bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of wind clumping on colliding winds
Authors: Lépine Sébastien
Published: June 2019

Recent studies of variable Wolf-Rayet emission lines reveal a hierarchy of structures, characterized by power laws analogous to what is expected from supersonic compressible turbulence. The collision of inhomogeneous winds can be very different from the case of smooth winds. The difference will mainly depend on two factors: (i) the relative importance of the inhomogeneous compared to the homogeneous component; and (ii) the characteristic filling factor of the inhomogeneous component. Using relations derived from observations of variable line structures (“blobs”), it can be deduced that the flux emitted by the inhomogeneous part of the wind of a WR star is dominated by its smallest structures. This implies that a significant fraction of the underlying emission line profile could be produced by small, undetectable inhomogeneities. It can also be deduced that the volume spanned by the inhomogeneities is dominated by the largest structures. This in turn implies that the filling factor should be low, or that we are dealing with a fractal-like hierarchy. It is suggested that the wind is composed of dense structures separated by large “voids” which may actually be filled by a homogeneous wind component. The interacting zone of two inhomogeneous colliding winds should thus be much more extended in space than for a smooth-wind model, because the dense, inhomogeneous structures are able to penetrate through the large “voids”.
The colliding wind-formed structures of supernova precursors
Authors: Tsiopa O. A.
Published: June 2019

The wind interaction processes in supernova precursors can be responsible for the formation of regular structures of the circumstellar matter not only at the distances of 1018 cm (SN1987A), but also at those of less than 1016 cm.
ASCA X-ray observations of the Wolf-Rayet stars HD 193793 and HD 93162
Authors: Skinner S. , Nagase F. , Koyama K. , Maeda Y. , Tsuboi Y.
Published: June 2019

The Japan-U.S. satellite ASCA was launched in February 1993 and provides a new capability to obtain high-resolution X-ray spectra of Wolf-Rayet stars in the 0.5 — 10 keV band. We present spectra of the wide binary HD 193793 (WC7+O4-5) obtained three months after periastron with the WC7 star in front, and of the WN7 star HD 93162 in Carina. The spectrum of HD 193793 is heavily absorbed below 2 keV by the WC7 wind and shows a prominent emission line from He-like iron at 6.7 keV. Acceptable fits were obtained using a Raymond-Smith model with kT ≈ 3 keV and non-solar abundances. In contrast, the spectrum of HD 93162 is softer and shows very little emission above ≍2 keV. The relatively low signal-to-noise precludes emission line analysis, and an acceptable spectral fit was obtained using a simple Bremsstrahlung model with kT ≍ 1.6 keV. No significant variability was detected in the X-ray light-curves of either star.
Colliding stellar winds: X-ray emission and instabilities
Authors: Stevens Ian R.
Published: June 2019

Colliding stellar winds are an important part of early-type binaries. In this paper I discuss the phenomenon, concentrating mainly on the basic hydrodynamics of colliding winds, and the physics of X-ray emission. The following topics are covered:

1) Basic physics: The basic characteristics of the shock-produced thermal X-ray emission, and discuss general trends of X-ray emission from colliding wind binaries (CWBs).

2) Hydrodynamic simulations: Recent calculations have found that the interface in colliding winds is usually dynamically unstable, with three distinct instabilities.

3) Gamma Velorum: recent ROSAT observations give much insight into colliding winds. I discuss recent hydrodynamic calculations pertaining to these observations.

4) Radiation Hydrodynamics in CWBs: Recent calculations have included the effects of both radiation fields on the wind hydrodynamics in colliding wind systems.
Instabilities in colliding winds
Authors: Walder Rolf , Folini Doris
Published: June 2019

The significance of radiative cooling for the stability properties of colliding astrophysical flows is shown. In the cases of WR ring nebula NGC 6888 and WR binary V444 Cyg it is found that thermal instabilities in the radiative loss function A(T) Tβ, β = β(T) not only have an influence on the dynamics of the collision zone, but also that they lead to a quasi-periodic increase of the radiated energy.
Cygnus X-3 an evolutionary missing link found?
Authors: van Kerkwijk M.H.
Published: June 2019

I review the properties of the X-ray source Cygnus X-3, and the evidence that is available that indicates that its companion is a Wolf-Rayet star. I focus on the interpretation of spectra of its infrared counterpart. Considering all data, I conclude that the companion is indeed a WR star, and I discuss the ramifications of this conclusion for our understanding of WR stars in general.
OeBe-stars with possible compact companions observed at X-rays
Authors: Meurs E.J.A. , Piters A.J.M.
Published: June 2019

A survey of bright O- and B-type stars has been conducted from the ROSAT All Sky Survey data, aiming at the detection of compact companions expected for Oe and Be stars. Concurrent Hα spectroscopy has been used to establish the level of activity of these stars around the time of the X-ray observations. The detection rate of OB and OeBe stars as well as their average X-ray over bolometric luminosities suggest little difference between these two groups of objects. Instead of accretion onto a compact object (NS, WD), the X-ray emission from OeBe stars may be produced by stellar winds as has been proposed for O- and early B-type stars in general. Flexibilities in the available models for X-ray emission from accreting WDs may allow the X-ray emission from such objects to remain below a detectable level. These investigations are now being extended to pointed observations in the ROSAT Archive.
Galaxy-Galaxy Lensing: Status & Applications
Authors: Brainerd Tereasa G.
Published: June 2019

There are now 10 independent observational investigations which have detected systematic weak gravitational lensing of background field galaxies by foreground field galaxies. This effect, known as galaxy-galaxy lensing, results in a very slight (of order 1%) distortion to the intrinsic image shapes of the lensed galaxies. Although small, the galaxy-galaxy lensing signal is coherent about the lens centers and is, therefore, detectable in large data sets via an ensemble average over many candidate pairs of lenses and sources. Here I summarize the results of the recent detections of galaxy-galaxy lensing and discuss some applications that are likely to be implemented in the very near future.
Gravitational Lensing by Elliptical Galaxies
Authors: Mortlock Daniel J. , Webster Rachel L.
Published: June 2019

The probability that high-redshift quasars are gravitationally-lensed by intervening galaxies increases rapidly with the cosmological constant, ΩΛ0 (whilst being only weakly dependent on the density parameter, Ωm0), and the low number of lenses observed implies that ΩΛ0 ≲ 0.7 (e.g. Kochanek 1996). One of many uncertainties has been the (small) core radii of elliptical galaxies, which, at least naively, reduce their lensing cross-section. However, if ellipticals are normalised relative to their observed line-of-sight velocity dispersion, σ||, then increasing the core radius must result in an increased mass normalisation (specified by the assymptotic velocity dispersion, σ∞).
The JVAS/CLASS 6″ to 15″ Lens Search
Authors: Phillips P. M. , Browne I. W. A. , Wilkinson P. N. , Jackson N. J. ,   members of the CLASS collaboration
Published: June 2019

We present the strategy and status of a gravitational lens search for multiple imaging with angular separations between 6″ and 15″ within the combined JVAS and CLASS dataset of ˜ 15000 flat-spectrum radio sources. Currently all but one lens candidate have been rejected.
Preliminary observations of water masers associated with IRAS4A and IRAS4B
Authors: Marvel Kevin B. , Claussen Mark , Wootten Alwyn
Published: June 2019

We present preliminary observations of water masers associated with IRAS4, a pair of young stellar objects in the NGC 1333 star forming region. The masers are quite strong and spatially distinct. Proper motion observations have been obtained from various epochs of observation typically separated by about three weeks. IRAS4A consists of two regions of maser activity separated by about 114 AU along a position angle of 138 degrees. Expansion of about 68 km/s is detected. IRAS4B consists of two linear emission regions separated by about 175 AU on a 150 degree position angle. The linear features are about 15 AU in length and about 2 AU thick. They are expanding away from each other at about 70 km/s.
A blind survey of the 6.7 GHz methanol maser line
Authors: Szymczak Marian , Kus Andrzej J. , Hrynek Grzegorz
Published: June 2019

A blind survey for 6.7GHz methanol maser emission has been made with the 32 m Toruń radio telescope. The survey consists of 4,800 spectra on an equilateral triangular grid pattern with each grid point separated by 4.4 covering a field of ∼21 deg2 at galactic longitudes 20° to 40° and galactic latitudes ±0°52. The average sensitivity was 1.6 Jy and the spectral resolution was 0.04kms−1. A total of 99 sources were detected, 28 of which were not found during previous searches of IRAS-selected ultracompact HII regions. The peak flux density of new detections is usually lower than 30 Jy. About half of the methanol masers have no IRAS counterparts within a radius of 2. The nature of these sources is unclear.
Influence of dust parameters on class II methanol maser pumping
Authors: Ostrovskii Andrei B. , Sobolev Andrej M.
Published: June 2019

Results of model calculations for class II methanol masers (MMII) are presented. The model of the pumping assumes that an external dust layer provides the source of energy for maser excitation. The dependence of the emergent maser spectrum on the properties of the dust layer is studied. These properties include the chemical composition and sizes of dust grains, the temperature and optical depth of the dust layer. as well as the dilution factor of external dust emission. It is shown that, in order to reproduce the observed patterns of class II methanol maser line ratios, the pumping dust layer should be mostly composed of silicate grains with sizes smaller than 0.01 μ. It is shown that the layer of warm (> 125 K) dust effectively pumps the strongest MMII transitions over a wide range of 30 μ dust opacities (0.01–2) and dilution factors (0.02–0.5).
Extragalactic H2O Masers
Authors: Greenhill Lincoln J.
Published: June 2019

Study of extragalactic H2O masers has progressed significantly in the 25 years since their discovery. Existing in star forming regions and in the accretion disks supermassive black holes, they are familiar and unfamiliar at the same time. A review of how our understanding has grown, up to the present day, is followed by comments on future prospects.
The Galactic System of Open Star Clusters: A Personal Perspective
Authors: L. Phelps Randy
Published: June 2019

Technology is now allowing for the investigation of star clusters outside of the Milky Way. As attention turns to the extragalactic star clusters, a perception that the system of star clusters in the Milky Way is well understood may grow, resulting in the neglect of these important objects. In this review, the status of our understanding of the Milky Way's open star cluster population will be discussed. Specifically, I will attempt to illustrate not only the important information that can and must be learned from these nearby star clusters, but also the degree to which our understanding of the Galactic open clusters remains incomplete.
HST Observations of 3 More Old LMC Clusters
Authors: A. Johnson Jennifer , Bolte Michael , Stetson Peter B. , Hesser James E.
Published: June 2019

We present color-magnitude diagrams (CMDs) based on HST F555W (“V”) and F814W (“I”) observations of three old LMC clusters: NGC 2210, NGC 1786, and Reticulum. The fiducial derived from the CMD of NGC 2257, another LMC cluster, provided a good fit to the data for the new clusters. Because NGC 2257 has a similar metallicity ([Fe/H]∼ −1.8) to NGC 2210, NGC 1786, and Reticulum, the agreement between the CMDs of all four clusters indicates that they have the same age. This preliminary analysis suggests that any age differences are smaller than 2 Gyr. These new results mean that there are now 11 old LMC clusters with similar ages. An initial epoch of star cluster formation therefore happened in a short period over a large volume of space, a volume much larger than is now covered by the present-day optical LMC.
The Formation and Evolution of Young Star Clusters in the Antennae
Authors: Whitmore Bradley C.
Published: June 2019

Five populations of young, massive, compact star clusters have been identified in the “Antennae galaxies”, the nearest and youngest example of a prototypical merging galaxy. The brightest of these clusters have all the attributes expected of young globular clusters, hence allowing us to study the formation and evolution of globular clusters in the local universe. Comparisons between the different populations and a variety of multi-wavelength observations are providing new insights into the formation of the clusters. For example, the very red clusters originally identified by Whitmore and Schweizer (1995) appear to be the youngest population, just emerging from their dust cocoon. The cluster luminosity functions for a wide variety of galaxies (i.e., mergers, starbursts, barred galaxies, spirals) appear to follow a “universal” power law, with index ≈ −2. The primary difference between the different galaxies is the normalization, with roughly a tenfold increase in the number of clusters in merging and starbursting galaxies. Hence, the fact that the brightest clusters are in mergers may be largely a statistical result. Simulations are now showing how the initial power law distribution for the clusters will evolve toward the peaked distribution found for old globular clusters, via a combination of processes including two-body evaporation, disk shocking, and stellar mass loss.
Superbubble Metallicities and X-ray Luminosities
Authors: Silich Sergiy , Oey Sally
Published: June 2019

We show that X-ray emission and dynamical properties of superbubbles around OB associations are affected by metal ejection from the enclosed Type II supernovae (SNe). The SN and massive star yields may significantly change the superbubble interior metallicity and enhance its X-ray luminosity.
Formation of Globular Clusters in Turbulent Molecular Clouds
Authors: P. Geyer Michael , Burkert Andreas
Published: June 2019

The formation of massive stellar clusters in turbulent molecular clouds is investigated. We include artificial star formation and energy feedback of newly born stars. The obtained systems are not likely to survive. Case studies to determine conditions necessary for forming bound clusters will be done in the future.
Single and Double Star Astrometry with the Mark III Interferometer
Authors: Hummel C.A.
Published: June 2019

Present construction of large multi-element optical interferometers is based on experience with several pioneering instruments, a very successful one being the Mark III interferometer on Mt. Wilson, California. With it, over the last few years, some 26 spectroscopic binaries were resolved at separations as small as 3 milliarcseconds (mas) and orbital elements have been derived. In addition, the installation of vacuum delay-lines and multi-color fringe-detection allowed the derivation of dispersion-corrected geometrical delays of stars, which were used to determine relative stellar positions over wide angles with a precision of about 20 mas. We present and discuss recent results with respect to the determination of stellar positions, distances, masses, and luminosities.
Hubble Space Telescope: A Generator of Sub-Milliarcsecond Precision Parallaxes
Authors: Benedict G. , Jefferys W. , McArthur B. , Nelan E. , Whipple A. , Wang Q. , Story D. , Hemenway P. , Shelus P. , Van Altena W. , Franz O. , Duncombe R. , Fredrick L.
Published: June 2019

Hubble Space Telescope Fine Guidance Sensor 3 can generate sub-milliarcsecond precision parallaxes in eighteen months. We discuss the internal precision and external accuracy of our observations of Proxima Centauri and Barnard's Star. For some classes of targets Hubble Space Telescope will remain the parallax tool of choice for years to come. It can offer 0.5 mas precision. It will remain useful by satisfying urgent needs for quick results, by offering a 13 magnitude dynamic range, and by providing an unparalleled binary dissection capability.
VLBI Astrometry of Radio-Emitting Stars
Authors: Lestrade J.-F. , Jones D.L. , Preston R.A. , Phillips R.B. , Kovalevsky J. , Froeschle M. , Mignard F.
Published: June 2019

High-accuracy astrometric VLBI observations of 7 radio stars are presented with applications to the connection between the Hipparcos and VLBI extragalactic reference frames, to the identification of the radio emitting region in the ternary system Algol and the detectabity of Jupiter-size planet orbiting the radio star σ2 CrB.
CCD Astrometry of Near—Earth Asteroids
Authors: Monet A.K.B.
Published: June 2019

Automated observations of near-Earth asteroids have been underway at the USNO Flagstaff Station since February 1994. Observations are made with an 8-inch transit telescope utilizing a CRAF/Cassini 1024×1024 CCD. The scale of 1.2 arcsec/pixel provides a field 20.5 arcmin on a side. Pointing and imaging are done automatically using nightly schedules of transit times and declinations of the asteroids to be observed. Observations are made in scan mode, allowing an integration time of 80 seconds at the celestial equator and a limiting magnitude of about 17.5. Flats, collimation and scale frames, and photometric standard fields can all be included in the nightly schedules. The telescope operates unattended during the night, but is monitored remotely by observers at another USNO telescope.
Generation of Sound from Primordial Cosmic Turbulence
Authors: Nariai Hidekazu
Published: June 2019

From the standpoint of the turbulent origin of the formation of galaxies, it is important whether the primordial cosmic turbulence can survive up to the necessary epoch against acoustic decay. This is a preliminary report of our new formalism for attacking the problem.
Mechanisms for the Emission and Absorbtion of Gravitational Radiation
Authors: Misner Charles W.
Published: June 2019

Following some introductory comments on the fundamentals or first principles governing jointly the emission and absorption of gravitational waves, a list is given of observational targets or goals for gravitational wave astronomy which have been selected from recent critical reviews. Then theoretical studies of plunge radiation and gravitational synchrotron radiation are surveyed, since in this area new techniques are developing rapidly although new observational prospects have not yet been found.
The Method of Virtual Quanta and Gravitational Radiation
Authors: Matzner Richard A. , Nutku Yavuz
Published: June 2019

We extend the Weizsäcker-Williams method to the domain of gravitational encounters and correlate collision problems with the corresponding interaction of gravitational radiation. To an ultra-relativistic test particle the field of a Schwarzschild mass appears as a pulse of gravitational plane waves. We consider the scattering of each Fourier component, virtual quanta, by the Newtonian-type field of the test body. The scattered flux at infinity gives us the radiative loss of gravitational energy by a rapidly moving particle.
Perturbations of a Rotating Black Hole
Authors: Teukolsky Saul A.
Published: June 2019

Decoupled, separable wave equations describing neutrino, electromagnetic and gravitational perturbations have been derived (Teukolsky, 1972, 1973). A number of applications have been made (Press and Teukolsky, 1973; Starobinsky and Churilov, 1973).
The Geodetic Interval in a Riemannian Space-Time in the Second Post-Minkowskian Approximation
Authors: John Reiner Wilhelm
Published: June 2019

The knowledge of the geodetic interval between two points in a Riemannian space-time with the metric gab is essential for statements on the time delay in a gravitational field represented by gab and makes possible to derive explicit criteria for clear-cut wave propagation. The nonlinear differential equation for the geodetic interval is integrated via perturbation expansion in the second post-Minkowskian approximation.
Measurements of the 3.3 μm Diffuse Galactic Emission Feature with AROME
Authors: Giard M. , Pajot F. , Lamarre J. M. , Serra G.
Published: June 2019

AROME∗ is a balloon-borne experiment which was built to carry out measurements of IR emission features in the diffuse galactic flux. The field of view is 0.5° and surface brightness gradients are detected through azimuthal scanning at a constant elevation angle. The detection of a feature is done by comparison of the fluxes measured in narrow and wide photometric bands centered on the feature's wavelength. Two flights have been performed (August 1987, October 1988), which detected a 3.3 μm feature in the direction of the galactic plane −6° < b < 6°, 60° > l > −50°. Since this feature is characteristic of aromatic C-H bonds, we assigned it to the emission of transiently heated polycyclic aromatic hydrocarbon molecules (PAHs). With this assumption, AROME measurements show that PAHs are an ubiquitous component of the interstellar matter which contain about 10% of the available cosmic carbon.
Observations of the Extragalactic Background Light
Authors: Mattila K.
Published: June 2019

We present a review of the presently available observations of the extragalactic background light (EBL) obtained by means of night sky photometry. The EBL is a quantity of great cosmological importance; areas which are directly affected include galaxy formation and evolution, the appropriateness of different cosmological models, and the local luminosity density due to galaxies and other matter in intergalactic space. The basic problem in measuring the EBL is its separation from other, much stronger components of the light of the night sky. None of the different observational techniques have succeeded in providing a generally accepted measurement of the EBL. After a review of available methods, we present new results from an experiment by Mattila and Schnur (1989) utilizing the dark cloud technique in the area of L1642, a high-latitude dark nebula in the galactic anticentre direction.
Globular Clusters in NGC 1399 and Background Galaxies
Authors: Madejsky Rainer , Bender Ralf
Published: June 2019

NGC 1399, the central galaxy of the Fornax cluster, is known to have an overabundance of globular clusters (Hanes and Harris, 1986). In order to determine the luminosity function of these globular clusters, two fields near NGC 1399 were observed in the B, V, and R band. One field was chosen near the center of NGC 1399 and the second field 20′ east of the galaxy center. The second field is supposed to contain no globular clusters and is used for comparison. Both fields were reduced with DAOPHOT (Stetson, 1987) to determine the number-magnitude relation for all detected objects (see Figure 1). The differential number counts give log N (m) = 0.84 mB for the comparison field while the differential number counts for the central field (background galaxies and globular clusters) cannot be described by this simple law. Figure 2 shows the number-magnitude relation of the excess objects in the central field (difference between all counts in the central and in the comparison field). The differential number counts N (m) of the excess objects can be represented by the superposition of three populations, each following approximately a Gaussian distribution. The population with the brightest peak luminosity (mB = 22.1 mag) is due to a galaxy cluster with an estimated redshift z = 0.3–0.4.
Figure 1.

The differential number counts of the central field (upper line) and the comparison field (lower line) are displayed for the band until 0.5 mag short of the limiting magnitude. The differential number counts of the comparison field can be described by a simple exponential law; this function is displayed as a dotted line. The differential number counts of the central field cannot be approximated by a simple exponential function.

Figure 2.

The difference among all detected objects between both fields (Ncent(m) - Ncomp(m)) is shown for the B band. The excess objects in the central field can be represented by the superposition of three populations. This three-component Gaussian model is indicated by the dotted line. The most abundant population (N > 250) with peak luminosity mB = 24.8 mag is identified with globular clusters belonging to NGC 1399.
The Infrared Background Due to Galaxies
Authors: Désert F.-X. , Puget J. -L
Published: June 2019

We have investigated the galactic infrared background (GIRB) light that comes from the integrated emission of individual galaxies at different redshifts. By using (1) the galaxy M 82 infrared (IR) spectrum as a template spectrum of IR active galaxies and (2) the constraint given by the nucleosynthesis of the heavy elements in galaxies, we have derived the IR spectrum of the diffuse light that comes from the galaxies at different redshifts following the method by Stecker, Puget, and Fazio (1977). The observations by Matsumoto et al. (1988) impose severe constraints on the possible scenarios for the birth and evolution of the galaxies. Observations by the COBE satellite are expected to settle some important issues of this problem.
A Precise CN Measurement of the Microwave Background at 1.32 mm
Authors: Meyer David M. , Roth Katherine C. , Hawkins Isabel
Published: June 2019

We present very high signal-to-noise observations of the (1,0) and (0,0) vibrational bands of interstellar CN near 3580 and 3874 Å toward HD 21483. Corrected for saturation with a derived b-value of 1.29±0.05 km s-1, these CN line strengths yield excitation temperatures of 2.83±0.09 and 2.76±0.07 K for the J=1-2 and J=0-1 rotational transitions at 1.32 and 2.64 mm. In the absence of local CN excitation, these values represent the brightness temperature of the cosmic microwave background (CMB) radiation at these wavelengths. Millimeter observations have revealed no CN emission at 2.64 mm toward HD 21483 and allow us to set a 2σ upper limit of 0.11 K on the contribution of local processes to the J=0-1 excitation. Considering this limit and the lesser likelihood of local J=1-2 excitation, our observations indicate a CMB temperature of 2.83±0.09 K at 1.32 mm.
X-Ray Background Fluctuations from Discrete Sources with a Varying Density Contrast
Authors: Bi Honguang , Mészáros P. , Mészáros A.
Published: June 2019

In two previous publications (Mészáros and Mészáros 1988 “Paper I”; Bagoly, Mészáros, and Mészáros 1988 “Paper II”), we have studied the fluctuations of the X-ray background (XRB) expected if the XRB is produced by discrete sources distributed as galaxies. The distribution of matter was assumed to follow the large-scale structure in the form of spherical clusters (superclusters) or spherical voids. In Paper I the density contrast of XRB sources inside and outside structures was taken to be a step function of constant height, whereas in Paper II we introduced arbitrary density contrasts (independent of redshift) and allowed for a redshift evolution of the luminosity of the sources. This led to predicted angular fluctuations of the XRB, which, when we compared them with the HEAO–1 observational limit (Shafer 1983), allowed us to set limits on the type and density of structures.
OFFEQ S: Wide–Field UV Imaging with the Israeli Scientific Satellite
Authors: Brosch N.
Published: June 2019

The Israeli Space Agency approved funds for a Phase A study of a scientific satellite to be orbited by a national launcher. Our proposal of an imager in the UV with a 2° field of view (FOV) is one of the two approved for Phase A. We discuss properties of the orbital platform and requirements for the scientific payload. Some scientific programs for the mission are detailed.
Philosophical Behaviourism
Authors: Mundle C. W. K.
Published: June 2019

Professor C. A. Mace, the psychologist, once wrote: ‘It is difficult … to present and defend any sort of behaviourism whatever without committing oneself to nonsense.’ I shall illustrate this thesis. I shall comment on the writings of some psychologists. This is relevant to my topic; for psychologists' expositions of behaviourism contain much more philosophy than science, and the inconsistencies which permeate their versions of behaviourism reappear in the works of eminent philosophers. My quotation from Mace comes from a paper defending what he calls ‘analytical behaviourism’; which he distinguishes from ‘methodological behaviourism’ and ‘metaphysical behaviourism’. According to Mace, analytical behaviourism does not question the truth of our everyday statements about a person's mind or states of consciousness; what it claims is that such statements ‘turn out to be, on analysis, statements about the behaviour of material things’, that is, about a person's ‘bodily acts, bodily states, bodily dispositions, bodily “states of readiness” to act in various ways’. The father of behaviourism, J. B. Watson, rarely says anything suggestingthisdoctrine. As he presents it, behaviourism is both a methodological principle and a metaphysical theory.
Duhem, Quine and a New Empiricism
Authors: Hesse Mary
Published: June 2019

As in the case of great books in all branches of philosophy, Pierre Duhem's Le Théorie Physique, first published in 1906, can be looked to as the progenitor of many different and even conflicting currents in subsequent philosophy of science. On a superficial reading, it seems to be an expression of what later came to be called deductivist and instrumentalist analyses of scientific theory. Duhem's very definition of physical theory, put forward early in the book, is the quintessence of instrumentalism:

A physical theory is not an explanation. It is a system of mathematical propositions, deduced from a small number of principles, which aim to represent as simply, as completely, and as exactly as possible a set of experimental laws [p. 19].
Dreaming
Authors: Kneale Martha
Published: June 2019

If my argument here is successful, it will follow that this paper should have been included in the first volume of this series, The Human Agent (Royal Institute of Philosophy Lectures, 1966–7); for I want to contend that the topic of dreams belongs to philosophy of mind rather than to theory of knowledge.
Comparisons
Authors: Jennings Jesse D.
Published: June 2019

In order to discover the typological similarities of the Wendover collections to artifacts from other sites, and the cultural and chronological inferences such similarities give rise to, a series of collections will be reviewed for comparable data. It is again pointed out that the archeologist's universal assumption — that typological identity between specimens implies either direct or indirect cultural contact or chronological equivalence — is only an assumption. Although much archeological reconstruction of history is rooted in this concept, there are no fixed points of certainty which guide the reconstruction. How much of the values of a culture cling to an artifact? Will a new artifact style or a new class of artifacts have marked influence on the total configuration of a lifeway when the object or complex of objects is introduced into a new culture? If so, how long does the process take? Or do new artifacts reflect some culture change already achieved?

Further, the form and stylistic detail of stone and textile objects, for example, appear to be very stable and to change slowly. Hence, artifacts other than pottery must be regarded as not particularly sensitive to change (in contrast to pottery); inferences based on similarities between textiles or stone work, for example, are likely less apt to carry sharp cultural and chronological implications than are those based on pottery styles.
Statistical Properties of an Unbiased Sample of F7-K Binaries: Towards The Long-Period Systems
Authors: Eggenberger A. , Halbwachs J.-L. , Udry S. , Mayor M.
Published: June 2019

We have undertaken a new investigation of the statistical properties of main-sequence binaries, which is a revision and extension of the Duquennoy & Mayor survey of solar-type stars. The analysis has been divided into two parts: the spectroscopic binaries with periods shorter than 10 years, and the long-period systems including visual binaries and common proper motion pairs. In this contribution we present preliminary results regarding the intrinsic mass ratio and period distributions of visual binaries. Our results are strongly limited by small-number statistics, but when combined with the ones found for the spectroscopic binaries, the following results are obtained: (i) the excess of equal-mass binaries, if still present, is less important for long-period systems than for the binaries with P < 50 days; (ii) the period distribution is inconsistent with a flat distribution.
Volume-Limited Spectroscopic Binary Statistics
Authors: Fisher J. , Schröder K.-P. , Smith Robert Connon
Published: June 2019

We derive the period (P), primary mass (m1) and mass ratio (q) distributions of the local population of field binaries by studying a volume-limited sample of 371 spectroscopic binaries (SBs) in the solar neighbourhood d ≤ 100 pc and Mv ≤ 4. The sample was collated using the Batten catalogue, data of R.F. Griffin and the Hipparcos catalogue. The SB2s are used to calibrate a Monte-Carlo approach to the q distribution of SB1s, giving a total q distribution confirming a peak at q ≈ 1. Completenesses and parameter-specific biases are also assessed. A substantial number of systems with intermediate to long periods are found which may have significant consequences for the mass-distribution of WDs.
The Formation of Binary and Multiple Stars in Clusters
Authors: Bate Matthew R.
Published: June 2019

We discuss theoretical aspects of binary and multiple star formation, focusing on their formation in stellar clusters. First, we review individual processes that may occur during the formation of binary and multiple stars: fragmentation, accretion, interactions with circumstellar discs, and dynamical interactions. We then discuss the results from a recent large-scale hydrodynamical calculation of cluster formation in which all of these processes occur simultaneously, examining the formation mechanisms and resulting properties of the binary and multiple stars in this cluster.
Optical Light Curves of Supernovae
Authors: Leibundgut Bruno
Published: June 2019

Light curves are the most readily available and most frequently used astrophysical tools for variable phenomena. Supernovae are no exception to this. The information that can be extracted from detailed light and colors curves, together with the detailed study of the spectral evolution, tells us about the progenitor star, the various energy input sources, the explosion environment, material in the line of sight and cosmological effects. Over the past decade we have come to understand the power of detailed light curve studies and how they tie into the exploration of other astrophysical topics.
Effects of Small-Scale Fluctuations of Neutrino Flux in Supernova Explosions
Authors: Madokoro Hideki , Shimizu Tetsuya , Motizuki Yuko
Published: June 2019

We examine effects of small-scale fluctuations with angle in the neutrino radiation in core-collapse supernova explosions. As the mode number of fluctuations increases, the results approach those of spherical explosion. We conclude that global anisotropy of the neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given.
The Supernova/GRB Connection
Authors: Höflich P. , Baade D. , Khokhlov A. , Wang L. , Wheeler J.C.
Published: June 2019

We discuss the possible connection between supernova explosions (SN) and gamma-ray bursters (GRB) from the perspective of our current understanding of SN physics. Core collapse supernovae (SN) are the final stages of stellar evolution in massive stars during which the central region collapses, forms a neutron star (NS) or black hole, and the outer layers are ejected. Recent explosion scenarios assumed that the ejection is due to energy deposition by neutrinos into the envelope but detailed models do not produce powerful explosions. There is new and mounting evidence for an asphericity and, in particular, for axial symmetry in several supernovae which may be hard to reconcile within the spherical picture. The 3-D signatures are a key to understand core collapse supernovae and the GRB/SN connection. In this paper we study the effects and observational consequences of asymmetric explosions.
The Astronomy Village: Investigating the Universe
Authors: Pompea S. M. , Blurton C.
Published: June 2019

The Astronomy Village multimedia program is designed to emphasize the process of science as much as its content (Pompea and Blurton, 1995; Pompea, 1996). It was designed for 14 year-old students, but has been used at slightly younger age levels and for older students, including university students. The investigations are flexible enough to be used at this wide variety of levels.

In this CD-ROM-based multimedia program, student teams can pursue one of ten research investigations. In each investigation they are guided by a mentor, receive e-mail, hear a lecture in the Village auditorium, and make observations using ground or space-based telescopes in a virtual observatory. The students also process data using the NIH Image image processing program. They keep a detailed logbook of their research activities and can run simulations on stellar evolution as well as manipulate 3-D astronomy visualization tools.
Spectral Energy Distribution of Be Stars
Authors: Kaiser Dieter , Hanuschik Reinhard W.
Published: June 2019

During two observation periods in Nov./Dec. 1981 and April/ May 1985, absolute spectral energy distributions of 41 southern and equatorial Be stars were photometrically measured at 10 Å spectral resolution in the wavelength range between 3200 Å and 8500 Å, using the scanning spectrophotometer attached to the 61 cm telescope of the University of Bochum at La Silla/Chile. Spectral fluxes of the program stars have been determined with an error of 0m.03 or less.
High-Energy Phenomena in Be Stars (Review Paper)
Authors: Snow Theodore P.
Published: June 2019

It was discovered in the early years of the Copernicus satellite operations that the stellar winds in early-type stars are often characterized by degrees of ionization inconsistent with the spectral types of the stars. The most notable early example was the discovery of strong OVI lines in the form of P Cygni profiles in stars too cool to have this ion in their photospheres, such as τ SCO (BOV; Rogerson and Lamers 1975). Systematic studies showed that excess ionization is a general property of the winds in OB stars (e.g. Lamers and Snow 1978).
Galactic Distribution, Kinematics, Locations in Clusters and H-R Diagrams, and Duplicity of Be Stars (Review Paper)
Authors: Abt Helmut A.
Published: June 2019

The locations of 143 B0e-B7e III-V stars listed in the Bright Star Catalogue are similar to those of the early-B Gould Belt stars. Therefore the Be stars have roughly the same ages and origins as early B stars. The frequency of runaway Be stars must be less than several percent. The radial velocities of Be stars show primarily the reflex of solar motion and show no evidence for systematically negative velocities attributable to mass-loss effects upon the absorption profiles. The scatter in the residual velocities is such that there is unlikely to be many undetected binaries with orbital amplitudes greater than 10 km s-l. We are unable to state whether or not Be stars tend to occur during the overall contraction stage, but we do observe Be stars in roughly constant frequency in clusters of all ages. About 18% of the field B0-B7 III-V stars are Be stars. Clusters show both lower and higher frequencies that may be real or may be due to different observational techniques. The frequencies and distribution of binary periods for Be stars is the same as for non-emission B stars except for the lack of periods less than 10-1 yr. Statistically the 12 classical Be stars with known orbital elements have mass functions indicating that their secondaries are more massive than neutron stars and their secondary mass distribution is like that of normal B stars. We observe 35 companions for 100 Be primaries, so after correction for undetected companions, it seems likely that most Be stars have companions, mostly with periods of years.
An Example Demonstrating the Potential for Asteroseismology of DB White Dwarf Stars
Authors: Bradley P.A. , Wood M.A.
Published: June 2019

We present the results of a parametric survey of evolutionary models of compositionally stratified white dwarfs with helium surface layers (DB white dwarfs). Because white dwarfs are the most common final end state of stellar evolution, determining their internal structure will offer us many clues about stellar evolution, the physics of matter under extreme conditions, plus the history of star formation and age of the local Galactic disk. As a first step towards determining the internal structure of DB white dwarf stars, we provide a comprehensive set of theoretical g-mode pulsation periods for comparison to observations.

Because DB white dwarfs have a layered structure consisting of a helium layer overlying the carbon/oxygen core, some modes will have the same wavelength as the thickness of the helium layer, allowing a resonance to form. This resonance is called mode trapping (see Brassard et al. 1992 and references therein) and has directly observable consequences, because modes at or near the resonance have eigenfunctions and pulsation periods that are similar to each other. This results in much smaller period spacings between consecutive overtone modes of the same spherical harmonic index than the uniform period spacings seen between non-trapped modes. We demonstrate with an example how one can use the distribution of pulsation periods to determine the total stellar mass, the mass of the helium surface layer, and the extent of the helium/carbon and carbon/oxygen transition zones. With these tools, we have the prospect of being able to determine the structure of the observed DBV white dwarfs, once the requisite observations become available.

We are grateful to C.J. Hansen, S.D. Kawaler, R.E. Nather, and D.E. Winget for their encouragement and many discussions. This research was supported by the National Science Foundation under grants 85-52457 and 90-14655 through the University of Texas and McDonald Observatory.
Long Period Variables in the Magellanic Clouds and the Galaxy
Authors: Hughes S.M.G.
Published: June 2019

New results (∼last two years) on mainly observational properties of Long Period Variables (LPVs) in the Magellanic Clouds and the Galaxy are reviewed. These properties include the effects of metallicity variations on their mass loss rates, the use of AGB LPVs to map the stellar distributions of the Galactic disk and bulge, and using detailed observations of nearby Miras to investigate their structure and to obtain new parallax distances, with implications for the pulsation mode of Miras.
Nonlinear Models of Miras, Including Time-Dependent Convection
Authors: Ostlie Dale A. , N. Cox Arthur
Published: June 2019

Nonlinear calculations of Mira variable stars of Population I are presented. Each model is 1 M⊙, with a luminosity of 5000 L⊙ and an effective temperature near 3000 K. These models incorporate our theory of time-dependent convection, which is based on a convective phase lag formalism and includes spatial averaging of convective eddies from adjacent zonal interfaces. The theory also includes turbulent pressure, energy, and viscosity terms and allows for negative convective luminosities in subadiabatic regions where overshooting occurs.

Results of the present study suggest that based upon the dynamic behavior of the models, fundamental mode pulsations are the preferred mode of oscillation. In particular, we do not obtain the chaotic behavior that has been noted in previous nonlinear studies of the fundamental mode oscillations of Miras.
The Opacity Project
Authors: Seaton M.J.
Published: June 2019

The paper gives a brief summary of the work of the Opacity Project.
On the explanation of the Sandage effect
Authors: Catelan M.
Published: June 2019

There are two problems with the Lee et al. (1990, LDZ; Lee 1990, 1991) scenario for the Sandage effect (Sandage 1990 and references therein) which may still warrant further detailed analyses: 1) on the basis of standard tracks, RR Lyrae stars in OoII, M15-like globular clusters can only be well-evolved objects from the blue ZAHB for unrealistically low helium abundance (Y) values; 2) in comparison with the models by Sweigart (1987, SW87), the evolutionary tracks of Lee & Demarque (1990, employed by LDZ) tend to overestimate the effect of evolution away from the ZAHB for the RR Lyrae stars, despite the similar assumptions involved in the calculations of the two sets of models. (See Catelan 1992a, C92A.)
The HF Precise Radial Velocity Programme at DAO
Authors: Yang S. , Larson A. , Irwin A.W. , Goodenough C. , Walker G.A.H. , Walker A. , Bohlender D.
Published: June 2019

A programme to measure precise radial velocities of late-type stars is being carried out at the 1.22-m telescope of the Dominion Astrophysical Observatory (DAO). Wavelength-calibration fiducials are imposed directly on the stellar spectra by passing the starlight through a controlled hydrogen fluoride (HF) absorption cell placed in front of the coude spectrograph. Presently, the primary targets of the programme are bright G, K, and M giants. Preliminary results confirm the low-amplitude, radial-velocity (RV) variability of the yellow giants discovered at the Canada-Prance-Hawaii telescope using the HF technique. These yellow giants and additional bright candidates are now being continually monitored at DAO. Preliminary results also indicate that the “yellow giant” variability extends to the early-M giants. In addition to the RV variations, the data also yield information on the simultaneous variability of the Ca II λ8662 line, Teff, as well as the R - I index of the stars.
Orbital Solution and Physical Parameters of the Binary Cepheid AW Per
Authors: Vinko J.
Published: June 2019

AW Per is a well-known binary Cepheid. Recently Welch & Evans (1989) determined a spectroscopic orbit. Evans (1989) pointed out that the spectral type of the companion is incompatible with the mass function of the system. We re-determined the orbit of AW Per using both photometric and spectroscopic data. The result of the simultanuous least-squares fit can be seen on Fig.l. The orbital elements are very close to the results of Welch & Evans. After correcting for the companion, the Cepheid's light and velocity curves were analyzed with the surface-brightness method. The details of the analysis will be published in MNRAS (Vinko, 1992). The mass of AW Per was found to be 6 solar masses, which confirms the mass-problem of the secondary. Observations are planned to continue at Konkoly Observatory.