bluuebunny/crossref_metadata_2025 huggingface dataset:
Dust Grains in Reflection Nebulae
Authors: Zellner Ben
Published: July 2016

Observations and Mie theory calculations of colors and polarization in several reflection nebulae are compared.
Interstellar Circular Polarization of Upper Scorpius Stars
Authors: Kemp James C.
Published: July 2016

Circular polarization of interstellar or perhaps circumstellar origin has been clearly established in two reddened stars in the Upper Scorpius region, o-Sco and σ-Sco A; and detected preliminarily in a third, HD 154445. In the Corning 5–60 filter band λλ 3800–4600, measured values of 104q were: o-Sco, –(2.9 ± 0.2); σ-Sco A, –(1.7 ± 0.2); and HD 154445, +(2.8 ± 0.8). Complete wavelength dependences q(λ) for o-Sco and σ-Sco A are under study, but so far are known to have the following similarity. Each shows a broad maximum (of negative q) centered in the range λλ 3800–4300; and the values are smaller by a factor ~ 4, but still negative, in the range λλ 5000–6000. The effect here is most likely due to a twisting grain alignment along the line of sight. In that case a simple model predicts q(λ) ∝ (n′l – n′r) · (n″l – n″r) θ0z02, where n = n′ +i n″ is a formal, complex refractive index (in van de Hulst's forward-scattering approximation), l and r referring to longitudinal and transverse grain axes, and θ0 is the total twist angle over the interaction length z0. An alternate mechanism would be multiple scattering (at large angles, not along the line of sight) within asymmetrical, well-localized clouds around the individual stars. The similar sign and magnitudes of q for o-Sco and σ-Sco A, which are 1.5° apart in the sky, argue for the line-of-sight mechanism – for example through a large cloud in front of the entire local region. Comparative studies of many stars in Upper Scorpius will be of obvious interest.
The Association of Dust and H I Gas
Authors: Braunsfurth E. , Rohlfs K.
Published: July 2016

The hypothesis that interstellar dust is associated with cold gas is advanced. To test this, such observational features of the gas that depend predominantly on the cold gas have to be isolated. Two such features are discussed, the 21-cm line strength in absorption and the intensity of narrow emission line components in intermediate galactic latitudes. It is shown that both features have a good correlation with the dust extinction. Various measurements of the gas to dust ratio are collected and some implications for the interstellar medium are discussed.
Observations of Atomic Hydrogen in Dense Interstellar Dust Clouds
Authors: Knapp Gillian R.
Published: July 2016

High frequency resolution 21-cm line observations of almost 100 interstellar dust clouds showed that about one-third of them contain significant amounts of cold neutral hydrogen. Simple models for the velocity distribution of hydrogen in the clouds were fitted to the observations, and spin temperatures ranging from 16 to 40 K and column densities from 7 × 1019 to 6× 1020 atom cm–2 were found. The ratios of H i to OH and H i to dust in the clouds were found to have about 1 to 10 % of their value in the general interstellar medium.
The Correlation of Interstellar Reddening and Lα Absorption
Authors: Jenkins Edward B. , Savage Blair D.
Published: July 2016

For 61 stars whose interstellar Lα absorption was observed by OAO-2, the average relation of H I column density to B – V color excess is equal to 5 × 1021 atoms cm–2 mag–1. For a recent dust grain model this value implies that the density ratio 〈ρHI/ρdust〉 ≈ 100. A good correlation was found for deviations in the measurements of NHI and E(B – V) from their mean values expected over the distances to the different stars, indicating an association of H I gas with dust.
Optical and Photoemission Properties of Graphite Grains
Authors: Willis R. F. , Feuerbacher B. , Fitton B.
Published: July 2016

The optical properties and collective excitations are discussed for graphite and vitreous carbon. The bulk resonance energy for the π-plasmon is seen to be shifted by 1.4 eV from the crystalline to the amorphous case, indicating that the degree of structural disorder is an important parameter in the optical properties of carbon grains. Data are presented on work function, photoelectric yield, and photoelectron energy distribution for both graphite and vitreous carbon. Under solar irradiation, photoelectrons from graphite are emitted with an average energy of about 1 eV (12000 K).
Photoelectron Emission from Interstellar Grains
Authors: Watson William D.
Published: July 2016

Photoelectric emission from interstellar dust grains due to ultraviolet starlight is reinvestigated. Ejection of photoelectrons can make a substantial contribution to the heating of standard interstellar clouds. Both positive and negative grain charges are shown to be possible.
The Surprising Constancy of Relative Chemical Abundances in Different Regions of Interstellar Space – Particularly for Formaldehyde
Authors: Heiles Carl , Gordon M. A.
Published: July 2016

Many of the places in which radio astronomers search for molecules are located in exotic regions lying near the galactic center, near H II regions or other continuum sources, or in high density regions. Such regions have wide variations in their physical environment. Here we wish to compare two types of region whose environments are thought to be well-understood. One of these is dust clouds; the other is unshielded (from UV) cold clouds in front of bright radio sources. For the sake of interest, we include without comment results for molecular regions near the Galactic center and near Orion A.

Comparison of dust clouds and unshielded clouds is of interest because the volume density differs by a factor of 104 or more and the extinction differs by 8 mag. or more. Neither type of cloud lies near H II regions or other sources of intense radiation. Even though their properties differ widely, we will see that the abundances of OH and H2CO relative to hydrogen are approximately the same in the two. Although this is understandable for OH, no current theory would predict this situation for H2CO.
Physical Study of a Bright Rim in the Horsehead Nebula
Authors: Louise R. , Sapin C.
Published: July 2016

The wellknown ‘Horsehead’ nebula is photographed with narrow interference filters centered respectively on Hα and [N II] (λ = 6584 Å). The [N II]/Hα ratio is deduced and its variation towards the Horsehead bright rim is studied. It is shown that the maximum value of the temperature is not reached on the rim itself but in a narrow zone located just behind it and ahead of the dark matter.
A Statistical Model for the Cloud Structure of the Interstellar Medium
Authors: Taff L. G. , Savedoff M. P.
Published: July 2016

We have formulated and studied the properties of a mathematical model intended to span between the hydrodynamical and discontinuous regimes. Model parameters and predictions permit matching the observed mass spectrum of those interstellar clouds with masses between 103 and 106M⊙. The central element of the theory is the specification of P (m, m′, μ, μ′, … μ″), the conditional probability that once a collision has occurred between clouds of mass m, m′ the result is clouds of mass μ, μ′, … μ″. For stable solutions to exist we require that the total mass in the system be conserved. Such simple models as total coalescence, geometric overlap and partition statistics were considered for P as well as several probabilities based on possible physical conditions that might prevail in cloud-cloud collisions. One immediate numerical result of these models is that nearly total coalescence must obtain in actual cloud-cloud collisions before one can build up a non-infinitesimal concentration of large mass couds. Field and coworkers (1965, 1968) indicate that total coalescence would produce a minimum in the mass spectrum and that as the position of the minimum went to infinity the spectrum itself more closely approximates a power law curve with index − 3/2. In none of our calculations was anything but strict monotonic decrease observed and under the same physical assumptions as Field the curve we obtain (analytically) has no minimum, independent of the largest mass in the system. Both of these spectra are flatter than recent observational evidence indicate. True equilibrium solutions exist in our formulation with an e-folding time ≃ 107 yr for objects such as these. We are continuing work on the detailed time evolution of interstellar clouds in particular and formulating other astronomically interesting applications of the general theory.
A Quick Review of Interstellar Grains
Authors: Van De Hulst H. C.
Published: July 2016

This paper reviews the results of the Symposium on Interstellar Grains. It draws some historical lines and emphasizes the questions that require further study.
The Structure and Evolution of Thorne-Żytkow Objects
Authors: Podsiadlowski Philipp
Published: July 2016

Thorne-Żytkow objects (TŻOs) are red supergiants with neutron cores. The energy source in TŻOs with low-mass envelopes (≲8 M⊙) is accretion onto the neutron core, while for TŻOs with massive envelopes (≲14 M⊙) it is nuclear burning via the exotic rp process. TŻOs are expected to form as a result of unstable mass transfer in high-mass X-ray binaries, the direct collision of a neutron star with a massive companion after a supernova or the collision of a neutron star with a low-mass star in a globular cluster. We estimate a birth rate of massive TŻOs in the Galaxy of ∼2 10−4 yr−1. Thus, for a characteristic TŻO lifetime of 105–106 yr there should be 20–200 TŻOs in the Galaxy at present. These can be distinguished from ordinary red supergiants because of anomalously high surface abundances of lithium and rp-process elements, produced in the TŻO interior. The TŻO phase ends when either the star has exhausted its rp-process seed elements or the envelope mass decreases below a critical mass (∼14 M⊙). Then nuclear burning becomes inefficient and a neutrino runaway ensues, leading to the dynamical accretion of matter near the core onto the neutron star and its spin up to spin frequencies of up to ∼100 Hz. The fate of the massive envelope is not entirely clear. If a significant fraction can be accreted onto the core, the formation of a black hole becomes likely. Part of the envelope may collapse into a massive disk which may ultimately become gravitationally unstable and lead to the formation of planets or even low-mass stars. We discuss the various possible outcomes and suggest a possible link between massive TŻOs and soft X-ray transients.
A Review of Galactic Millisecond Pulsar Searches
Authors: Lyne A. G.
Published: July 2016

Since the discovery of the first millisecond pulsar in 1982, the main discoveries of more of these exotic objects have come in two bursts. The first followed the realization late in the decade that they might be formed readily in globular clusters and resulted in the discovery of about two dozen objects in these clusters between 1987 and 1990. The second burst started shortly after this as improved computer technology permitted widespread searches of the Galaxy with high sensitivity and is continuing at the present time. This paper describes the main successful surveys for these galactic millisecond pulsars of which 29 are now known. 21 of these are in circular orbits with low-mass companion stars. The large number of objects now available allows a number of firm statistical trends to be seen which all point to an evolutionary phase of these systems involving the spin-up of old neutron stars during the accretion of matter from less evolved companions during their giant phase. Surveys of the present generation are still very insensitive to short period pulsars or highly accelerated pulsars in close or massive binary systems, limitations which should be removed in future years.
Timing Observations of the SMC Binary PSR J0045-7319
Authors: Kaspi V. M. , Manchester R. N. , Bailes M. , Bell J. F.
Published: July 2016

We describe radio timing observations of the binary pulsar PSR J0045-7319 made over the past 3.3 yr. We show that a simple timing model involving a standard Keplerian orbit describes the data well; however, significant low-level systematic residuals never before seen in other binary pulsars remain. We consider various possible origins of the residuals.
Aperiodic Flux Variability in A 0535+262
Authors: Finger Mark H. , Wilson Robert B. , Harmon B. Alan , Paciesas William S.
Published: July 2016

A “giant” outburst of A 0535+262, a transient X-ray binary pulsar, was observed in 1994 February and March with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory. During the outburst power spectra of the hard X-ray flux contained a QPO-like component with a FWHM of approximately 50% of its center frequency. Over the course of the outburst the center frequency rose smoothly from 35 mHz to 70 mHz and then fell to below 40 mHz. We compare this QPO frequency with the neutron star spin-up rate, and discuss the observed correlation in terms of the beat frequency and Keplerian frequency QPO models in conjunction with the Ghosh-Lamb accretion torque model.
Black-Hole Systems: Optical Spectroscopy and IR Photometry
Authors: Charles P.A.
Published: July 2016

The X-ray transient systems have provided the first opportunities for detailed studies of the mass losing star in low-mass X-ray binaries. During X-ray quiescence the cool star is the dominant light source in the red and near-IR. Optical spectroscopy yields the mass function (itself a lower limit to the compact-object mass), the rotational broadening leads to the mass ratio, q (assuming only that the star fills its Roche lobe), and the IR ellipsoidal light curve gives the system inclination (for high q). In such cases, a complete solution to the system parameters is possible, and this has been performed for A 0620-00 (V616 Mon) and GS 2023+338 (V404 Cyg), leading to the first accurate black-hole masses (which are in the range 10–12 M⊙).
Luminous Supersoft X-ray Sources
Authors: Rappaport S. , Stefano R. Di
Published: July 2016

Supersoft X-ray sources exhibit spectra that are remarkably steep, in that the ratio of low-to-high energy X rays is much larger than is characteristic of the spectra associated with the previously known classes of luminous X-ray sources. The first supersoft sources were discovered during a survey of the Large Magellanic Cloud with the EINSTEIN Observatory (Longet al.1981). The all-sky X-ray survey carried out with ROSAT has now established that luminous supersoft X-ray sources constitute a distinct astronomical class (see, e.g., Hasinger 1994). A number of the identified optical counterparts of the supersoft X-ray sources exhibit blue continua with emission lines of H and He II (Smaleet al.1988; Pakullet al.1988; Cowleyet al.1990), which are characteristic of accretion disks. The X-ray emission of some sources is steady, while others exhibit significant time variability. Table 1 briefly summarizes what is known thus far about the numbers and characteristics of supersoft X-ray sources (see Hasinger 1994, and references therein).
Soft Gamma Repeaters Revisited with BATSE
Authors: Kouveliotou C.
Published: July 2016

After the first 4 years of its operation, the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma Ray Observatory (CGRO), detected recurrent emission from two of the three known Soft Gamma Repeater (SGR) sources, SGR 1900+14 and SGR 1806-20. The reactivation of the latter prompted a quick international campaign resulting in the identification of the X-ray counterpart of the source, which also coincides with a compact radio source. The absence of detection of new sources in the 4 years of BATSE operation and the reactivation of two of the three already known SGRs, indicates that these objects are rare. We give here a short review of the previously detected SGR emissions and present the recent results obtained with BATSE.
New Time-distance helioseismology results from the SOI/MDI experiment
Authors: Duvall T.L. , Kosovichev A.G. , Scherrer P.H.
Published: July 2016

The SOI/MDI experiment on SOHO has some unique capabilities for time-distance helioseismology. The great stability of the images observed without benefit of an intervening atmosphere is quite striking. It has made it possible for us to detect the time of flight for separations of points as small as 2.4 Mm in the high-resolution mode of MDI (0.6 arcsec/pixel). This has enabled us to detect the supergranulation flow beneath the surface. Using a tomographic inversion technique, we can now study the 3-dimensional evolution of the flows near the solar surface.
GOLF results: today's view on the solar modes
Authors: Grec G. , Turck-Chièze S. , Lazrek M. , Roca Cortés T. , Bertello L. , Baudin F. , Boumier P. , Charra J. , Fierry-Fraillon D. , Fossat E. , Gabriel A. H. , Garcia R. A. , Gelly B. , Gouiffes C. , Régulo C. , Renaud C. , Robillot J.M. , Ulrich R. K.
Published: July 2016

The SOHO probe was successfully launched on December 2nd, 1995. The performances of the Atlas II flight, the trajectory and the final injection in the Halo orbit around the L1 Lagrangian point left on board a large amount of hydrazine, allowing the possibility for a mission extension later than the 2 planned years. The operations of the GOLF experiment started on January 16th for a period devoted to the initial tests and to the adjustments of the thermal settings. The effective solar observations started on February 18thand are still running. For the studies presented here below, the data set ends in mid-September. All tables and figures come from the compilation of the data analysis made in several institutes with different methods, and some complementary or additional results are displayed in the poster booklet published from this symposium.
The seismic Sun
Authors: Basu Sarbani
Published: July 2016

Helioseismic techniques allow us to probe the interior of the Sun with very high precision and in the process test the physical inputs to stellar models. The picture of the Sun that has been built in this manner may be termed “The Seismic Sun”. After a brief discussion of some of the inversion techniques used in the process, our current view of the seismic Sun shall be reviewed. What we know so far suggests that the internal structure of the Sun can be represented by a standard model, however, one which has a smoother sound-speed and abundance variation than the solar models with the usual treatment of diffusion.
Internal Solar rotation
Authors: Sekii Takashi
Published: July 2016

The rotation of the sun affects the wave propagation in the solar cavity. The measurement of the effect can be used to infer the internal rotation of the sun, and indeed much of what we know today about the dynamics of the solar interior has been derived from observation and interpretation of the rotationally induced splitting of solar p-mode frequencies. Inversion has proven to be a very powerful tool in such investigations, and will remain at the centre of our effort in studying solar rotation from helioseimic data. Study of the flow inside the sun is not only important in its own right but is vital for improving our understanding of solar activity and its cycle. Now that both GONG and SOHO are operational and are accumulating data, there is no doubt that we are about to learn a great deal more about the dynamical structure of our own star.
Long-term solar irradiance variability
Authors: Pap Judit M.
Published: July 2016

Measurements of the solar energy throughout the solar spectrum and understanding its variability provide important information about the physical processes and structural changes in the solar interior and in the solar atmosphere. Solar irradiance measurements (both bolometric and at various wavelengths) over the last two decades have demonstrated that the solar radiative output changes with time as an effect of the waxing and waning solar activity. Although the overall pattern of the long-term variations is similar in the entire spectrum and at various wavelengths, being higher during high solar activity conditions, remarkable differences exist between the magnitude and shape of the observed changes. These differences arise from the different physical conditions in the solar atmosphere where the irradiances are emitted. The aim of this paper is to discuss the solar-cycle-related long-term changes in solar total and UV irradiances. The space-borne irradiance observations are compared to ground-based indices of solar magnetic activity, such as the Photometric Sunspot Index, full disk magnetic flux, and the Mt. Wilson Magnetic Plage Strength Index. Considerable part of the research described in this paper was stimulated by the discussions with the late Philippe Delache, who will always remain in the heart and memory of the author of this paper.
Sounding stellar interiors
Authors: Dziembowski W. A.
Published: July 2016

Multimode pulsations have been discovered in a large variety of main sequence stars and white dwarfs. There are abundant and accurate data on p- and g- mode frequencies in these objects. So far, however, use of these data for sounding interiors has been very limited. The main obstacle is the difficulty in identification of detected modes that is in assignment of spherical harmonic degree, l, azimuthal order, m, and radial order, n, to the modes detected in power spectra of variable stars. This has never been a problem in helioseismology. Even in the case of whole disc measurements a simple structure of power spectra enables an unambiguous mode identification. Such a situation is very rare in asteroseismology. Perhaps oscillating white dwarfs PG 1159-035 and GD 358 are the only examples. Methods of determining the l and m from observational data on the excited modes are available. However, their implementation to – typically low amplitude – multimode pulsators is difficult. In most cases mode identification cannot be separated from determination of stellar parameters.
50 Years of Herbig-Haro Research
Authors: Reipurth Bo , Heathcote Steve
Published: July 2016

We review the events leading to the discovery of Herbig-Haro objects half a century ago, and the early efforts to understand the nature of these enigmatic objects. The recognition in the mid-seventies of the shocked nature of HH objects heralded a burst of observational and theoretical efforts, and further impetus was soon after provided by the discovery of high proper motions, and by detailed optical, infrared and ultraviolet spectroscopic studies. The recognition in the early eighties of HH jets was the starting point for the increasingly intense studies during the last 15 years which we discuss in this Symposium. In the second half of our review, we summarize the insights into the nature of HH jets provided by analyzing high resolution images obtained with the Hubble Space Telescope of two of the finest known HH jets, HH 47 and HH 111.
The Molecular Outflow and CO Bullets in HH111
Authors: Cernicharo J. , Neri R. , Reipurth Bo
Published: July 2016

We present high angular resolution observations of the molecular outflow associated with the optical jet and HH objects of the HH111 system. Interferometric observations in the CO J =2–1 and J =1–0 lines of the high velocity bullets associated with HH111 are presented for the first time. The molecular gas in these high velocity clumps has a moderate kinetic temperature and a mass of a few 10–4 M⊙ per bullet. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.
Shock Chemistry in Bipolar Molecular Outflows
Authors: Bachiller R. , Gutiérrez M. Pérez
Published: July 2016

Chemical studies have a great potential to study the structure and evolution of the bipolar molecular outflows driven by young stellar objects. In this paper, we discuss some very recent mm-wave studies of L 1157, a bipolar molecular outflow driven by a Class 0 protostar. These observations are very useful to illustrate the chemical alterations produced by a violent highly-collimated outflow. Different molecular lines are observed to trace different components of the gas. Some molecules are abundant in the quiescent medium but are not observed in the shock (e.g. C3H2, N2H+, H13CO+, DCO+), whereas some otherwise rare molecules are very enhanced at the shocked region (e.g. SiO, CH3OH, H2CO, HCN, CN, SO, SO2). In addition, we have observed strong gradients in the chemical composition across the outflow blue lobe. We briefly discuss the chemistry of the most important molecules, devoting special attention to the species which are thought to be abundant in interstellar ice mantles.
Hydrodynamic Collimation of YSO Jets
Authors: Frank Adam , Mellema Garrelt
Published: July 2016

We present the results of numerical hydrodynamic models for the collimation of outflows from young stellar objects. We show that the presence of a toroidal environment can lead to efficient formation of jets and bipolar outflows from initially uncollimated central winds. The interaction between the wind and the environment leads to two types of collimation, one which is dominated by radiative cooling effects, and one which works when cooling is less efficient. We describe the two types of jets as they appear in the simulations and we suggest a description for the long term evolution of these structures in more realistic time-dependent wind sources.
Asymmetric Modes of the Kelvin-Helmholtz Instability in Protostellar Jets
Authors: Stone James M.
Published: July 2016

The results of a detailed analysis of the linear properties, nonlinear growth, and saturation of asymmetric modes of the Kelvin-Helmholtz instability in cooling protostellar jet beams are summarized. In the linear regime, cooling can significantly alter the growth rate and wavelength of the most unstable mode in comparison to an adiabatic jet. In the nonlinear regime, sinusoidal oscillations at the maximum growth rate lead to distortions that will be observed as ‘wiggles’ or ‘kinks’ in the jet. Strong cooling behind shocks formed in the nonlinear regime can produce emission knots and filaments. In some cases, the modes grow until the jet is disrupted. Distortions in the surface of the jet drive shock spurs into the ambient gas, resulting in longitudinal acceleration. Rapid acceleration and entrainment of ambient gas is also observed if the jet is disrupted.
Kelvin-Helmholtz Instabilities and the Emission Knots in Herbig-Haro Jets
Authors: Massaglia S. , Micono M. , Ferrari A. , Bodo G. , Rossi P.
Published: July 2016

We discuss the non-linear evolution of Kelvin-Helmholtz instabilities in Herbig-Haro jets performing numerical simulations by means of a PPM hydro-code modified as to include non-equilibrium, optically thin, radiation losses and heating. In this paper we discuss in particular the effects of different functional dependences of heating on density. The results obtained show a weak dependency of the instability evolution on the different forms of the heating function, that is largely unknown, therefore the simple assumption of constant heating, adopted in previous papers on this matter, does not lead to severe limitations on the general applicability of the results to the astrophysical jets and, in particular, to the origin of the emission knots.
Disks and Outflows as seen from the IRAM Interferometer
Authors: Guilloteau S. , Dutrey A. , Gueth F.
Published: July 2016

The IRAM interferometer has been used to map 3 high velocity outflows from Class 0 sources in SiO and CO rotational lines. The images show that such outflows are driven by highly collimated, dense, but optically invisible jets, through large travelling bow shocks. Precession is important in explaining some morphological and kinematic aspects. A significant part of the SiO emission is directly associated with the jet. Images of the molecular core surrounding L 1157 in CO isotopic lines show direct evidence for infall in a large, flattened disk.

For more evolved objects, “surveys” of mm emission from T Tauri stars provide evidence for circumstellar dust disks with relatively flat surface density distribution and typical radii 100 to 200 AU. Much larger gas disks (radii 800 to 1000 AU) have been detected and imaged in a few objects (2 singles and 2 binaries) through CO isotopomers, but in most sources 13CO is difficult to detect. The spectral line images provide unambiguous evidence for Keplerian rotation. In two cases (GG Tau and DM Tau), direct measurements of the gas mass (independently of the dust) has been made thanks to the detection of 7 molecular species. The molecules are found to be depleted by factors between 5 (for CO) to 100 (for H2CO). These results suggest that circumstellar disks consist in a small, dense, inner disk of outer radius ≃ 150AU (traced by the dust emission), surrounded by a much larger, less massive, outer disk (traced by the gas emission).
Thermal Structure of Magnetic Funnel Flows
Authors: Martin Steven C.
Published: July 2016

The thermodynamic structure of gas that is channeled by stellar magnetic fields onto a young (pre–main-sequence) star is presented. In this model, the star possesses a dipole magnetic field which disrupts the inner regions of a geometrically thin accretion disk and channels the inflowing gas onto the stellar surface, thereby forming an accretion funnel. The temperature and ionization degree of the inflowing gas is calculated by solving the heat equation coupled to statistical rate equations for hydrogen. It is found that for typical accretion rates of ∼ 10–7M⊘yr–1, temperatures of ∼ 7000 K and hydrogen ionization fractions (nH+/nH) of ∼ 10–2 can be attained in the funnel flow. The principal heat source is found to be adiabatic compression, and coolants include bremsstrahlung radiation as well as line emission from the Ca II and Mg II ions. The relatively hot and ionized funnel flow lead to observational signatures such as inverse P Cygni line profiles seen in upper Balmer and near-infrared lines. In addition, carbon monoxide bandhead emission may be an important tracer of the outer portions of the funnel flow.
Orion Proplyds and The Eagle's Eggs
Authors: McCaughrean Mark
Published: July 2016

We describe the effects of environment on low-mass star formation, from the perspective that most stars in the galaxy form in dense clusters and aggregates in GMCs, often in the presence of massive OB stars. First, we discuss the observational evidence for circumstellar disks around stars of the Trapezium Cluster, and how they are affected by their environment. Second, we examine the more distant M 16, where photo-evaporation by OB stars may disrupt the star formation process, and may inhibit the development of circumstellar disks.
Statistical Investigation of Spectroscopic Binary Stars
Authors: Tutukov A. V. , Yungelson L. R.
Published: July 2016

A catalog of physical parameters of about 1000 spectroscopic binary stars (SB), based on the Batten catalog, its extensions, and newly published data has been compiled. Masses of stars′ components (M1 and M2), mass ratios of components (q = M1/M2) and orbital angular momenta are computed, wherever possible. It is probable that the initial mass function of the primaries is non-monotonic and is described only approximately by a power-law. The distribution of q of double-line SB has a sharp maximum near q = 1, that of single-line SB, near q = 0.3. SB with 1.5 ≲ M1/M⊙ ≲ 10 and semiaxes of orbits a ≲ 10 R⊙ probably do not form. A number of assumed “initial” distributions of M1, q and a were transformed with the aim of obtaining “observed” distributions taking into account the observational selection due to the luminosities of the components, their radial velocities, inclinations of the orbits, and the effects of matter exchange between the components. The best agreement with the observations is obtained for the combination of a power-law initial mass function ξ(M) ≃ M−2.35, a distribution of q with a maximum near 1 and a distribution of semiaxes with dN/da ≃ 1/a.
Ultraviolet Spectroscopy of Binary Systems
Authors: Dupree A. K. , Hartmann L. , Raymond J. C.
Published: July 2016

The recent launch of the International Ultraviolet Explorer (IUE) satellite and its spectrographic instruments (Boggess et al. 1978a,b) suddenly made accessible large numbers of diverse types of binary systems. These range from the luminous hot supergiants with compact companions that produce copious amounts of X-rays to the dwarf solar like stars of W UMa-type. For systems such as these and many others the IUE is a new and unique tool with which to probe the structure of extended stellar atmospheres, the presence and acceleration of a stellar wind, and the appearance of stellar chromospheres and coronae.
Close Binaries Before and After Mass Exchange: A Comparison of Observations through Theoretical Computations
Authors: De Grève J. P. , Vanbeveren D.
Published: July 2016

From a search through the literature 174 close binaries with completely known absolute dimensions are sampled. Distinction is made between systems before and after mass exchange, giving resp. 100 and 40 systems (a third group contains the systems not definitely belonging to these two). Mass, period and mass ratio distributions and relations of the group of “unevolved” binaries (i.e. prior to mass exchange) are transformed into corresponding distributions and relations of evolved binaries. The transformations are based upon the M1 f = g (M1 i) relation derived from an extended set of published theoretical computations on the evolution of close binaries. Final masses resulting from the same initial mass are averaged. Equations are derived for the cases A (for all masses), B1 (M1 i/Mo < 2.8), B2 (2.8 < M1 i/Mo < 9) and B3 (M1 i/Mo > 9). For the changes of the period due to angular momentum loss the formalism of Vanbeveren et al. (1979) was adopted. The following characteristics of the system after mass exchange are computed: M1 f, M2 f (and qf), Pf. Three different modes were applied for the mass loss from the system:

a) conservative case (mass and angular momentum of the system remain constant), called C.

b) non conservative case with 50% of the transferred mass leaving the system with a small or a large angular momentum loss (resp. called NC51 and NC53).

c) non conservative case with 100% of the transferred mass leaving the system with a small or a large angular momentum loss (resp. called NC101 and NC103).
The Evolution of Massive Close Binary Systems : Estimates of the Parameters Governing Mass and Angular Momentum Loss
Authors: Vanbeveren D. , De Loore C.
Published: July 2016

It becomes more and more evident that for close binary evolution during Roche lobe overflow as well mass transfer as mass loss occurs. When a mass element ΔM is expelled from the primary during this phase, a fraction β is transferred to the secondary; the remaining part leaves the system. Moreover, angular momentum leaves the system, and also this fraction has to be specified; this fraction is related to a parameter α (Vanbeveren et al., 1979). For the computation of the evolution of massive close binaries also mass loss due to stellar wind of both components, prior to the Roche lobe overflow has to be taken into account. The mass loss rate Ṁ due to radiation driven stellar winds can be expressed as
Mass Transfer between Binary Stars
Authors: Modisette Jerry L. , Kondo Youi
Published: July 2016

The transfer of mass from one component of a binary system to its companion can involve ejection of the mass by radiation pressure, by Roche lobe overflow, by centrifugal action through the coupling of the upper atmosphere to the stellar rotation through magnetic fields, and by the dynamics of the atmospheric fluid under the action of an energy source at the photosphere or lower chromosphere. We will primarily address the latter mechanism, which commonly goes under the title of stellar winds. The major determinant of a stellar wind is the energy source. In the case of a binary system, the dynamic effects of the system on the flow pattern, particularly for close binaries, is a second major determinant, once an energy source is available to drive the wind. Roche lobe overflow might be thought of as a limiting case in which the system dynamics predominate.
Transient Disks and Mass Transfer in U Cephei
Authors: Olson Edward C.
Published: July 2016

Conspicuous, variable photometric contamination was observed during primary eclipses of the totally eclipsing Algol-like system U Cep from late-1974 to late-1977. Excess light was particularly prominent between second and third contacts, and originated mainly in optically thick accretion disks surrounding the B-type hot component. Observations of such disks were obtained with uvby (I) photometry during 10 eclipses, using the 1.0 M and 0.4 M reflectors at Prairie and Kitt Peak National Observatories. Figure 1 shows ultraviolet observations between internal contacts for active (October, 1975) and quiescent eclipses. The light excess over quiescent levels was converted to flux distributions Lλc relative to the quiescent visual flux of. the G-star.
The Star Spot Model and the Observations of SZ Piscium
Authors: Jakate Shyam M.
Published: July 2016

Details of photometric observations during the totalities of the primary and secondary minima of SZ Psc are analysed in the light of the “star spot model” for RS CVn type binaries. Presence of scatter during the totality of primary minimum and its absence during the totality of secondary minimum of SZ Psc provide evidence towards one of the assumptions of the model,i.e. the spot activity confines to one of the hemispheres of the cooler star.
Circumstellar Material in Cataclysmic Binaries
Authors: Smak J.
Published: July 2016

This semi-review will concentrate primarily on geometric and photometric parameters of rotating gaseous disks in cataclysmic binaries. Dimensions, or more precisely - the outer radius of the disk can be estimated from three types of data: (a) From the analysis of eclipses of the hot spot, by assuming that its “radius-vector” is identical with the outer radius of the disk. (b) From the analysis of the eclipses of the disk itself. (c) From the radial velocity data giving the rotational velocity of the disk and the orbital velocity(ies) of the component(s). The resulting radius, corresponding to the peaks of the double emission lines, is not identical but presumably quite close to the outer radius of the disk. From a more detailed analysis of the disk's eclipse one can also obtain an information concerning the surface brightness distribution across the disk.
The Cyclotron Lines in the Optical Spectra of the Stars of AM Herculis Group: Observations and Interpretation
Authors: Mitrofanov I. G.
Published: July 2016

The stars of the AM Herculis group (AM Her, VV Pup, AN UMa and 2A 0311-227) are close binaries containing a mass losing, nondegenerate star and an accreting degenerate dwarf. Their main properties are: the large linear and circular polarization of the optical light, high and low luminosity states, the variable emission line, spectra of H, He and other elements and the identification of these objects with X-ray sources. It is generally accepted that the strong magnetic field of the degenerate dwarf is responsible for these peculiar properties and for the distinction between these objects and the cataclysmic variables (Mitrofanov 1978, 1979a). The polarized optical continuum may be emitted by the accreted magnetized plasma (e.g. Chanmugam and Wagner, 1979), by the magnetized photosphere of the degenerate dwarf (Mitrofanov et al. 1977), or by both sources (Mitrofanov, 1979b). To explain the observed X-rays, Lamb and Masters (1979) showed that a magnetic field about 108 gs is necessary. Unfortunately, the basic prediction of their model - the strong ultraviolet continuum in the spectrum of AM Herculis - appears to be absent (Raymond et al. 1979). Chanmugam and Wagner (1979) proposed a rather different estimate for B of 2 · 108/m*gs (m* = 5 ÷ 25). For further investigations of the AM Herculis-type stars it seems useful to find a direct observational method for measuring the dwarfs′ magnetic fields.
Close Binary Systems in Globular Clusters: A Preliminary Report
Authors: Webbink R. F.
Published: July 2016

A brief survey of known eclipsing binaries and cataclysmic variables in globular cluster fields is presented. None of the 47 known or suspected eclipsing variables is a promising candidate, although a very few remain possible members. V101 in M5 is a good candidate for membership, among 5 known or suspected dwarf novae. Three novae have been discovered in globular cluster fields, of which two are almost certainly members. Attention is also called to the eclipsing binary V80, a system which appears to contain an RRc variable, in the dwarf spheroidal galaxy in Ursa Minor.
Les effets de la refraction atmospherique sur les coordonnees tangentielles en astrometrie
Authors: Dommanget J.
Published: July 2016

The astrometric plate reduction needs the knowledge of formulae expressing the transformation of the configuration of stellar positions on the celestial sphere into the corresponding observed figure of the photographic images on the plate. This transformation includes phenomena such as the atmospheric refraction, the optical distortion, the plate position on the instrument, etc. of which the relative importance may vary from one case to another and may lead thus to various formulae.
On the characteristics of astronomical refraction in the northern hemisphere
Authors: Sugawa C. , Kikuchi N.
Published: July 2016

The astronomical refraction mainly depends on the vertical structure or the height profile of atmospheric density. Concerning the vertical structure of atmospheric density, various hypotheses were presented during the last century. Among them Newton's hypothesis of equal temperature and Ivory's one that temperature diminishes at a uniform rate with height appear to represent the height profile of temperature approximately in the lower part of the stratosphere and in the troposphere respectively.
Astronomical refraction at the Mizusawa Latitude Observatory
Authors: Takagi Shigetsugu , Goto Yukio
Published: July 2016

The formulation to calculate the precise refraction by means of the primitive equations by an electronic computer was made to be used for the calculation of the atmospheric refraction in the astrometry and the satellite geodesy with upper air data obtained with the atmospheric soundings.
Diurnal changes of radio refraction
Authors: Altenhoff Wilhelm J.
Published: July 2016

Pathlength variations due to refraction changes in the troposphere may impose a severe limitation to VLB experiments (like random clock drifts). In connection with a VLB experiment Moran and Penfield (1976) analysed surface values of water vapor density, data of several hundred radiosonde launches and of measurements of sky brightness near the water vapor line at λ = 1.3 cm. They found that the surface values allow to estimate the pathlength to an accuracy of 5 cm in summer and 2 cm in winter. Sky brightness data give a prediction accuracy of 1.5 cm for all weather conditions, but for cloudfree conditions the accuracy was 0.3 cm.
Results from an absolute test of the NPL dispersometer over 4 km
Authors: Williams D. C.
Published: July 2016

The NPL instrument to correct for angular refraction in geodesy measures the small dispersion between images of red (633 nm) and blue (442 nm) laser sources formed by a telescope. It uses a rotating chopper disc in association with an optical compensator plate and a phase null meter. The instrument and some early field tests have been described in detail elsewhere (Williams, D.C., 1978).

Absolute tests of the prototype have recently been made over a 4 km suburban range at an average height of 30 m. The apparent elevation of the red laser was observed with a T3 theodolite and corrected for refraction, the laser and theodolite being referred to local bench marks with a known height difference determined by spirit levelling.

On an occasion in late May 1978, the effects of turbulence were particularly small. The refraction-corrected theodolite readings then agreed with the expected value to within one sexagesimal second. Other results obtained during the preceding two months indicate that increasing turbulence causes the dispersion angle to appear too large, the greatest error observed being about 3 seconds of refraction. It is thought that most of the turbulence was due to effluent from chimneys, and that the apparent error may be due to an instrumental effect which has not yet been identified.

The performance of the instrument has also been evaluated on a 20 km range near Uppsala during the present Symposium, by kind invitation of Prof. E. Tengström. The principal difference from the 4 km range was that the intensity scintillations of the red and blue signals were no longer correlated when the refraction was large. Independent compensation of red and blue signals for this effect should enable good results to be obtained over this distance.

The author wishes to acknowledge the help of S-G. Mårtensson and S. Eklund (University of Uppsala) and A.J. Griffiths (NPL) in performing the tests.
Experiences from IDM measurements at the test base of the Geodetic Institute of Uppsala University
Authors: Mårtensson S-G.
Published: July 2016

IDM measurements carried out in Uppsala sometimes show violent changes in refraction over short periods of time.

The explanation for these changes might be found if the dynamics of atmospheric turbulence is taken into consideration.

It is too early to make scientific conclusions from the material collected so far, but observations show the way this particular problem can be handled in the future.

The paper presented, reflects some of the turbulence effects achieved by the IDM instrument constructed by prof. E. Tengström.
Inversion of the Zodiacal Brightness Integral: a new Geometric Approach Suitable for the Out-Of-Ecliptic Zodiacal Light Programme
Authors: Dumont René , Levasseur-Regourd Anny-Chantal
Published: July 2016

The information provided by measurements of the zodiacal brightness, Z, is discussed as a function of the looking direction, with respect to the velocity vector of the observer through the solar system. In addition to a few directions which allow inversion of the brightness integral completely free of assumptions, it is shown that the orbital plane gives inverting possibilities, based on a single assumption on the heliocentric dependence of the volume scattering efficiency. Important features of the zodiacal cloud distribution, very difficult to obtain from earthbound observations, will easily be derived from the data of the Out-Of-Ecliptic Zodiacal Light Experiment.
The Analysis of Meteor Data
Authors: Baggaley W. J.
Published: July 2016

A problem commonly encountered in meteor studies is the need for a realistic interpretation of statistical data which contains uncertainties in two variables. A simple solution is provided and for illustration applied to diffusion-height data.
Correlation of Height and Forbidden Oxygen Line Strength for Perseid Meteors
Authors: Russell John A.
Published: July 2016

During the 1977 and 1978 Perseid showers, seventeen meteors were simultaneously photographed with a spectrograph and with a camera equipped with a rotating shutter. Of the eight best examples, the half in whose spectra the forbidden line of neutral oxygen at λ5577 was relatively strongest appeared and disappeared at heights about 9 km. greater than did the half in whose spectra the line at λ5577 was relatively weak. Structural or compositional differences in the meteoroidal particles appear to be the most likely explanation for these height variations. A by-product of the investigation was an average value of −8.8 km/sec2 for the deceleration of the meteors over the observed trajectories.