV spectrum of AX Mon presents a large range of ionization stages going from CI, 01, NI, Mgl to SiIV, CIV, NV.
Reflections on Be Stars and the Be Phenomenon
Authors: Plavec Mirek J.
Published: June 2019

After three specialized meetings on Be stars, it: appears that the Be phenomenon is more complicated than we have thought. Five fundamentally different models are now competing. All five are actually based on an assumption that the Be stars are only a specialized (perhaps more easily noticeable) case of a more general phenomenon. Carefully arranged observations may decide between competing concepts, for example between spheroidal and disk-shaped circumstellar envelopes, and they can decide on the location of the cool strata (emitting Balmer lines) and hot strata (N V, C IV, Si IV). Eclipsing interacting binaries provide valuable clues.
The Calibration of Colours and Luminosities for Classical Cepheid Variables
Authors: Turner D. G.
Published: June 2019

Current progress is described for an ongoing program to secure new observational data (star counts, photoelectric, photographic & CCD photometry, and spectroscopy) for stars in the large sample of potential Cepheid calibrating clusters and associations.
An Optical P – L Relation for LPVs
Authors: Pierce M.J. , Crabtree D.R.
Published: June 2019

Supergiant Long-Period Variables (LPVs) are both more luminous and more common than Cepheids. The fact that a P – L relation exists at K (e.g. Wood et al. 1983 ApJ, 272, 99; Mould et al. 1990 ApJ, 349, 503) and not at visible wavelengths is usually attributed to the strong temperature sensitivity of TiO, which dominates the spectra of these stars in the visible. This has led us to apply a narrow bandpass (λ0 = 8250Å, BW = 350Å), avoiding TiO, in the hopes that an optical P – L relation can be found.

The data for Per OB1, the LMC, and M 33 are shown in figure 1. The small dispersion (σLMC = 0.22 mag.) and flat slope are evident. Combining the data we find:

(1)

with the absolute calibration from the ten LPVs in Per OBI, assuming m – M = 11.8±0.2 (Garmany & Stencel 1992 AAS, 94, 211).
Seismology of Pulsating Ap Stars: Results From The Past Decade, Prospects For The Next
Authors: Matthews Jaymie M.
Published: June 2019

Since the discovery of the first rapidly oscillating Ap (roAp) star in 1978 by Kurtz, this class of magnetic chemically-peculiar pulsators has grown to over two dozen. The eigenfrequency spectra of roAp stars (with periods of ∼ 6 – 15 min) are consistent with nonradialp-modes of low degreeand high overtonen, not unlike the Sun's five-minute oscillations seen in integrated light. However, unlike the Sun, the strong global dipole fields of roAp stars significantly affect the pulsations.

Although much of the effort in the last decade has been towards detecting new roAp candidates and refining the frequencies of known variables, initial “seismic” analyses have already yielded important results. Measurements of fundamental frequency spacingsconstrain the luminosities and radii of some roAp stars. In addition, mode splitting provides: (1) an independent determination of rotation period, even in the absence of longer-term light variations; (2) limits on the rotational inclinationiand magnetic obliquityβ; and (3) an indication of the relativeinternalfield strengths of certain roAp stars. Very recently, the temperature - optical depth structure of the atmosphere of HR 3831 was inferred from optical and IR photometry of its oscillations.

Judging from current developments, the next decade promises exciting results on both observational and theoretical fronts. Several roAp stars have now been monitored for over a decade, allowing us to investigate long-term period changes due to evolution, binarity, etc. Eigenfrequency models for stars in the mass and radius range appropriate for Ap stars are becoming available, as well as explicit treatments of the perturbations due to magnetic fields. Armed with these, we may be able to place some roAp stars on a theoretical(or “asteroseismological H-R“) diagram to derive independently their masses and main-sequence ages.
Comparative Pulsation Calculations with OP and OPAL Opacities
Authors: Kanbur S.M. , Simon N.R.
Published: June 2019

The OPAL opacities (Iglesias and Rogers 1991; Iglesias, Rogers and Wilson 1992) are recent revisions to the traditional Los Alamos (LA) opacities and have proven very successful in resolving the Cepheid beat mass, and to a lesser extent, the Cepheid bump mass discrepancies (Moskalik, Buchler and Marom 1991, hereafter MBM). MBM showed that for the beat Cepheids the P1/P0 period ratios, calculated with OPAL, yielded solar masses between 4 and 7, in agreement with other mass determinations. MBM also found that the P2/P0 period ratios were reduced, implying higher bump Cepheid masses, though the conflict with standard evolutionary masses was not completely eliminated. We have made linear nonadiabatic pulsation calculations with another set of recently computed opacities, namely those of the Opacity Project (Seaton 1987, 1992, hereafter OP). Since the two teams have employed different techniques in their calculations, it is of interest to compare pulsation results using the two sets of opacities.
Radiation Hydrodynamics in Pulsating Stars
Authors: Feuchtinger Michael U. , Dorfi E. A.
Published: June 2019

We present nonlinear radiation hydrodynamical calculations of Cepheid envelopes carried out using the method described in Dorfi & Feuchtinger (1991, A&A 249, 414). The radiative transport is treated within the grey Eddington approximation and all equations are discretised in conservative form on an adaptive mesh which is solved simultaneously with the physical equations. The resulting system of nonlinear algebraic equations is solved implicitly to avoid the restrictive Courant-Friedrichs-Lewy time step condition. In order to treat schock waves we use the artificial tensor viscosity developed by Tscharnuter & Winkler (1979, Comp.Phys.Comm. 18, 171) which is suitable for spherically symmetric problems. For the opacity we employ the latest OPAL tables (Rogers and Iglesias, 1992, ApJ, submitted); the equation of state corresponds to the standard evolution calculations according to Baker & Kippenhahn (1962, Zeitschr. f. Astrophys. 54,114).

We start from an initial hydrostatic model whose parameters correspond to a typical Cepheid (5 M⊙, 3000 L⊙, 5600 K). The subsequent dynamical evolution is initiated by the excitation of oscillations at the ionization zones in the stellar atmosphere where the opacity changes by several orders of magnitude. After an initial relaxation caused by discretisation errors and numerical noise, a periodic pulsation develops. Each pulsation is accompanied by a shock wave which propagates through the stellar atmosphere. A typical pulsation cycle is covered by about 70 time steps and the obtained periods lie in the range of 1 to 40 days.

We discuss in detail the excitation of the oscillations and the structure of the model during a pulsation cycle.
The Periods of X Cyg, T Mon, Y Oph, S Vul and SV Vul
Authors: Heiser A. M.
Published: June 2019

Photoelectric BV observations have been obtained with the 16-inch Vanderbilt APT over a number of recent years for five Cepheids. These data are being examined for periods, period changes, and for possible variations in the seasonal light curves.
Spectrophotometry determination of Teff's for six Cepheids with P < 4 d
Authors: Antonello E. , Fossati S. , Mantegazza L.
Published: June 2019

The population I Cepheids with 1.8 < P < 7 d are a non-homogeneous group in the sense that in this period range one can find fundamental, first overtone and double-mode pulsators. This implies that these three types of stars fall approximately in the same luminosity range. The knowledge of accurate physical parameters of these stars is therefore of paramount relevance in order to detect possible significant differences among different mode pulsators.

We have made spectrophotometric observations at La Silla Observatory of six Cepheids with P < 4 d (3 first-overtone and 3 fundamental mode pulsators). From a comparison with Kurucz's models of atmospheres (1979) we have derived their Teff's during the pulsational cycle. Due to the relevance of a correct estimate of the interstellar reddening in order to obtain accurate temperatures, we have independently determined the colour excesses of the studied objects by means of observations in the uvbyβ system using the method proposed by Feltz and McNamara (1980).
Extremely Low Amplitude Cepheids
Authors: Paul Butler R.
Published: June 2019

Several photometric studies conducted in the 1970's indicate that at least half the stars in the Cepheid instability strip are stable at the level of 0.02 mag (Fernie & Hube 1971; Percy 1975; Fernie 1976; Percy, Baskerville, & Trevorrow 1979). A precision radial velocity survey of these “stable stars” is currently being conducted by the author. Radial velocity errors have been reduced to a few tens of meters per second with the use of an iodine absorption cell (Marcy & Butler 1992).

Extremely low amplitude (200 m/s) periodic radial velocity variations have been found for HR 7796, an F8Ib supergiant (Butler 1992). Two and a half complete cycles have been monitored over three observing runs. The period is found to be 11.87 days. Observations of the reference star HR 509 (G8 V) taken on the same nights, show no periodicities and a scatter of just 20 m/s. Both the period and the shape of the velocity curve appear similar to a normal F8Ib Cepheid. If HR 7796 is a Cepheid, it is the smallest amplitude Cepheid by more than an order of magnitude.
The Blazhko Effect in RR Lyrae
Authors: Teays Terry J.
Published: June 2019

The cause of the Blazhko effect, the long-term modulation of the light and radial velocity curves of some RR Lyr stars, is still not understood. The observational characteristics of the Blazhko effect are discussed in §1. Some preliminary results are presented from aomw recent of campaigns to observe RR Lyr, using the International Ultraviolet Explorer along with ground-based spectroscopy and photometry, throughout a pulsation cycle, at a variety of Blazhko phases. A set of ultraviolet light curves have been generated from low dispersion IUE spectra. In addition, the (visual) light curves from IUE's Fine Error Sensor are analyzed using the Fourier decomposition technique. The values of the parameters ϕ21 and R21 at different Blazhko phasas of RR Lyr span the range of values found for non-Blazhko variables of similar period.
Graphite Grains and Graphite-Core-Ice-Mantle Grains
Authors: Wickramasinghe N. C.
Published: June 2019

Among the First Requirements for a Grain Model is that it should explain the observed interstellar extinction law or laws as they are now understood; a desirable feature of such a model is that as few ad hoc assumptions be made as possible.

A criticism of the classical ice grain theory is that a very narrow range of grain sizes (or a size distribution with a size parameter specified to within a few percent) must be postulated in order to obtain a fit with the mean extinction law. (See refs. 1 and 2.) While it is true that regional variations in the extinction law have recently been detected (refs. 3 and 4), the best available evidence indicates that the extinction law is quite uniform when averaged over individual large regions which are widely distributed in the galaxy. (See ref. 5 and paper by Nandy in the present compilation.) The restriction of particle size to a radius within a few percent of an arbitrarily specified value (r ≈ 3 X 10-5 cm) demanded on the basis of pure ice absorption is therefore considered quite unsatis-factory, particularly in view of the fact that no characteristic size parameter emerges from the Oort-van de Hulst theory for the formation and destruction of grains. (See ref. 6.)
Nucleation and Grain Growth in Interstellar Space
Authors: Donn Bertram
Published: June 2019

The First Detailed Studies to determine the processes by which interstellar grains may form were made by a group of Dutch astronomers in the 1940's. (See refs. 1 to 5.) Since that time very little systematic work on this problem has been done until very recently when Hoyle and Wickramasinghe (ref. 6) investigated graphite formation in cool stellar atmospheres. Van de Hulst's paper in 1949 (ref. 5) represents the culmination of an intensive attack which had considerable influence on astronomical thought about interstellar grains.

Somewhat ironically, beginning about 1949 many significant advances in physics and chemistry having a direct bearing on this problem were made. In 1949, Frank in reference 7 presented a theory which explained how real crystals tend to grow, and much work, both theoretical and experimental, has been done since then. (See ref. 8.) Recent extensive research in chemical reactions at low temperatures both in solids and on surfaces is reported in reference 9.
Interstellar Dust and the H2 Molecule
Authors: Schmidt K. H.
Published: June 2019

Nearly 20 Years Ago van de Hulst stated that the formation of molecular hydrogen occurs on the surfaces of the interstellar grains. (See ref. 1.) In the last years several authors discussed the problem of the interstellar abundance of the H2 molecule. (See refs. 2 to 9.) They all found that the percentage of the molecular hydrogen in the interstellar gas probably is much larger than had been thought in the past and that the essential mechanism of H2 formation is the formation on the particle surfaces. Therefore, the formation rate of interstellar H2 is a function of the area of the grain surface per unit volume, which is dependent on the average radius of the grains ā, on the number of dust particles per unit volume N(ā), and on the distribution function of the particle radii. The formation rate is determined by the density of the atomic hydrogen nH and the temperature of the interstellar gas Tgas. Finally, the formation rate of H2 depends on the probability π that an impinging hydrogen atom on a grain joins with another hydrogen atom to form a molecule.
A Review of the Achievements and Potential of Intensity Interferometry
Authors: Hanbury Brown R.
Published: June 2019

The stellar intensity interferometer at Narrabri Observatory was operated for ten years. Measurements were made of 32 single stars of spectral type 0 to F and were used to establish the first completely empirical temperature scale for hot stars. The application of a high-resolution interferometer to stellar astronomy was explored: observations were made of binary, rotating and emission-line stars, limb-darkening, polarized light and of the effects of atmospheric scintillation and of Cerenkov radiation from the night sky. This programme was completed in 1973. An analysis has been made of the astronomical programme and value to stellar astronomy of a much larger and more sensitive instrument. An intensity interferometer capable of reaching stars of magnitude +7.3 with a baseline of 2 km has been designed and its cost has been estimated.
Incoherent Infrared Spatial Interferometry
Authors: Low Frank J
Published: June 2019

By adapting the principles of interferometry first developed by Michelson, we have built a simple incoherent interferometer which operates efficiently from 2 to 20 microns

The design and performance of this instrument will be discussed More than 12 stars have been at least partially resolved at one or more wavelengths and, in several cases, their sizes and shapes have been determined A number of objects in the solar system have also been studied and useful studies of extragalactic nuclei are now possible. With the development of the new Multiple Mirror Telescope both the resolution and the sensitivity of this instrument will soon be extended.
Optimum Exposure Time And Filter Bandwidth In Speckle Interferometry
Authors: Walker J.G.
Published: June 2019

The dependence of the signal to noise ratio on the exposure parameters in speckle interferometry is analysed. The choice of the optimum exposure parameters, which are found to depend on certain statistical functions of the image intensity, is discussed. Preliminary results of measurements of these statistical functions are given.
The L-Shell Spectroscopy of Heavy Elements in Laser Produced Plasmas
Authors: Hamilton P.J. , Key M.H. , Lewis C.L.S. , Lunney J.A. , Thareja R.K. , Hutcheon R.J.
Published: June 2019

The L-shell spectra of heavy elements from germanium to molybdenum have been observed in plasmas generated by high power neodymium lasers at Queens University, Belfast and the Central Laser Facility (Rutherford Laboratory).

The spectra were recorded with convex crystal spectrometers with either a mica crystal (radius of curvature 3.81 cm) or a PET crystal (radius of curvature 15 cm). The spectral resolution is 1 in 1000. The spectra show lines from neon-like ions and associated satellites, fluorine-like ions, hydrogen and helium-like ion wavelength calibration lines and satellites from the latter. These will be discussed and some identifications given.
Temperature and Optical Depth Dependence of 0 VII Line Ratios with Reference to Solar Coronal Observations
Authors: Acton L.W. , Brown W.A. , Strong K.T. , Catura R.C.
Published: June 2019

The intensity ratio of the sum of forbidden (3S - 1S) and intersystem (3S - 1S) lines to the resonance (1P - 1S) line of helium-like ions can serve as a useful measure of optical depth due to resonance scattering. The temperature dependence of this ratio for a low density, optically thin plasma, is examined in detail for the case of 0 VII. Collisional excitation rates with exchange contributions as well as cascades and the effect of unresolved satellite lines resulting from dielectronic recombination are included. These results are compared to spatially resolved measurements of the solar 0 VII spectrum and the difference interpreted in terms of resonance scattering into or out of the line of sight.
Introductory Remarks on Spectroscopic Parameters
Authors: Abt Helmut A.
Published: June 2019

I hope that you will excuse a relative newcomer to this field and a spectroscopist for presenting his views, which may be somewhat different than those of others. I would like to enumerate the aims of research on visual systems and the needs of the field, particularly for spectroscopic data, as I see them.

I. Aims of Multiple-Star Astronomy. (1). Statistics of multiple systems. We would like to know the fraction of stars that are visually double, triple, etc. and in each case as a function of spectral type. For instance, is the frequency of visual doubles the same for Population II stars as for Population I stars? Or are the frequencies of visual doubles the same for stars off the main sequence as for their antecedents on the main sequence? For such information a negative result on duplicity is as important as a positive result, i.e. we wish to know which stars are not seen to be visually double as well as which ones are seen as doubles.
A Self-Consistent Model Atmosphere Program with Applications to Solar 0I Resonance Lines
Authors: Athay R. Grant , Canfield Richard C.
Published: June 2019

Profiles and total intensities are computed for solar 01 resonance lines at λ1302 and λ1305 using a model atmosphere program that includes non-LTE effects in both hydrogen and oxygen and that includes microturbulence both as a line broadening mechanism and as a contribution to the gas pressure. Good agreement is obtained between computed and observed intensities. The computed profiles appear to have too much 'self-reversal.
What Should We Do to Know More About Chromospheres and Coronae of Stars?
Authors: Thomas Richard N.
Published: June 2019

Chromospheres-coronas satisfy the last two of the proposed classification schemes: inadequacy of the classical atmosphere (CA) model to represent observations and a priori rejection of the CA model So we survey the question of what is required for more knowledge from the standpoint of asking what conceptual modifications will increase knowledge and what new observations are required. We stress that continued progress requires a continual interchange of ideas between the solar situation and the range of stellar situations.
Observations of ζ Aurigae Stars and Their Interpretation
Authors: Groth H. G.
Published: June 2019

A summary of information on the extended atmosphere of the K component coming from three eclipsing binaries consisting of a K supergiant and a main sequence B star. Various anomalies exist: (1) Discrepancy between electron density and metallic density inferred from observations, noting that the electrons should come from the metals. This suggests a cloud structure in the atmosphere. (2) Anomalous excitation temperatures and populations of the second quantum level of hydrogen suggests a solar-chromosphere type behavior for these K atmospheres. (3) Significant changes in the profiles of the Ca+ lines from one eclipse to another. The necessity to distinguish between effects coming from radiation of the B star on the K atmosphere and chromosphericlike effects is emphasized.
Microquasars and ULXS: Fossils of GRB Sources
Authors: Mirabell I. F.
Published: June 2019

Gamma-ray bursts (GRBs) of long duration probably result from the core-collapse of massive stars in binary systems. After the collapse of the primary star the binary system may remain bound leaving a microquasar or ULX source as remnant. In this context, microquasars and ULXs are fossils of GRB sources and should contain physical and astrophysical clues on their GRB-source progenitors. Here I show that the identification of the birth place of microquasars can provide constrains on the progenitor stars of compact objects, and that the runaway velocity can be used to constrain the energy in the explosion of massive stars that leave neutron stars and black holes. The observations show that the neutron star binaries LS 5039, LSI +61°303 and the low-mass black hole GRO J1655-40 formed in energetic supernova explosions, whereas the black holes of larger masses (M ≥ 10 M⊙) in Cygnus X-l and GRS 1915+105 formed promptly, in the dark or in underluminous supornovao. The association with clusters of massive stars of the microquasar LSI +61°303 and the magnetars SGR 1806-20 and SGR 1900+14, suggest that very massive stars (M ≥ 50 M⊙) may -in some cases- leave neutron stars rather than black holes. The models of GRB sources of long duration have the same basic ingredients as microquasars and ULXs: compact objects with accretion disks and relativistic jets in binary systems. Therefore, the analogies between microquasars and AGN may be extended to the sources of GRBs.
Results of a Search for New Microquasars in the Galaxy
Authors: Ribó M. , Paredes J. M. , Martí J. , Casares J. , Bloom J. S. , Falco E. E. , Ros E. , Massi M.
Published: June 2019

We present here the results of a search for new microquasars at low galactic latitudes, based on a cross-identification between the ROSAT all sky Bright Source Catalog (RBSC) and the NRAO VLA Sky Survey (NVSS) and follow-up observations. The results obtained up to now suggest that persistent/silent microquasars such as LS 5039 are rare objects in our Galaxy, and indicate that future deeper surveys, and harder than the RBSC in X-rays, will play a fundamental role in order to discover them.
Symbiotic Stars in the Magellanic Clouds
Authors: Mikołajewska Joanna
Published: June 2019

Orbital periods and other parameters of symbiotic binary systems in the LMC and SMC are presented and discussed. In particular, the symbiotic stars in the MCs are compared with those in the Milky Way.
Revealing the Nature of the Highly Obscured Galactic Source IGR J16318-4848
Authors: Chaty S. , Filliatre P.
Published: June 2019

The X-ray source IGR J16318-4848 was the first source discovered by INTEGRAL on 2003, January 29. We carried out optical and near-infrared (NIR) observations at the European Southern Observatory (ESO La Silla) in the course of a Target of Opportunity (ToO) programme. We discovered the optical counterpart and confirmed an already proposed NIR candidate. NIR spectroscopy revealed a large amount of emission lines, including forbidden iron lines and P-Cygni profiles. The spectral energy distribution of the source points towards a high luminosity and a high temperature, with an absorption greater than the interstellar absorption, but two orders of magnitude lower than the X-ray absorption. We show that the source is an High Mass X-ray binary (HMXB) at a distance between ~ 1 and ~ 6 kpc, the mass donor being an early-type star, probably a sgB[e] star, surrounded by a rich and absorbing circumstellar material. This would make the second High Mass X-ray Binary (HMXB) with a sgB[e] star after CI Cam, indicating that a new class of strongly absorbed X-ray binaries is being unveiled by INTEGRAL.
Accretion Flows in Magnetic Cataclysmic Variables
Authors: Norton A. J. , Somerscales R. V. , Parker T. L. , Wynn G. A. , West R. G.
Published: June 2019

We present the results of simulations that explore the variety of accretion flows possible in magnetic cataclysmic variables (mCVs). Our simulations evolve to equilibrium periods spanning 0.01 < Рspin/Рorb < 0.6 and the resulting flows vary from disc-fed systems at Рspin/Рorb ~ 0.01 - 0.1, to stream fed systems at Рspin/Рorb ~ 0.1 - 0.5 and systems fed from a ring at the outer edge of the white dwarf's Roche lobe at Рspin/Рorb ~ 0.6.
A Strong Variation of Accretion Disc Corona Size with Luminosity in LMXB
Authors: Church M. J.
Published: June 2019

The controversy that has existed for many years over the nature of the continuum X-ray emission components in X-ray binaries is reviewed, in which workers have been polarized between the Eastern model with a small central Comptonizing region around the compact object and alternative models. We present measurements of the radial extent of the Comptonizing ADC in low mass X-ray binaries which rule out the Eastern model and show that, the ADC is extended (the Birmingham model). Dip ingress timing shows conclusively that the ADC radial extent varies from 7% of the accretion disc radius in faint sources, to 65% in bright sources. Remarkably, the size depends strongly on the source luminosity suggesting that the ADC is formed by irradiation of the disc by the neutron star and the hot inner disc. These results have fundamental implications for the correct description of Comptonization in X-ray binaries, and the spectral form is derived for the Comptonized emission of an extended ADC led by soft, seed photons from the underlying disc which differs substantially from that of the Eastern model. Measured ADC electron températures provide values of the Compton radius in broad agreement with measured values of the radial extent of the ADC. Finally, we show that the results are inconsistent with the non-thermal emission being produced in a jet, and so provide evidence against the recent suggestion that all LMXB have jets.
A Simple, Unifying Model of the Extreme Ultraviolet Spectra of Dwarf Novae in Outburst
Authors: Mauche Christopher W.
Published: June 2019

A simple model of the boundary layer and accretion disk wind of dwarf novae in outburst is briefly described and applied to the Chandra Low Energy Transmission Grating spectra of WZ Sge and SS Cyg in outburst.
Measuring the Mass Ratios of X-Ray Transients from the Rotational Broadening of the Secondary Star's Spectrum
Authors: Robinson Edward L. , Bitner Martin
Published: June 2019

We describe a new computer program for calculating the spectra of stars that fill their Roche lobes in close binary stars.

Soft X-ray Transients (SXTs) are interacting binary stars in which a compact star is stripping mass from a relatively-normal companion star (the secondary star). One step in the usual method for measuring the mass of the compact stars in these systems is to determine the mass ratio from the rotational broadening of the absorption lines in the spectrum of the secondary. With a few outstanding exceptions (e.g., Shahbaz 2003), the observations have typically been analyzed assuming that the observed spectrum can be modeled by convolving the spectrum of a non-rotating star with a line-broadening function appropriate for a rotating, spherical star. The results are often inadequate because 1) the profiles of the absorption lines vary strongly with orbital phase, and 2) the limb darkening differs from line to line so that no single broadening function can represent the behavior of all lines.
Using High Resolution Data to Investigate the Variability of GG Carinae System
Authors: Machado Maria Auxiliadora , Araújo Francisco Xavier de , Lopes Dalton de Faria , Pereira Claudio Bastos
Published: June 2019

GG Carinae is a peculiar emission line object classified as a B[e] star. Using high resolution data we confirm that GG Carinae is at same time a binary system and a variable star.

GG Carinae was classified by Lamers et al. (1998) as a B[e] star and also is pointed out as a binary system. So, any investigation to determine its parameters requires an detailed analysis in order to know and to separate the effects of each component. Gosset et al. (1984) used Fourrier Analysis in the data obtained from photoeletric photometry of both the standard UBV and Strongren system and calculated a period of 31D.02.
Determining the Masses and Evolution of CVs through Ellipsoidal Variations
Authors: Osborne Heather L. , Harrison Thomas E. , Johnson Joni J. , Howell Steve B.
Published: June 2019

We use simultaneous multi-wavelength BVRI-JHK photometric observations of cataclysmic variables (CVs) to determine the inclination angles of the systems, together with phase-resolved spectroscopy to calculate the K2 and vsini. We then calculate the masses of the system components. We are using these data to construct mass-radius diagrams of the secondaries in an effort to resolve some of the debate over their evolutionary history.
A VLA Survey of Magnetic Cataclysmic Variable Stars
Authors: Gray Сandace , Mason Paul A.
Published: June 2019

Cataclysmic Variables (CVs) are close binaries containing a white dwarf primary and a Rochelobe filling red dwarf secondary. In magnetic CVs (MCVs) the white dwarfs have magnetic fields that are sufficiently strong (106 – 108 Gauss) to direct the accretion flow onto the surface of the primary. MCVs are divided into the lower field intermediate polars (IPs) and the higher field polars. Typically, IPs have accretion disks that are disrupted in the center and magnetically channelled flow onto the poles. Polars are diskless, an accretion stream flowing from the inner Lagrangian point impacts directly onto one or both magnetic poles. In addition, polars tend to have white dwarfs which rotate in synchronism with the binary orbit, while IPs have white dwarfs which rotate faster than the binary period. There are a few rare exceptions to this characterization, such as the slightly asynchronous polars and the stream-fed IPs.
Clementine Photographs of the Inner Zodiacal Light
Authors: Cooper B. L. , Zook H. A. , Potter A. E.
Published: June 2019

Over 700 photographs of the inner zodiacal light were taken from the Clementine spacecraft while it was in orbit around the Moon. These exposures were taken with the 28° x 43° field-of-view Star Tracker camera and the 4.2° x 5.6° field-of-view UV/Vis camera. The images were made while the Clementine spacecraft was on the dark side of the Moon such that the Sun was occulted. Most of the photos were taken at the highest possible sensitivity and longest exposure time (0.7 sec) in order to detect an expected weak lunar horizon glow. Consequently, many of the photos are over exposed where the zodiacal light is the brightest. However, a subset of photos were purposefully taken with a range of exposure times to reveal the entire inner zodiacal light structure, both in latitude and longitude, to within 1° of the Sun. These Star Tracker images show the lenticular shape of the inner zodiacal light. When work to correct the images to absolute photometry is concluded, the detailed structure of the entire inner zodiacal light will be derived.
Understanding vocabulary acquisition, instruction, and assessment: A research agenda
Authors: Schmitt Norbert
Published: June 2019

This paper suggests six areas of vocabulary research which the author believes would be fruitful for future research. They include (1) developing a practical model of vocabulary acquisition, (2) understanding how vocabulary knowledge develops from receptive to productive mastery, (3) getting lexical teaching/learning principles into vocabulary and language textbooks, (4) exploring extramural language exposure and how it can best facilitate vocabulary acquisition, (5) developing more informative measures of vocabulary knowledge, and (6) measuring fluency as part of vocabulary competence. Nine tasks are suggested for how to research these six research directions, with advice on research design and how to set about carrying out the tasks.
2.2 Dairy Herd Management
Authors: Esslemont R. J. , Stephens A. J. , Ellis P. R.
Published: June 2019

The Unit's work on herd monitoring was motivated by the need for a system to record data for a Study of Methods of Improving Oestrus Detection (Esslemont, 1973). These interests were shared with Dr R. S. Morris, then at Melbourne University, who made available a suite of computer programs for analyzing dairy herd health and fertility data which suited the immediate needs (Morris, Blood, Cannon, Cannon and Williamson, 1978). Out of this generous co-operation has evolved the ‘MELBREAD’ Herd Health and Fertility Reporting Scheme, the more comprehensive ‘DANDAIR’ system, the ‘YOUNGSTOCK’ system for recording heifers, and now ‘DAISY’ with which data processing is being decentralized to farms and veterinary practices. We are also starting to develop similar systems for intensive pig enterprises.

This paper presents background information on the development of herd monitoring and a description of computerized record systems for the dairy herd developed by VEERU, especially the ‘DAISY’ software package for small computer systems.

An estimate of the breakdown of fixed and variable costs on a per cow basis for a UK dairy herd is shown in Table 2.2.1a and typical good performance levels are shown in Table 2.2.1b. These figures show the need for very high technical performance in order to produce truly economic results. They also show that costs per cow for improved management information systems (at £5/cow/year) can be kept below 1% of turnover.
6.11 Copper Oxide Wire for the Bovine
Authors: MacPherson A.
Published: June 2019

A satisfactory method of copper (Cu) supplementation, particularly in the field situation, has yet to be found (MacPherson, 1983). Work in Australia (Dewey, 1977 and Deland, Cunningham, Milne and Dewey, 1979) has shown that orally administered copper oxide wire or ‘needles’ (CuON) remained in the lining of the abomasum of sheep and calves and gradually released Cu over a long period of time. This treatment was successfully tested on hill sheep in Scotland by Whitelaw, Armstrong, Evans, Fawcett, Russel and Suttle (1980). Suttle (1979) has also recorded that calf liver Cu concentrations were raised significantly by a single 50 g oral dose in a limited term (41 day) experiment. No reports have appeared of the usefulness of this treatment under field conditions for the bovine in this country. Three trials are described which examined the effectiveness of small oral doses of CuON on the Cu status of beef suckling calves, dairy heifers and beef suckler cows.
Donor policy on funding livestock research and development
Authors: Scott J. M.
Published: June 2019

In recent years there has been a decline in donor support for livestock research and production in the developing world. Evaluation studies suggest that such activities have a mixed record of success. Failures have been ascribed to institutional weaknesses and an inability to identify farmers’ priorities. In addition, there is an increasing donor concern about the adverse environmental effects of livestock, particularly in fragile ecosystems.

Concern has been expressed that, if the decreasing support is not reversed, donor supported activities will underplay the important rôle of livestock in rural development.

There are, however, signs that many of the lessons of experience have been learned and that there is an improving understanding of the crucial part played by livestock in sustainable land-use systems and in generating cash income.

Donors are increasingly appraising livestock activities within an agro-ecological or land-use systems framework and adopting a ‘demand-led’ approach based on farmer's priorities. Past experience suggests that Government institutions should concentrate on regulatory functions and other activities unsuited to the private sector. There is, therefore, a greater willingness to involve private-sector organizations, co-operatives and non-governmental organizations. Environmental impact assessments are becoming an integral part of donor supported rural development activities.

Any increase in the levels of funding for livestock research and development will depend on the socioeconomic and environmental impact of livestock in the developing world being better understood and, wherever possible, quantified.
Technical constraints to ruminant livestock production in sub-Saharan Africa
Authors: von Kaufmann R. R. , Fitzhugh H. A.
Published: June 2019

Constraints do not only occur in production systems. They also limit the support available from research and extension and they have serious consequences for human welfare in Africa and for the whole community of nations.

The agricultural research agendas in sub-Saharan Africa are indicating more concern for appropriate technology and interest in collaboration but support for research is declining when it is most urgently needed. Food production in sub-Saharan Africa is not keeping pace with demand and this is a cause of instability that will constrain all other attempts at development.

The effect of the constraints is most evident on the deteriorating environment which is evident in each agro-ecological zone despite the different potentials and pressures. Animal productivity is low but has the potential for substantial improvement. Misconceptions and a lack of faith in the potential for improvement are themselves constraints in the sense that they discourage donor support for research to alleviate the real problems. Opportunities for improvement have been identified in each agro-ecological zone.

There are three major categories of research institutions: national agricultural research systems, international agricultural research centres and developed country research centres. Each has its own comparative advantages and a vital rôle to play in collaboration with the others. With the limitation in research resources there is an urgent need to develop appropriate research methods and techniques that can be applied sufficiently to have impact across the whole of sub-Saharan Africa. These are particularly required in regard to food production. Research opportunities are identified in plant genotypes, animal health, animal genotypes and extension and input supply.
Antinutritional factors in foods for livestock
Authors: Makkar H. P. S.
Published: June 2019

Antinutritional factors in livestock foods may be defined as the substances which either by themselves, or through their metabolic products arising in the system, interfere with food utilization and affect the health and production of animals. These deleterious substances, also referred to as anti-quality factors can be divided tentatively into four groups based on their effects on livestock: (i) affecting protein utilization and depressing digestion (protease inhibitors, tannins, saponins, lectins, etc.), (ii) metal ion scavengers (oxalates, phytates, gossypol pigments, glucosinolates), (Hi) antivitamins, and (iv) those which cannot be put in the above categories (mycotoxins, mimosine, cyanogens, nitrates, alkaloids, photosensitizing agents, isoflavones, etc.). This paper discusses only those deleterious substances which are of prime concern to the farmers and scientists of developing countries. Much emphasis is given to polyphenols compounds, as this class of anti-nutritional factor is the most widespread in non-conventional foodstuffs, i.e. agroindustrial and forestry byproducts. The effective utilization of these non-conventional foods forms the main area of research in the third world countries due to shortages of conventional foods. Efforts have been made to present the current knowledge on their assay methods, effects on animals, mode of action and detoxification/detannification using physical, chemical and biotechnological approaches. Other anti-quality factors viz., mycotoxins, mimosine, cyanogens and nitrates which also cause damage to livestock in developing countries are also discussed briefly.
Use of the gas production technique to investigate the supplementation of nitrogen-deficient foods
Authors: Wood C. D. , Prathalingam N. S. , Murray A. M. , Matthewman R. W.
Published: June 2019

A major focus for improving the diets in many less developed countries (LDCS) is the provision of rumen fermentable nitrogen (N) using protein supplements to complement N-deficient foods. However, in vitro digestibility methods usually use N-rich environments for the degradation of single foods. This conventional approach may give data which do not reflect the nutritive value of the N-deficient diets often on offer in LDCS, neither is it appropriate for using in vitro gas production to study protein supplementation. Our earlier study indicated that, by using a N-free medium, the gas production technique responded to added ammonium sulphate and urea. The ADAS standardized methodology, which used 10 ml of inoculum instead of the 5 ml used in the earlier study, was found not to be very responsive to N supplementation. The ADAS methodology was therefore investigated in order to develop a modified protocol for fermenting foods in an N-limited environment. The study involved using inocula diluted to different extents in N-free medium for fermenting N-deficient substrates in N-free and N-rich media. The modified protocol was then used for investigating the interactions between N-rich and N-deficient foods from north-west India.
Concentrate foods: is all degraded organic matter fermented?
Authors: Fakhri S. , Moss A. R. , Givens D. I. , Owen E.
Published: June 2019

The in situ and in vitro techniques have been adopted to estimate the degradability of organic matter (OM) in the rumen on the basis that this provides an estimate of ATP for microbial protein synthesis. However this assumption may be incorrect since ATP production requires the fermentation of degraded carbohydrate and Beever (1993) has shown that some degraded hexose can be used synthetically without ATP production. In addition, degraded OM from protein is likely to produce less ATP than the same amount of degraded carbohydrate. The gas production (GP) technique measures end products of fermentation and may be a better guide to ATP production. On the assumption that the in situ and in vitro techniques provide satisfactory estimation of OM degradability, the work discussed here used the GP technique to estimate the effective unfermentable OM fraction of the degraded OM (EUFDOM) for a range of concentrate foods.
Standardizing near infrared reflectance spectra by detrending against a water spectrum, for calibrating the voluntary intake of barley straw by sheep
Authors: Goodchild A. V. , El Haramein F. J.
Published: June 2019

The moisture content of samples affects the accuracy of predictions made using near infrared reflectance spectroscopy (NIRS). One way to prevent the problem is to develop a repeatability file, which summarizes variation in the spectra of a single sample resulting from variation in conditions at the time of scanning (Murray, 1993). Another method is to re-read the spectra of all samples on a second occasion when their moisture content has been deliberately altered (Murray, 1993). The present study, using straws with known voluntary intakes, compares these methods with a simple technique that compensates the spectra for moisture content before NIRS calibration (or prediction) begins.
Regaining a high health status – light at the end of the tunnel
Authors: Mortimer I
Published: June 2019

The purpose of this paper is to summarise the various means available for eliminating/eradicating disease and the economic consequences. Success rates for various diseases are discussed and summarised. A specific UK example is given to illustrate the planning and work that is required, as well as the cash flow over a twelve-month period. A typical timetable of events for eradicating/eliminating endemic diseases present in the UK and Ireland is discussed, as is the potential for regional/national eradication.