bluuebunny/crossref_metadata_2025 huggingface dataset:
A young association in the Large Magellanic Cloud
Authors: Bok B. J.
Published: July 2016

During the past three years, Priscilla F. Bok, Jane Basinski, and I have concentrated in our work on the Large Magellanic Cloud upon the study of young associations. One colour-magnitude array, that of NGC 1955–68–74, has been published (Bok, Bok, and Basinski 1962), and work on three additional groupings, NGC 1929–34–35–36–37, NGC 1770, and NGC 1814–16–20 is well under way. We shall report here on NGC 1929–37, which is often referred to as “Shapley's Constellation I”. Its position is α = 5h22m0; δ = −68°00′ (1960).
The red globular-like clusters in the Magellanic Clouds
Authors: Gascoigne S. C. B.
Published: July 2016

There are about 50 clusters in the Magellanic Clouds which from their spherical symmetry, integrated colours, and luminosities appear similar to the globular clusters in the Galaxy. The colour-magnitude diagrams of these clusters should give moduli for the Clouds, indications of the age and chemical composition of the clusters themselves, and perhaps some information about the evolutionary tracks of old stars generally. The first investigation of this kind was carried out by Arp on the SMC clusters NGC 361 and 419. This was followed by papers by Eggen and Sandage and by the writer on NGC 1783 in the LMC, and by Tifft (1962) on NGC 121 in the SMC. Of these four clusters only NGC 121 appeared really similar to a galactic globular cluster, the others displaying features not reproduced by any known cluster in the Galaxy. Further work was clearly needed to clarify the problems raised by these results, and a program for the systematic observation of the colour-magnitude diagrams of red clusters in the Clouds was accordingly begun here in September 1961. This contribution is a progress report on this program.
Introductory paper
Authors: Morgan W. W.
Published: July 2016

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.
Spectral classification at 42Å/mm
Authors: Jaschek M. , Jaschek C.
Published: July 2016

The object of this communication is to report on the progress of spectral classification at 42Å/mm. The project has been initiated in collaboration with Dr Landi Dessy, whose main interest lies in the types later than F5. The material has been taken with the grating spectrograph of the Bosque Alegre 60-inch reflector of the Córdoba Observatory; the technical details regarding the plate material are reported in Dessy's communication.
Progress report on an atlas for objective-prism spectra
Authors: Seitter W.
Published: July 2016

A Schmidt telescope equipped with objective prisms is a fast and versatile instrument. Indispensable in stellar statistical work, it is equally well adaptable to investigations of interesting individual objects. Most important among its well-known advantages is the fact that photographs of stellar spectra from the infrared to the ultraviolet—limited only by plate sensitivity and the cut-off through atmospheric bands—may be obtained in a single exposure.
A digitized microphotometer and automatic reduction of spectroscopic data
Authors: Yoss K. M.
Published: July 2016

The Jarrell-Ash precision screw microphotometer (Model 23–500) has been equipped with digitized output. The microphotometer itself has a David W. Mann 20 cm lead-screw, accurate to 1 micron. The digitizer is a product of Wang Laboratories.
General remarks on narrow-band photometry
Authors: Strömgren B.
Published: July 2016

During the last decade, a number of procedures for stellar classification on the basis of indices determined through narrow-band photometry have been developed. It appears that satisfactory two-dimensional classification can be carried out in this way for most regions of the Hertzsprung-Russell diagram, and in some regions a relatively high degree of classification accuracy has been achieved. Certain areas of the Hertzsprung-Russell diagram present difficulties, such as a relatively small area on the main sequence around A1 where the hydrogen lines and the Balmer discontinuity reach their maximum. However, it is already clear that the difficulties can be resolved through the addition of further classification indices. Difficulties connected with the effects of interstellar reddening have been overcome; in fact, some of the classification procedures that have been developed lead to high-accuracy determinations of color excesses.
Energy distributions of representative stars in the wavelength region 5000–10 800Å
Authors: Jones D. H. P.
Published: July 2016

1. The relationship between spectral classification and multi-colour photometry is that between high resolution with low photometric accuracy and low resolution with high photometric accuracy. Observations with a spectrum scanner are one method of bridging the gap. The continuum can be measured in regions comparatively free from lines, especially in the red; moreover the stronger spectral features can be measured quantitatively.
Photo-electric uvby and Hβ photometry of magnetic and other peculiar and metallic-line A stars
Authors: Cameron R. C.
Published: July 2016

The observations discussed in this preliminary report were carried out with the 16-inch reflector of the Kitt Peak National Observatory in 1962–63 on the intermediate-banduvbysystem of Strömgren and the narrow-band Hβsystem of Crawford. The two systems are described by Crawford in this symposium. Either T. Kelsall or B. Faure assisted at the telescope during most of the observations.
Narrow-band photometric classification of eclipsing binaries
Authors: McNamara D. H.
Published: July 2016

Although a great deal of work has been devoted in recent years to the problem of improving our knowledge of the spectroscopic and light elements of the eclipsing stars, little effort has been expended on the problem of two-dimensional spectral classification of the component stars on a uniform system. The only serious attempt in this direction appears to be the MK classification of a number of eclipsing stars by Miss Roman (i). Since the light- and velocity-curves of eclipsing systems provide us with fundamental properties such as radii, masses, and densities it is extremely important to have accurate knowledge of the luminosities and spectral types of these objects. In this paper we describe the results of an observational program designed specifically to improve our knowledge of the luminosities and colors of these important stars. The luminosities and colors are then utilized in a discussion of the mass-luminosity relation and effective-temperature scale of stars brigher than the Sun.
On the absolute magnitudes of late-type giant stars
Authors: Ljunggren B. , Oja T.
Published: July 2016

The classification of late-type stars in the Uppsala system is made from photometric measurements of the criteriagandc, gmeasuring the break at the G-band andcthe cyanogen absorption. On the basis of these criteria the stars are divided into luminosity groups. Earlier only two groups, dwarfs and giants, were used. A few years ago a refinement in luminosity classification was introduced (1), the stars being divided into four luminosity groups designated d, dg, g, and c in the order of increasing luminosity. Specially the groups d and g have been defined so as to make them as homogeneous as possible. The group d corresponds to the MK luminosity group V and g approximately to the luminosity group III.
The Ultraviolet Surface Brightness of Reflection Nebulae and the Albedo of Interstellar Grains
Authors: Lillie Charles F. , Witt Adolf N.
Published: July 2016

Satellite observations of the Merope and Barnard's Loop nebulae in the 1050 to 4250 Å spectral region show that the increase in the albedo of interstellar grains below 2000 Å occurs in individual reflection nebulae as well as in the general interstellar medium. Evidence for differences in the composition and size distribution of grains due to variations in the local radiation field is presented.
Southern Reflection Nebulae
Authors: van den Bergh Sidney , Racine René
Published: July 2016

The Curtis Schmidt telescope at the Cerro Tololo Observatory has been used for a two-color survey of reflection nebulae in the Southern Milky Way. Major concentrations of reflection nebulae are found in Carina and in the zone 250° < lII < 270°. A conspicuous gap in the distribution of reflection nebulae occurs at lII ≃ 275°. A detailed photometric and spectroscopic investigation of the stars imbedded in southern reflection nebulae is now in progress.
Depolarization Effect in Reflection Nebulae
Authors: Vanýsek V. , Šolc M.
Published: July 2016

The depolarization effects in reflection nebulae are caused by the size distribution, multiple scattering and irregularity of the grains. In the following abbreviated version of a study of the depolarization effect it is shown that the multiple scattering in reflection nebulae can lead to considerable decrease of the linear polarization. A sample of results obtained by the Monte Carlo method is tabulated.
Elliptical Polarization by Light Scattering by Submicron Spheroids
Authors: Schmidt Th.
Published: July 2016

Calculations have been carried out of single light scattering by Rayleigh type spheroidal dust particles. It can be shown that elliptical polarized radiation with e = v/p ≈ 0.15 can be produced from unpolarized incident radiation, in the case of dirty quartz particles with a refractive index m = 1.54 ± 0.4i and a geometrical axial ratio c: a ≈ 1:2.
Alignment of Dust Grains by Magnetic Relaxation: A Comparison Between Results Obtained by Two Different Methods
Authors: Cugnon P.
Published: July 2016

This paper is devoted to a comparison between results obtained by Purcell and Spitzer (1971) using a Monte-Carlo method and by the author (1971) using a Fokker-Planck equation. It is shown that there is a good agreement between the results within the dispersion expected from the Monte-Carlo method.
The 4830 MHz Formaldehyde Line Observations of Dark Clouds in IC 1795 (W3)
Authors: Minn Y. K. , Greenberg J. Mayo
Published: July 2016

A survey of H2CO absorption in dark clouds in IC 1795 (W3) shows that the material in the direction of W3 can be distinctly separated into three groups: one, immediately surrounding W3, has a uniform velocity of about −41 km–1 s; the second, associated with the W3 (OH) source has a velocity of about −49 km–1 s; the third, as a velocity of about −20 km–1 s and may be associated with an interarm spur in the foreground.
Cosmic X-Rays and Interstellar Dust
Authors: Hayakawa Satio
Published: July 2016

Observational results of cosmic diffuse X-rays are reviewed with particular emphasis on soft X-rays. The intensity distribution of soft X-rays over the celestial sphere indicates that the diffuse component of soft X-rays consists of an extra-galactic and a galactic component. The absorption of the soft X-rays in the interstellar medium results in heating and ionization of interstellar matter. The ionization rate by X-rays is estimated as about 10–16 s–1 per H atom.

The scattering of X-rays by interstellar dust grains produces a halo of an X-ray source and smears out the pulsation of X-ray emission. The scattering coefficient and the halo size are given for some typical grain models.

The possibility that the dust grains gain relativistic energy is suggested. It is speculated that the relativistic dust grains in metagalactic space may be responsible for cosmic rays of ultrahigh energies and also for the diffuse X-rays by the interactions with cosmic black-body radiation.
Optical and Chemical Studies on Simulated Interstellar Grain Materials
Authors: McCullough J. D. , Floyd G. R. , Prince R. H. , Duley W. W.
Published: July 2016

The possibility that many different diffuse interstellar absorption features may be produced by the same type of absorbing atom in different hydrocarbon matrices on interstellar grains has been examined experimentally. The present study shows that absorption bands due to Na atoms in various hydrocarbon matrices can occur within the wavelength range 5400–5800 Å. A study of the molecules generated from the radiation-induced polymerization of C2H2 at 55 K is also reported. It is shown that C6H6 is an abundant product of this polymerization and may therefore be an important constituent of interstellar grains.
Abundances of Interstellar Molecules and Their Formation on Grain Surfaces
Authors: Salpeter E. E. , Watson W. D.
Published: July 2016

Surface phenomena on interstellar dust grains, which are relevant for molecule formation, are summarized. For various molecular species in the interstellar gas, the dependence of abundance on gas density and the degree of shielding of starlight is predicted. These predictions seem to fit with recent observations on carbon-monoxide, but there seems to be a discrepancy for formaldehyde.
The Distribution of Interstellar Molecules in Dust Clouds as Derived from Laboratory Experiments
Authors: Breuer H. D.
Published: July 2016

Irradiation of adsorbed simple gases leads to the formation of rather complex molecules. On the basis of the wavelength dependence and the cross sections for formation and desorption an average molecule density can be estimated. The wavelength dependence further shows that molecules can be formed in denser regions where they are protected from dissociating radiation. A simple model is proposed which shows the molecule distribution as a function of dust density.
New Infrared Sources Associated with H II Regions
Authors: Wynn-Williams C. G. , Becklin E. E. , Neugebauer G.
Published: July 2016

Photometry and mapping in the wavelength range 1.65–20 μ of the H II regions W3 and NGC 7538 have led to the discovery of a dozen new infrared emission sources. The sources have flux densities ranging up to 10–23 Wm–2 Hz–1 at 20 μ and diameters from < 3 to 40″. Some are associated with, and have similar brightness distributions to compact H II condensations observed at radio wavelengths; they have, however, 20-μ flux densities much greater than, and 2-μ flux densities much less than are predicted from the radio free-free spectra. It is concluded that in many cases there exist close spatial relationships between the hot dust and the ionized gas, and between infrared and OH/H2O emission sources.
Hydrodynamic Evolution of Coalescing Compact Binaries
Authors: Rasio Frederic A. , Shapiro Stuart L.
Published: July 2016

In addition to their possible relevance to gamma-ray bursts, coalescing binary neutron stars have long been recognized as important sources of gravitational radiation that should become detectable with the new generation of laser interferometers such as LIGO. Hydrodynamics plays an essential role near the end of the coalescence when the two stars finally merge into a single object. The shape of the corresponding burst of gravitational waves provides a direct probe into the interior structure of a neutron star and the nuclear equation of state. The interpretation of the gravitational waveform data will require detailed theoretical models of the complicated three-dimensional hydrodynamic processes involved. Here we review the results of our recent work on this problem, using both approximate quasi-analytic methods and large-scale numerical hydrodynamics calculations on supercomputers. We also discuss briefly the coalescence of white-dwarf binaries, which are also associated with a variety of interesting astrophysical phenomena.
Mechanisms for Dwarf Nova Outbursts and Soft X-ray Transients: A Critical Review
Authors: Lasota J.P.
Published: July 2016

I review models that try to explain dwarf nova outbursts and soft X-ray transients. The disc instability model for dwarf novae is still in a preliminary state of development: its predictions depend very strongly on the unknown viscosity mechanism. It is also doubtful that a pure disc instability phenomenon will be able to describe all types of dwarf nova outbursts, in particular superoutbursts. The disc instability model for SXTs suffers from the same difficulties but in addition its predictions are contradicted by observations of transient sources in quiescence. The mass transfer model, incorporating illumination of the secondary, cannot describe correctly the time scales of SXT events for main-sequence secondaries with masses less than 1 M⊙. The existence of at least three systems with Porb < 10 hr seems to rule it out as an explanation of the SXT phenomenon.
The Reaction of Low-Mass Stars to Anisotropic Irradiation and its Implications for the Secular Evolution of Cataclysmic Binaries
Authors: Ritter H. , Zhang Z. , Kolb U.
Published: July 2016

A semi-analytic model for the reaction of a low-mass star to anisotropic irradiation of low incident flux is presented. By applying this model to the donor star of cataclysmic binaries (CBs) it is shown that CBs are likely to be unstable against irradiation-driven runaway mass transfer. The implications of this instability for the long-term evolution of CBs are examined. The possibility is discussed that because of this instability CBs evolve through a limit cycle in which phases of high and low mass transfer rate alternate on a time scale short compared to the evolutionary time scale.
The Origin of Type Ib-Ic-IIb-IIL Supernovae and Binary Star Evolution
Authors: Nomoto K. , Iwamoto K. , Suzuki T. , Pols O.R. , Yamaoka H. , Hashimoto M. , Höflich P. , Van Den Heuvel E.P.J.
Published: July 2016

Supernovae are classified as type I and type II and further subdivided into Ia, Ib, Ic, II-P, II-L, and IIb. The origin of this observational diversity has not been well understood. The recent nearby supernovae SN 1993J and SN 1994I have provided particularly useful material to clarify the supernova — progenitor connection. For a progenitor of type IIb supernova 1993J, we propose that merging of two stars in a close binary is responsible for the formation of a thin H-rich envelope. As a progenitor of type Ic supernova 1994I, we propose a bare C+O star that has lost both its H and He envelope after a common-envelope phase. By generalizing these scenarios, we show that common-envelope evolution in massive close binary stars leads to various degrees of stripping off of the envelope of a massive star. This naturally leads to an explanation of the origin of type II-L, IIn, IIb, Ib, and Ic in a unified manner. The binary hypothesis to explain the diversity of supernovae can be substantiated with new information on SN IIb 1993J and SN Ic 1994I. Model light curves are compared with observations. Since extensive mass loss is essential for the binary scenario, circumstellar interactions are examined for comparison with X-ray observations.
Planets Around Pulsars
Authors: Wolszczan A.
Published: July 2016

A discovery of three terrestrial-mass planets orbiting the millisecond pulsar PSR B1257+12 and a subsequent detection of the predicted effect of gravitational interaction between the two more massive planets confirms that the first extrasolar planetary system has been identified and that pulsars can be successfully used as probes of planetary dynamics. In the absence of detections of planet-sized objects around Sun-like stars, planets orbiting a precise pulsar clock represent a unique source of information concerning the origin and evolution of planetary systems.
Supersoft ROSAT Sources in the Galaxies
Authors: Kahabka P. , Trümper J.
Published: July 2016

Before the X-ray surveys performed with EINSTEIN and ROSAT soft X-ray (or EUV) sources were claimed to exist (Iben 1982; Fujimoto 1982); they were looked for in the ultraviolet and indeed such sources were found in the symbiotic systems (which count as CV-like systems) and termed the hot component of symbiotics. Although the nature of these hot components has been subject to debate (in terms of either nuclear burning white dwarfs or accretion phenomena) observational facts were in many systems favouring the first scenario (Mikolajewska & Kenyon 1992). Symbiotic binaries require wide orbits in order to keep the big giant star within its Roche lobe. It is natural to look for the short-period counterpart, but it was much more difficult to detect them in the optical due to the faintness of the secondary, which is supposed to be an evolved main-sequence star or even smaller. What turns out in these systems to be predominant is the much brighter accretion disk. It was the unique chance of the satellite borne X-ray imaging instruments to discover these EUV and soft X-ray sources and with the EINSTEIN observatory the first firm candidates were found. However, complete coverage of the soft X-ray sky was needed in order to get them all and ROSAT was the instrument which mapped the whole sky.
The state of the art in helioseismic ground-based experiments
Authors: Pallé Pere L.
Published: July 2016

The new results obtained from the observation of solar oscillations over the past decade, have a direct impact on our knowledge of the Sun's interior. As a consequence, a great interest in helioseismology has arisen and is reflected in the development of new observational projects as well as new analyse and inversion techniques. In this review we will describe the present ground-based observational programmes, which, unlike the space ones, are mostly designed to produce high quality data over very long time spans (up to solar cycle time scales). The characteristics of the various observational programmes, single-site and network, will be described together with their performances, the main results obtained up to now, and some other logistical aspects.
Giant planets seismology
Authors: Mosser B.
Published: July 2016

The giant planets Jupiter and Saturn belong to the interesting category of possible goals for remote seismic analysis. Their first seismic observations and their analysis were attempted in 1987 and 1991 respectively, under Philippe Delache's initiative. The theoretical analysis of giant planets seismology reveals the strong signature of the dense planetary core and the tiny one of the hydrogen plasma phase transition. The asymptotic formalism makes possible to obtain pertinent information for the observation of planetary oscillations and for their analysis. Specific observational techniques were developed to detect the seismic signature of giant planets. However, the first observations (Schmider et al. 1991, Mosser et al. 1993) of Jovian oscillations remain tentative. Even if the Jovian origin of the signal is beyond doubt, the interpretation in terms of Jovian global modes remains speculative. The collision of comet SL9 onto Jupiter provided an unexpected and unique opportunity to search for oscillations excited by the cometary impacts (Mosser et al. 1996). Seismic observations of Saturn remain negative so far. Therefore, this review focuses on Jupiter. Finally, the almost 10-years long experience of seismic observations of Jupiter and Saturn has not yet provided new constraints for planetary interior models. However, guidelines for future observational projects dedicated to Jovian seismology can be drawn. The different techniques of observation are compared, and observational requirements are precisely described.
Probing the interiors of roAp stars: stellar tubas that sound like piccolos
Authors: Matthews Jaymie M.
Published: July 2016

Chemically peculiar magnetic (Ap) stars in the Instability Strip shouldn't really pulsate (since the helium in their very stable atmospheres appears to have gravitationally settled below the He II ionisation zone). And if they did pulsate, they should have periods of a few hours like the δ Scuti variables, since the Ap stars have comparable mean densities and their atmospheric peculiarities wouldn't strongly affect the global eigenfunctions of low-degree p-modes.
HST Observations of the L1551 IRS5 Jet
Authors: Fridlund Malcolm , Huldtgren Monica , Liseau Rene
Published: July 2016

The jet emanating from the young stellar object, known as IRS5, located in the molecular cloud L1551 in Taurus has been imaged with the Hubble Space Telescope. The observations and a preliminary interpretation of them is presented. The relevant background history for this important object is briefly reviewed.
Thermal Radio Jets
Authors: Rodriguez Luis F.
Published: July 2016

Since thermal radio jets can be observed with subarsecond angular resolution and are unaffected by dust absorption, they provide a useful tool to study collimated outflows very close to the young stars that produce them. Here, I review recent results on this area, giving emphasis to the study of thermal jets in the case of the quadrupolar outflows in L723 and HH 111.
Molecular Hydrogen Emission in Embedded Flows
Authors: Eislöffel Jochen
Published: July 2016

This overview of recent observations of molecular hydrogen (H2) in outflows from young stars discusses the morphology, the excitation and the kinematics of the H2gas in these flows. A comparison between the H2and CO outflows will lead us to the conclusion that highly-collimated jets may drive the latter. We also discuss the mechanisms which can entrain ambient molecular gas into the jet flow.
Observational Properties of Molecular Outflows
Authors: Padman Rachael , Bence Stephen , Richer John
Published: July 2016

Molecular outflows are intimately related to the highly collimated Herbig–Haro jets emanating from young stars. In consequence, the usual dynamical timescale significantly underestimates the true age of an outflow. If we correct for this factor, and assume an intrinsic outflow speed similar to that of the underlying jet, we predict that molecular outflows should have an overall extent of several parsecs, in accordance with recent results. It seems likely therefore that outflows are a major source of interstellar turbulence, and have a profound impact on the process of star formation.

Whilst interpretation of jet-like outflows is relatively straightforward, the origins of shell-like outflows, such as that from L 1551–IRS5, are less obvious. We discuss the current observational status of both types of flow, and hypothesize an evolutionary connection between them. A large and well-defined outflow sample is urgently required, to permit the establishment of an age-sequence; such a sample would also provide the basis for a proper investigation of outflow energetics and interaction with the ISM.
Models of Bipolar Molecular Outflows
Authors: Cabrit Sylvie , Raga Alex , Gueth Frederic
Published: July 2016

This paper reviews various hydrodynamical models proposed for explaining bipolar molecular outflows from young stars. The different possibilities discussed are : wind-driven molecular shells, steady state filled flows, and jet-driven bow shocks. Particular emphasis is placed on comparisons between model predictions and observations of molecular flows. While it appears that jet-driven bow shocks are at the present time the most popular mechanism for explaining molecular outflows, other models have interesting characteristics that might be relevant for at least some objects.
Energetics, Collimation and Propagation of Galactic Protostellar Outflows
Authors: Camenzind Max
Published: July 2016

Formation of jets in low-mass protostellar objects and young pre-main sequence stars is ultimately related to the existence of some gaseous disk around a rapidly rotating central object. This configuration has deep parallels to extragalactic systems such as radio galaxies and quasars. Rotating black holes are still thought to be the prime-mover behind the activity detected in centers of galaxies, while, in the case of protostellar jets, rapidly rotating stars and disks are responsible for the ejection of bipolar outflows. In both cases, magnetic fields are invoked for the acceleration, the collimation and propagation of these outflows. The ultimate rooting of these fields is still under debate. We discuss models where winds injected into rapidly rotating magnetospheres of the central object drive the outflows. From these considerations it follows that the jets of young stellar objects can only be produced magnetically and that their progagation is determined by their magnetic properties. Such jets have low Mach numbers ≃ 2 and their instabilities are dominated by the pinch mode. Knots closest to the source are attributed to compression by the time-dependent pinches. Multiple bow shocks occur on longer time-scales (a few thousand years) and are attributed to variations in the magnetospheric structure of the star, or the disk.
Numerical Simulations of Optical Knots in YSO Outflows
Authors: Rubini F. , Lorusso S. , Giovanardi C. , Leeuwin F.
Published: July 2016

The aim of this work is to show that, though 3D effects should be invoked to explain the less regular arc-like regions, the internal knotty emissions may be explained through a roughly axisymmetric pattern of oblique shocks.

To this purpose, numerical simulations of non-equilibrium, radiative, hydrodynamical jets in axisymmetric geometry have been performed. After showing that the internal reflecting waves, travelling in the beam of a stellar jet, steepen into oblique shocks, we verify that the optical emission arising from the shocked regions is in good agreement with observations.

Since the optical emission strongly depends on the physical and chemical parameters, (namely temperature and electron densities inside the emitting regions), special care is devoted to solving the energy transport equation.
On the Energetics and Momentum Distribution of Bow Shocks and Colliding Winds
Authors: Wilkin Francis P. , Cantó Jorge , Raga Alex C.
Published: July 2016

We discuss recent progress in analytic modeling of stellar wind bow shocks and colliding winds. For thin, radiative shocked layers in steady-state, the shape of the layer as well as its internal flux of mass and momentum are found from the conservation laws of mass, momentum and angular momentum. For the case that the shocked gas is well-mixed, the velocity distribution and mass column density of shocked material are also obtained. These solutions are extended to the problem of a jet bow shock, treated as a non-isotropic “wind” interacting with the ambient medium. We also examine the shell energetics for these simple analytic models. The constraint of conservation of momentum leads to an upper limit to the efficiency of thermalization and radiation of the pre-shock wind kinetic energy. Calculations are presented of this thermalization rate as a function of the input momentum rates of the pre-shock winds.
Hubble Space Telescope Imaging of the Disks and Jets of Taurus Young Stellar Objects
Authors: Stapelfeldt Karl , Burrows Christopher J. , Krist John E. ,   The WFPC2 Science Team
Published: July 2016

We report on Hubble Space Telescope imaging of eleven young stellar objects in the nearby Taurus molecular clouds. The high spatial resolution and stable point spread function of HST reveal important new details of the circumstellar nebulosity of these objects. Three sources (HH 30, FS Tau B, and DG Tau B) are resolved as compact bipolar nebulae without a directly visible star. In all three cases, jet widths near the sources are found to be 50 AU or less. Flattened disk structures are seen in absorption in HH 30 and FS Tau B, and in reflection about GM Aur. Extended envelope structures traced by scattered light are present in HL Tau, T Tau, DG Tau, and FS Tau. The jet in DG Tau exhibits a large opening angle and is already resolved into a bow-like structure less than 3″ from the star.
Properties of the Winds of T Tauri Stars
Authors: Calvet Nuria
Published: July 2016

The properties of Classical T Tauri (TTS) winds - their mass loss rate, temperature, origin, and energetics - are reviewed and interpreted in terms of the most recent observational evidence. TTS winds seem to have their origin in the disk and are powered by accretion. Most TTS have Ṁω ≤ 10–9Mʘ yr–1 and Ṁω/Ṁ ∼ 0.1, with T ∼ 104K.
The Evolution of Flows and Protostars
Authors: André Philippe
Published: July 2016

In this paper, I summarize the key properties of Class 0 protostars, discuss the observational evidence for a decline of outflow/inflow power with evolutionary stage, point out a possible connection with the initial conditions of fast protostellar collapse, and suggest a new collapse scenario in regions of induced, multiple star formation. The main thesis put forward here is that Class 0 objects have unusually powerful outflows because they accrete at a substantially higher rate than their Class I descendants.
Millimeter Interferometry of Class 0 Sources: Rotation and Infall Towards L1448N
Authors: Terebey Susan , Padgett Deborah L.
Published: July 2016

In order to study the kinematics of protostellar collapse we present high-spatial resolution millimeter interferometer data of the class 0 source L1448 N. The L1448 N cloud core has fragmented into two rapidly rotating subcores containing three protostars. One subcore is a protobinary system with 2000 AU separation. Strong evidence for infall is seen towards the N(B) component.
Massive Star Formation: Observational Constraints
Authors: Churchwell Ed
Published: July 2016

Observations during the past several years strongly imply that virtually every star, independent of final mass, goes through a phase of rapid outflow simultaneously with rapid accretion during formation. The structure and properties of outflows and accretion disks associated with low-mass star formation has received intensive observational attention during the past several years (see the reviews and references in Lada 1985; Edwards, Ray, and Mundt 1993; Fukuiet al.1993; and this symposium). Young stellar objects (YSOs) with Lbol< 103L⊘will be referred to as “low-mass” stars in this review. The range of physical properties of CO outflows associated with YSOs of all masses are enormous, see Fukuiet al.(1993). I will focus attention in this review on what we know about massive YSOs and their environments.
Low-Mass Versus High-Mass Star Formation
Authors: Hartquist T. W. , Dyson J. E.
Published: July 2016

Structures like the clumps identified in the CO maps of the Rosette Molecular Cloud and the dense cores such as those in B5, a cluster of cores and young low-mass stars, are key to considerations of star formation. Whether star formation is a self-inducing process or one that causes itself to turn off depends greatly on whether the responses of the interclump and intercore media to young stars cause the collapse of clumps or cores to be faster than their ablation. We present a naive introduction to the lengthscales over which such responses are significant, mention ways in which the responses might induce collapse, review some of the little that is known of how flows of media around clumps and cores ablate them, and then return to the issue of the lengthscales over which such responses are significant by considering the global properties of mass-loaded flows in clumpy star forming regions.
Conference Summary
Authors: Raga A. C.
Published: July 2016

The present paper reviews the talks and poster papers presented at the IAU 182 symposium. The papers are divided into different subjects, highlighting their contributions to the field of outflows from young stars. The observational contributions were notable because of the results recently obtained with new instruments (e. g., with radio interferometers and space based observatories). The theoretical contributions were noted by the increased understanding of the production of collimated winds from young stars, and by numerical and analytic work on the propagation of the outflows.
Rotation in Close Binaries
Authors: Rajamohan R. , Venkatakrishnan P.
Published: July 2016

It has been demonstrated (Zahn 1966 a, b, c; 1975, 1977) that turbulent viscous dissipation of tides can brake the rotation of stars having convective envelopes, while radiative dissipation can do like-wise for those having radiative envelopes. The time scales for the former are very small whereas those for the latter depend sensitively on the ratio r/R where r is the radius of the star and R, the binary separation. For most systems these turn out to be much less than their main sequence lifetimes. This fact affords a natural explanation for the preponderance of synchronous systems.
A New Method of Light Curve Analysis: Application to V444 Cygni
Authors: Smith S.A.H. , Theokas A. C.
Published: July 2016

A new method of light curve analysis is introduced for systems involving an atmospheric eclipse. Occultation or partial eclipses may be treated, with or without the presence of transparency effects. Besides admitting an arbitrary degree of transparency to the eclipsing component, an arbitrary law of limb darkening may also be given the eclipsed star.

The method has successfully been applied to the study of narrow band continuum light curves of V444 Cygni obtained by Cherepashchuk and Khaliullin. Primary and secondary minima are examined separately.
Evolution of Intermediate Mass Close Binaries
Authors: Van Der Linden Th.J.
Published: July 2016

Numerical simulations of close binary evolution were performed for five binary systems, using a newly developed evolutionary program. The systems have masses 3+2, 4+3.2, 6+4, 9+6, 12+8 M⊙ and periods 2d, 1d78, 3d, 4d, 5d respectively. The primary component was followed from the zero-age main sequence through the mass transfer phase to core-helium burning. Special care was given to the self-consistent determination of the mass transfer rate and the detailed treatment of composition changes. After the mass transfer phase the resulting systems consist of a main sequence star with a helium star companion of mass 0.36, 0.46, 0.82, 1.48, 2.30 M⊙ for the five systems respectively. Interesting “thermal pulses” were found in the 3+2 M⊙ system at the onset of helium burning.
The Be Star Φ Persei
Authors: Poeckert R.
Published: July 2016

He II (λ 4686) emission has been detected in the spectrum of the binary Be star ɸ Persei. The He II emission has velocity variations which are 180° out of phase with the velocity variations of the primary. The primary velocity curve is determined from the broad He I and H lines, and the Fe II emission lines. The amplitude of the primary velocity curve (K1) is 16 ± 2 km s−1. The amplitude of the He II velocity curve is 121 ± 9 km s−1.

If one assumes that the He II emission arises from the secondary, minimum masses for the primary and secondary are 29 ± 14 M⊙ and 3.8 ± 1.7 M⊙, respectively. We suggest that the secondary is a hot compact star, either the remaining helium core of a once more massive star, or a neutron star. The primary is too cool, Bl IIIe, to have any appreciable He II emission.
Hα Emission Line Profiles in the Spectrum of Algol
Authors: Bolton C. T. , Zubrod Donna J.
Published: July 2016

We have investigated variations in the strength and profile of the Hα emission line in the spectrum of Algol using 145 16 A° mm−1 spectrograms obtained during the period September, 1976 to December, 1977. The Hα emission line profile has been extracted by subtracting the absorption contributions of the three stars in the system. The resulting data set has been analyzed to look for variations related to orbital phase as well as shorter and longer term variations.
Structure of the Gaseous Disk in RX Cas
Authors: Kříž S.
Published: July 2016

RX Cas appers to be a long-period Algol-like binary with very fast mass exchange (Struve 1944). In the period 1975-1977, this star was observed photometrically by Arsenijevič, Grygar, Harmanec, Horn, Koubský, Kříž and Pavlovski at Hvar Observatory (Yugoslavia) and by Zverko at Skalnaté Pleso Observatory (Czechoslovakia). The resulting UBV light curves seem to be rather peculiar, for the following reasons:

1) Combining our observations with the older ones, we obtain the following formula for the times of minima:

The period increase is surprisingly high.

2) The scatter of observed points is considerable (about 0.2 mag.) and cannot be caused by observational errors. It corresponds to short period light variations on the time scale of several days.

3) After J.D. 24422660, the brightness of the whole system decreased in all colours. This decrease is about 0.2 mag. in V colour and 0.5 mag. in U colour. Only after J.D. 2442900 the brightness increased again. Such a behaviour confirms the reality of old observations by Gaposchkin (1944) and Martynov (1950) who found a long-term light variation with a period of approximately 500 days.

4) The part of the light curve around the phase 0.75 is definitely much lower than the corresponding part around the phase 0.25. This effect is most pronounced in the ultraviolet; the depression around the phase 0.75 is much deeper than the secondary minimum. This behaviour is opposite to the behaviour of dwarf novae. Instead of a bright shoulder connected with a bright spot, we observe some darkening.
Re-Evaluation of the Orbital Elements of HDE 226868 = Cyg X-1
Authors: Bolton C. T. , Gies Douglas R.
Published: July 2016

We have scanned 75 high dispersion spectrograms of HDE 226868 = Cyg X-1 with the PDS microdensitometer of the David Dunlap Observatory in preparation for a detailed spectrophotometric study of the system. The plate material is identical to that described by Bolton (1972a,b,1975) and includes those plates. We have determined velocities for all of the spectrograms by fitting a parabola to the bottom of each line profile. The lines were divided into three groups, hydrogen lines, He I lines, and high excitation lines (He II, Si III and IV, N III), according to excitation, and separate mean velocities were determined for each group on each plate. We have computed the orbital elements of the system separately for each line group in order to look for differences caused by the effects of mass transfer or stellar wind.
SS 433 as a Magnetic X-Ray Binary
Authors: Collins G.W. , Newsom G. H. , Boyd R. N.
Published: July 2016

In this paper we expand upon a proposed model for SS 433. Specific attention is given to the manner in which the light travel time within the system places constraints upon the geometrical parameters defining the system. Consideration is also given to the physical situation which exists in the high Doppler shift emitting region. Implications of recent observations of “a 13-day” period spectral and light variability upon the central source are briefly discussed.
Out-of-Eclipse Light Variation of RS CVn Stars
Authors: Catalano S. , Frisina A. , Rodonò M.
Published: July 2016

The photoelectric observations of the close binary RS CVn carried out at Catania Observatory from 1963 to 1973 are presented. A new period of 9.48 years for the retrograde migration of the wave-like distortion on the light-curve has been determined. The wave amplitude is found to undergo cyclic changes with a period of about 4.74 years.

Possible correlation between the wave amplitude and the inclination of the rotational axis and the spectral type of the spotted component for several RS CVn and BY Dra binaries is investigated.
The Nature of the Difference Between Novae, Dwarf Novae, and Novalikes
Authors: Mitrofanov I. G.
Published: July 2016

Novae (N) and Dwarf Novae (DN) are considered to belong to the class of the Cataclysmic Variables (CVs). The Novalike stars and recently discovered Polars (the AM Herculis-type stars) seem to have the same nature as CVs and probably are members of this class. It is usually assumed that CVs are close binary systems, each system contains a degenerate dwarf and a nondegenerate second component, their period being usually less than 16h (e.g. see: Robinson 1976). A second star is believed to overfill its Roche lobe and its matter flows onto the degenerated component. Then around the degenerated dwarf there arises an accretion disk. This disk and the hot spot where the interaction between the disk and outflowing stream occurs are the main sources of the blue and ultraviolet continuum and strong H and He emission lines.
Upper Limits for the Luminosity of a dM Companion in AM Herculis Objects
Authors: Tapia S. , Coyne G. V.
Published: July 2016

The quest for optical identification of X-ray sources has revealed a new class of variables currently formed by AM Her, AN UMa, VV Pup, and the most recent member, 2A 0311-227 (for which a variable star designation will be available soon). These objects show many of the variations common to close binary systems where mass transfer is under way. However, they are distinguished by the high degree (10 to 35 %) of linear and circular polarization observed in the optical and near infrared spectral regions. Apparently the polarization is due to cyclotron emission of electrons located in a region where the magnetic field strength is about 108 gauss.
Rotation Broadening and the Shapes of W Ursae Majoris Stars
Authors: Anderson Lawrence , Raff Malcolm , Shu Frank H.
Published: July 2016

We extract rotation broadening functions from the spectra of W Ursae Majoris Stars. Using a fast Fourier transform we deconvolve photographic spectra, covering some 500 A including dozens of strong lines, with equivalent spectra from non-rotating stars of similar spectral type. The resulting rotation functions contain information about global features such as the shape of the stellar surface (e.g. mass ratio and degree of contact), gravity brightening and limb darkening. We present preliminary data on the stars VW Cep and ER Vul. The rotation function of the former reveals the presence of the third component found visually by Heintz (1975), while that of the latter shows it to be detached and have mass ratio 0.9.
Ultraviolet Observations of 31 and 32 Cygni
Authors: Stencel Robert E. , Kondo Yoji , Bernat Andrew P. , McCluskey George
Published: July 2016

Ultraviolet observations of the Zeta Aurigae systems appear to have several advantages over comparable visual wavelength studies. A wide range of large optical depth resonance lines of abundant species permit the study of the supergiant atmosphere and circumstellar environment at virtually all phases. The International Ultraviolet Explorer satellite (Boggess, et al., 1978) is well suited to obtaining spectra between 1150 and 3200 A, although the competition for observing time is non-negligible.
The Formation of Planetary Nebulae with Close Binary Nuclei
Authors: Saltzman J. , Livio M. , Shaviv G.
Published: July 2016

Recent observations of nuclei of planetary nebula have shown that some of the central stars are binaries and even close binaries with periods of hours to few days.
Atmospheric turbulence effects on astrometric determinations
Authors: Ivanov V. I.
Published: July 2016

It is well known that the turbulent state of the atmosphere gives rise to fluctuations of the coefficient of light refraction. In astrometric observations these fluctuations produce the phenomenon of image motion which serves as the source of accidental errors of observations. The need for the study of the effect of atmospheric turbulence is documented in (G.Teleki, 1967) and others.
Investigation on refraction in trigonometrical leveling traverses
Authors: Blažek Radim
Published: July 2016

When investigating refraction in trigonometrical traverses, additional observations for vertical angles have made it possible to evaluate the coefficient of refraction for each station. The improvement in elevation accuracy was substantial in traverses with longer distances (about 4 km) between stations.