bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Organic Matter Decomposition and Turnover in a Tropical Ultisol: Evidence from δ13C, δ15N and Geochemistry
Authors: Krull Evelyn S , Bestland Erick A , Gates Will P
Published: July 2016

Soil organic matter (SOM), leaf litter, and root material of an Ultisol from the tropical rainforest of Kakamega, Kenya, were analyzed for stable carbon (δ13C) and nitrogen (δ15N) isotopic values as well as total organic carbon (TOC) and total nitrogen (TN) contents in order to determine trends in SOM decomposition within a very well-developed soil under tropical conditions. In addition, we quantified mineralogy and chemistry of the inorganic soil fraction. Clay mineralogical variation with depth was small and the abundance of kaolin indicates intense weathering and pedoturbation under humid tropical conditions. The soil chemistry was dominated by silica, aluminium, and iron with calcium, potassium, and magnesium as minor constituents. The relative depletion of base cations compared with silica and aluminium is an indicator for intense weathering and leaching conditions over long periods of time. Depth profiles of δ13C and δ15N showed a distinct enrichment trend down profile with a large (average 13δC = 5.0 and average 15δN= 6.3) and abrupt offset within the uppermost 10–20 cm of the soil. Isotopic enrichment with depth is commonly observed in soil profiles and has been attributed to fractionation during decomposition. However, isotopic offsets within soil profiles that exceed 3 are usually interpreted as a recent change from C4 to C3 dominated vegetation. We argue that the observed isotopic depth profiles along with data from mineralogy and chemistry of the inorganic fraction from the Kakamega Forest soil are a result of intense weathering and high organic matter turnover rates under humid tropical conditions.
Ingeis Radiocarbon Laboratory Dates IV
Authors: Cordero Roberto , Lanzelotti Sonia , Panarello Héctor
Published: July 2016

We present here the results of dating of 80 archaeological and paleoenvironmental samples from Argentina and Uruguay, processed between 1986 and 1988 by M A Albero and M A Gonzalez. Series of samples and single samples are grouped by province and then by locality or archeological site, from north to south. See sample location maps for details.

Procedures for sample pretreatment, counting, statistical analysis, and age calculation were essentially the same as previously described by Albero and Angiolini (1985). Results are reported as conventional 14C dates in years before AD 1950. They are corrected for isotopic fractionation. 14C contents of some paleoenvironmental samples are expressed in percent modern carbon (pMC).
Why Early-Historical Radiocarbon Dates Downwind from the Mediterranean are Too Early
Authors: Keenan Douglas J
Published: July 2016

Several authors have claimed that radiocarbon dates in the Ancient Near East are too early. Herein, a hypothesis that might explain this is presented. Marine degassing of “old” carbon (i.e.14C-deficient C), induced by upwelling of old subsurface water, has been observed, in modern times, to cause century-scale14C ages in the surface atmosphere. A review of the Mediterranean Sea post-ice-age circulation concludes that the subsurface waters became very old, primarily due to millennia-long stagnation. It is hypothesized that as the stagnation ended, subsurface waters were brought towards the surface, where they degassed old carbon. Additionally, Anatolian dendrochronology is shown to not contradict the hypothesis.
AMS Radiocarbon Dating of Ancient Bone Using Ultrafiltration
Authors: Higham T F G , Jacobi R M , Ramsey C Bronk
Published: July 2016

The Oxford Radiocarbon Accelerator Unit (ORAU) has used an ultrafiltration protocol to further purify gelatin from archaeological bone since 2000. In this paper, the methodology is described, and it is shown that, in many instances, ultrafiltration successfully removes low molecular weight contaminants that less rigorous methods may not. These contaminants can sometimes be of a different radiocarbon age and, unless removed, may produce erroneous determinations, particularly when one is dating bones greater than 2 to 3 half-lives of 14C and the contaminants are of modern age. Results of the redating of bone of Late Middle and Early Upper Paleolithic age from the British Isles and Europe suggest that we may need to look again at the traditional chronology for these periods.
Seoul National University Accelerator Mass Spectrometry (SNU-AMS) Radiocarbon Date List II
Authors: Kim J C , Youn M Y , Kim I C , Park J H , Song Y M , Kang J , Cheoun M K
Published: July 2016

The accelerator mass spectrometry facility at Seoul National University (SNU-AMS) began functioning in December 1998 and was first reported at the Vienna AMS conference in October 1999 and at the 17th Radiocarbon Conference in Israel in June 2000. At the Vienna conference, we reported our accelerator system (Kim et al. 2000) and the basic sample preparation system (Lee et al. 2000), including the combustion line to produce CO2; the catalytic reduction line for the graphitization of CO2; and also pretreatment procedures for wood, charcoal, and peat samples. Recent progress of the AMS facility (Kim et al. 2001) and extension of the sample pretreatment system to iron and bone samples were reported at the 17th Radiocarbon Conference (Cheoun et al. 2001). In the meantime, extensive testing of accuracy and reproducibility has been carried out, and ∼1000 unknown archaeological and geological samples have been measured every year. A report of data carried out in 1999 is presented by Kim et al. (this issue). In this report, the archaeological, geological, and environmental data carried out in 2000 are presented in terms of yr BP.
The Gale–Pruss cosmological argument:TractarianandadvaitaHindu objections
Authors: McDONOUGH RICHARD
Published: July 2016

The article criticizes Gale and Pruss's new cosmological argument (hereafter GP) which purports to prove that the world is created/designed by a powerful intelligent necessarily existing supernatural being (not the full-fledged God of theism). First, the article employs a ‘necessitist’ counterexample to GP's modal premise, S5. Second, it is argued that GP presupposes a restricted range of possible accounts of the generation of the universe. Third, it is argued that GP's argument that the creator is a necessary being is flawed. Fourth, it is argued that GP's argument against Quinn's objection, modelled on theadvaitaHindu view of creation by an impersonal being, also fails.
The Social Life of the Performer on the Yorkshire Circuit, 1766–1785
Authors: McDonald Arthur W.
Published: July 2016

In the second half of the eighteenth century many members of English provincial theatre companies acquired a high level of social acceptability. Influential citizens ranging from the aristocracy to the military and from the high sheriff to members of various social and civic clubs began to lend their patronage to country theatre performances and to particular performers. “So they became quite respectable members of local society … [and their] old reputations as shiftless and untrustworthy fitted only the poorest members of the profession.”
Angular momenta of late-type spiral galaxies
Authors: Heidmann N.
Published: July 2016

The angular momenta of galaxies may be evaluated from their photometry. The mass to light ratio in NGC 224 is discussed and the calculation is applied to two late-type spirals.
Applying the model of a normal logarithmic spiral to galaxies
Authors: Dzigvashvili R. M. , Borchkhadze T. M.
Published: July 2016

The characteristic μ angles for the spirals of 6 multi-arm galaxies (NGC 1232, 5247, 4303, 4321, 3938, 3184) have been determined. It has been found that they vary along spiral arms within a rather large interval, with mean square deviations ranging from 4° to 20°. The mean μ for each arm deviates in a relatively small degree from the mean μ of the whole galaxy.

The authors apply the normal logarithmic spiral model in estimating the number of arms in our Galaxy. On the basis of this model the number of spiral arms for the above galaxies have been determined and compared with the actual number. It is shown that the normal logarithmic spiral model is unsuitable for our purposes. The number of spiral arms calculated in this way is not reliable.
OB stars on the outermost borders of M31
Authors: Börngen F. , Friedrich G. , Lenk G. , Richter L. , Richter N.
Published: July 2016

Van den Bergh (1964) has selected and mapped OB associations in M 31 on the basis of plates taken with the Tautenburg 52 inch Schmidt camera. The selection was done by the blinking method. The task of the present investigation is to find if there exist OB stars (single or in association) on the outermost borders of this stellar system. For this purpose we measured the brightness of all stellar objects in UBV down to the magnitude 20m.0 (B) on Tautenburg plates in a special test field (Figure 1). It includes 0.26 square degrees and its centre has a distance of 104′ = 22 kpc from the centre of M 31. This test field includes too Baade's field IV with the photoelectric standards in UBV observed by Arp (Baade and Swope, 1963) and the OB associations OB 184, OB 185 and OB 186 of Van den Bergh. The total number of stars brighter than 20m.0 (B) was 996. The stars within the associations OB 184 and OB 185 are not included in these statistics. From this number, 704 objects could be measured in all 3 colours. We found among them 23 blue objects with U–B ≤ U− ≤ −0m.25. The mean error of the brightness on the basis of 4 plates in each colour does not exceed ±0m.0.7 for stars of 19m.0 (B).
Radial velocities of neutral hydrogen in the anticenter region of the Galaxy
Authors: Velden L.
Published: July 2016

An observational material of 21-cm H I emission-line profiles is investigated by a statistical method to derive the kinematical properties of the interstellar gas in the region of the galactic anticenter. A description of the method used as well as the results obtained, concerning deviations from a circular rotation, are given.
The distribution in galactic longitude of observable pulsars
Authors: Lyngå G.
Published: July 2016

I have studied the galactic longitude distribution of low latitude pulsars on the assumption that pulsars are evenly distributed in the galactic disk but that their observability is severely impaired by spiral features, rich in H II regions, in which the high electron density causes a high dispersion measure for a comparatively short optical path. The assumption of even distribution in the galactic disk seems natural as no correlation between positions of pulsars and spiral tracers is known, and since supernovae in external galaxies are not known to confine to spiral arms.
A comparison of the density gradients of main sequence stars obtained by two different methods in different galactic latitudes
Authors: Becker W. , Fenkart R.
Published: July 2016

The Basel Observatory program of the determination of disc- and halo-density gradients for different intervals of absolute magnitude comprises in addition to Milky Way fields several directions, all pointing to Selected Areas near a plane perpendicular to the galactic equator and passing through the sun and the galactic centre. It was started with SA 51 (Becker, 1965) and continued with Sa 57, 54 and 141 (Fenkart, 1967, 1968, 1969).
The space distribution of the OB-type stars in Carina
Authors: Graham J. A.
Published: July 2016

Distances have been determined for 436 OB-type stars in Carina. A sharp outside edge is found to the OB star distribution with respect to the center of the Galaxy. The layer of OB stars follows the galactic plane to distances of the order of 3 kpc, but at distances greater than 4 kpc it appears to bend away from the plane to negative latitudes by 2° or 3° out to distances of the order of 10 kpc.
Calibration of 4-color and Hβ photometry for B- and A-type stars
Authors: Crawford D. L.
Published: July 2016

Observing has been underway for several years, at Kitt Peak and Cerro Tololo, of the bright B and A stars, and of the brighter and nearer open clusters, to supply data necessary for calibration of 4-color and Hβ indices in terms of intrinsic color and absolute magnitude, as well as for use in studies of galactic structure. To date, data are on hand – some published, most being prepared for publication – for all O- to G0-type stars brighter than V = 5m.0, for most O- to B5-type to 6m.5, and for most northern hemisphere O- to G0-type to 6m.5. In addition, the following open clusters have been studied: Hyades, Coma, Ursa Major, Praesepe, α Persei, Pleiades, IC 2602, IC 2391, h and χ Persei, NGC 6231, NGC 752, and IC 4665.
Wolf-Rayet stars, ring-type H II regions, and spiral structure
Authors: Schmidt-Kaler Th.
Published: July 2016

At the Prague IAU meeting (Isserstedt and Schmidt-Kaler, 1967) we presented some results of investigations on stellar rings, a new kind of stellar association and powerful spiral tracer. We have since kept looking for similar features of gas or dust which might be early stages in the evolution of stellar rings.
Radial velocities of early-type stars
Authors: Kaufmann J. P.
Published: July 2016

With the Fehrenbach objective prism radial velocities of about 700 stars of type B0 to A0 were determined in two fields of the Southern Milky Way (lII = 295° bII = −0.6°; lII = 320° bII = −2.5°), with a mean error of ±20 km s−1. An additional photographic UBV-photometry with plates of the ADH-telescope at Boyden Observatory was accomplished. Minimum distances for the stars resulted from absorption-corrected magnitudes and a MK-spectral classification. About 200 stars lay at distances greater than 1.5 kpc from the sun. The largest distances determined were 5 kpc. From the radial velocities and distances circular velocities were derived and plotted against galactocentric distances R. Even within the possible error limits a positive velocity gradient showed up in the range 8 kpc < R < 9.5 kpc, which French authors had already found for the region 10.5 kpc < R < 12.5 kpc. If there do not exist significant deviations from circular motion for these stars, a conformity with Schmidt's 1965 model cannot be obtained.
Structure and dynamics of barred spiral galaxies with an asymmetric mass distribution
Authors: De Vaucouleurs G. , Freeman K. C.
Published: July 2016

The asymmetric structure and dynamics of late-type barred spirals is analyzed in terms of a model consisting of a small prolate spheroid (the bar) displaced from the center of a large oblate spheroid (the disk). The non-axisymmetric motions predicted for this model are in remarkable agreement with optical and radio observations of internal motions in several magellanic barred spirals, including NGC 4027 and the Large Cloud. In particular, the model explains the displacement of the apparent center of the rotation curve from the center of the bar.
Interpretation of large-scale spiral structure
Authors: Lin C. C.
Published: July 2016

The present paper consists of three parts: (1) A general explanation, from a semi-empirical point of view, of the density wave theory and its ramifications, with only a few remarks on those detailed features which have not been stressed before; (2) a statement of our conclusions about the Milky Way System; and (3) a discussion of the problem of the origin of density waves of spiral form.
Theoretical 21-cm line profiles: Comparison with observations
Authors: Yuan C.
Published: July 2016

In order to make a direct comparison with observations of the 21-cm line of neutral hydrogen, theoretical profiles based on the ideas of the density-wave theory are constructed for a modified Schmidt model of the Galaxy and its theoretical spiral pattern. The comparison has covered galactic longitudes lII = 30° −330° with 10° intervals in the galactic plane. Good agreement is found in most of the above directions.
On the circulation of gas near the galactic center
Authors: Spiegel E. A.
Published: July 2016

A model of a quasi-steady circulation of gas near the galactic center is considered to explain the outward motion of the 3-kpc arm. A hydromagnetic wind from the galactic nucleus reaches the 3-kpc arm, where a shock is formed; then the gas moves out of the plane and eventually returns to the nucleus. The secular behavior of the model is discussed.
Magnetohydrodynamical models of helical magnetic fields in spiral arms
Authors: Fujimoto M. , Miyamoto M.
Published: July 2016

A circular arm with elliptical cross-section is used as a model of the spiral arm. It is demonstrated magnetohydrodynamically that interstellar gas may flow in a helical path along the axis of the arm and interstellar helical magnetic lines of force can spiral around it. It is pointed out that though the rolling motions of gas do not always indicate the existence of the helical magnetic field, the latter cannot be in a stationary state without the former. Some observational supports to the present model are given.
Searches for Cataclysmic Variables in Globular Cluster Cores
Authors: Shara Michael M.
Published: July 2016

Close binaries are widely believed to exist in large numbers in the cores of globular clusters. If present, these binaries are critical sources and sinks of energy that drive the dynamical evolution of their host clusters. I report on HST searches for binaries (based on variability) in the outskirts and cores of several globular clusters; dwarf novae should be particularly easy to find. Dense and loose clusters have been thoroughly searched on timescales ranging from minutes to years. Detailed simulations demonstrate that virtually all binaries with M < 8, amplitudes > 0.1 mag and periods of 2–20 hours should have been found. This includes virtually all known contact binaries. At least 1/3 of all dwarf novae present in several globulars should also have been seen (very easily!) in eruption at M = 4 − 6.

Simple tidal capture theory predicts that dozens of interacting binaries should have been found in our searches; the observed number is typically one or two objects per cluster. Unless tidal capture cataclysmic binaries are rapidly destroyed, ejected, or much fainter than most of their Galactic counterparts, we must conclude that very close binaries in globular cores are rare, and that their total influence on cluster dynamical evolution is less than currently claimed.
The Centers of Galaxies
Authors: Richstone Douglas , Gebhardt Karl , Dressler Alan , Faber Sandra , Grillmair Carl , Kormendy John , Byun Y.-I. , Lauer Tod , Ajhar Edward , Tremaine Scott
Published: July 2016

This report has two major purposes. First, we summarize here work by our team on the determination of the density of stars near the centers of a large sample of galaxies observed with the Hubble Space Telescope. There appear to be two varieties of elliptical galaxies (and bulges). The stellar densities near the centers of small elliptical galaxies exceed those of globular clusters and the density of the universe at the recombination epoch. The radial dependence of density and implied gravitational force seems inconsistent (at least in the case of the smaller elliptical galaxies) with a long-lived triaxial configuration. It therefore seems likely that the central regions of less luminous elliptical galaxies are axisymmetric. For the more luminous ellipticals, the central densities are far more modest and the presence of a distinct core (defined below) is generally well established. Even in these cases, however, we find few if any galaxies with analytic (Taylor expandable) stellar densities near the center.
The Nuclear Star Cluster of the Milky Way: Star Formation, Stellar Collisions and Central Dark Mass
Authors: Genzel R.
Published: July 2016

High resolution near-infrared imaging and spectroscopy now gives detailed information about the structure, evolution and mass distribution in the nuclear star cluster of the Milky Way. The central parsec is powered by a cluster of luminous and helium rich, blue supergiants/Wolf-Rayet stars. The most likely scenario for the formation of the massive stars is a star formation burst a few million years ago at which time a dense gas cloud may have fallen into the center. The stellar density in the ∼ 0.3 pc radius central core is high enough that collisions with main sequence stars destroy the largest late type giant stars. Radial velocity measurements for about 300 early and late type stars between 0.1 and 5pc radius from the dynamic center now strongly favor the existence of a central dark mass of 2.5 − 3.3 × 106M⊙ (density (109M⊙pc−3, M/L2μm) ∼ 100M⊙/L⊙) within 0.1pc of the dynamic center. This central dark mass cannot be a cluster of neutron stars. It is either a compact cluster of stellar black holes or, most likely, a single massive black hole.
Fluid Techniques and Evolution of Anisotropy
Authors: Spurzem Rainer
Published: July 2016

Fluid dynamical techniques to model the dynamical evolution of star clusters, and their successors, gaseous models using an equation of heat conductivity to model relaxation effects, including anisotropy, are presented. The historical merits of such models are reviewed as well as the current status of their credibility, based on quantitative comparisons with other methods, like orbit-averaged Fokker-Planck solutions and direct N-body simulations.
SPH Calculations of Collisions Between Main-Sequence Stars
Authors: Rasio Frederic A.
Published: July 2016

The hydrodynamics of collisions and mergers of main-sequence stars is discussed in the light of recent 3-D calculations using the smoothed particle hydrodynamics (SPH) method. Theoretical models for the formation of blue stragglers are reviewed in the context of recent comparisons between the observed properties of blue stragglers in dense globular clusters and the predictions of those models.
Tidal Capture in Star Clusters
Authors: Mardling Rosemary A.
Published: July 2016

We review the tidal capture process and in particular the chaotic orbital evolution which follows capture. We discuss the formation of low-mass X-ray binaries in globular clusters via tidal capture and speculate on the possibility that some field low-mass X-ray binaries were formed this way in open clusters which have since dispersed, or in existing old open clusters which are not accessible to observation because of obscuration by dust or because they are indistinguishable from the rich background of galactic stars.
CCD Photometry of the Open Cluster BE 69
Authors: Pandey A.K. , Durgapal A.K. , Bhatt B.C. , Mohan Vijay , Mahra H.S.
Published: July 2016

The morphological features of CMDs of Be 69 are better understood in terms of convective overshooting. The comparison of CMDs with the convective overshoot models (Bertelli et al. 1994) produces a good fit for a metallicity Z=0.008, age = 0.8 − 1.0 billion yr and (m-M) = 14.3, which corresponds to a distance of 2860 pc.
Pal 1: Another Young Globular Cluster?
Authors: Rosenberg A. , Saviane I. , Piotto G. , Zaggia S. , Aparicio A.
Published: July 2016

We present a color magnitude diagram (CMD) in the V and I bands reaching ∼ 4 magnitudes below the turn off (TO) for the galactic globular (?) cluster Pal 1. A comparison with other well-observed clusters and theoretical models suggests that Pal 1 has an age of 8±2 Gyrs, which would make it the youngest globular cluster of our Galaxy.
Binary-Single Encounters of 10 M⊙ Black Holes Including the Effects of Gravitational Radiation
Authors: Kong K. N. , Lee H. M.
Published: July 2016

We compute the outcomes of close encounters between a binary and a single black holes including the effects of gravitational radiation reaction. All masses of individual black holes are assumed to be 1 M⊙. We found that merger of two black holes takes place during the encounters in some cases. Thus the gravitational radiation can act as a mechanism for the dissipation of energy of a cluster mainly composed of 10 M⊙ black holes which are produced by the evolution of high mass stars. The merger probability depends on many parameters in a complex way. Our preliminary calculations show that about 10% of the strong encounters (i.e., rp ∼ a) between a binary of hardness 100 and a single lead to mergers of two black holes in the stellar system of one-dimensional velocity σ = 100 km/s.
Fokker-Planck Models for Rotating Stellar Systems
Authors: Einsel Christian , Spurzem Rainer
Published: July 2016

Observations of Globular Cluster ellipticity distributions related to some fundamental parameters give strong evidence for a decay of rotational energy in these systems with time. In order to study the effectiveness of angular momentum transport (or loss, resp.) a code has been written which solves the Fokker-Planck equation in (E, Jz)-space and follows the evolution from some initial conditions through core collapse (and possibly gravothermal oscillations) up to the post-collapse phase. For the purpose of comparability with N-body simulations rotating initial model configurations according to the prescriptions of Lupton & Gunn (1987) have been constructed. These models are intended to continue previous work by Goodman (1983, Fokker-Planck) and Akiyama & Sugimoto (1989, N-Body). In this contribution the derivation of the flux coefficients is given.
A Numerical Scheme for Collisions of Stars
Authors: Inutsuka Shu-Ichiro
Published: July 2016

Since Lucy and Gingold & Monaghan invented smoothed particle hydrodynamics (SPH), it has been used to study a variety of astrophysical problems. A broad discussion of the method can be found in a review by Monaghan. However, the most serious disadvantage of SPH remains to be overcome: it cannot handle strong shocks accurately. Especially in three dimensional calculation, particles often penetrate each other, and there are typically large post-shock oscillations.
The Dark Side of Globular Clusters
Authors: Longaretti P.-Y. , Taillet R. , Salati P.
Published: July 2016

Searches of low-mass stars have become possible in globular clusters, and the first results suggest that the mass function turns up below ∼ 0.4 M⊙ (Fahlman et al. 1989; Richer et al., 1990; Richer et al. 1991; G. Piotto, these proceedings). This conclusion is independently supported by the non-parametric dynamical analysis of four clusters by Gebhardt and Fisher 1995.
Galactic Disk Shocks on Globular Clusters
Authors: Ramamani N. , Heggie D.C. , Aarseth S.J.
Published: July 2016

We study tidal shocking on globular clusters by N-body simulation. The results, which cover a range of cluster and disk parameters, are compared with the impulsive approximation.
Large Magellanic Cloud Carbon Stars: Reading the Rosetta Stone of Stellar Evolution
Authors: Frogel Jay A. , Costa Edgardo
Published: July 2016

We discuss new results based on RI and JHK photometry for 888 and 204 carbon stars, respectively, of the 1035 C stars found by Blanco and his collaborators in the Large Magellanic Cloud (LMC). Bolometric magnitudes and effective temperatures for these stars are calculated and compared with theoretical predictions. We find a spatial gradient in the transition luminosity between M and C type stars. This has implications for the age of the most recent major epoch of star formation in the LMC.
Carbon and Hydrocarbon Molecules in Very Cool White Dwarfs
Authors: Aslan Turgut , Bues Irmela
Published: July 2016

We report on our investigations in progress on the importance of polyatomic molecules – especially of carbon and hydrocarbon – in the atmospheres of very cool helium-rich white dwarfs. For two sets of abundance ratios, model atmospheres with Teff = 5000 K, log g = 8.0 have been computed and the dependence of C3, C2H and C2H2 on abundance variations of H/He, C/He, O/He and N/He has been calculated in detail, with the absorption of carbon molecules included quantitatively. We discuss the possibility that C2H features can explain the observed IR flux deficiency for LHS 1126 at 1.6 μm and 2.0–2.3 μm.
Applications of Narrow-Band Photometry in the Study of Peculiar Red Giants
Authors: Wing Robert F.
Published: July 2016

Narrow-band photometry, carried out with filters or spectrum scanners, is useful for measuring molecular bandstrengths and continuum energy distributions in late-type stars. This review emphasizes observations by the writer on three different multicolor photometric systems in the near infrared (0.75 − 4.0 μm); a summary of available data is given. While applications to date have been primarily qualitative (classification, recognition of peculiarities, relative temperatures), future applications are expected to be quantitative (determinations of effective temperatures, luminosities, and abundances) and based upon comparison with synthetic spectra.
Trend Analysis of 51 Carbon Long-Period Variables
Authors: Mattei Janet Akyüz , Foster Grant
Published: July 2016

We have performed a trend analysis of 51 long-period variables (LPVs) of spectral types C, R, N, and S using 90 years of AAVSO data. We studied the periods and amplitudes, as well as the fall time (the time from maximum light to minimum), the rise time (from minimum to maximum), and the magnitudes at maximum and minimum. We also looked for time evolution of period and amplitude in the light curves themselves. The periods are more stable than the other parameters, with longer-period stars more likely to show period fluctuations than shorter-period stars. Fall time and rise time tend to evolve oppositely (mirror evolution), keeping the period fairly constant, whereas magnitude at maximum and minimum often evolve together (parallel evolution). About half of these stars are getting fainter, especially at maximum light, showing a secular dimming of magnitude at maximum; none shows a secular brightening.
The Role of Binaries in the Carbon Star Phenomenon
Authors: McClure Robert D.
Published: July 2016

This presentation reviews the role that binaries play in the production of Barium, CH, and S stars. New radial velocity observations confirming the binary nature of subgiant CH stars are also discussed. Evidence is presented that the early R-type carbon stars exhibit no binaries. It is suggested that they were once all binaries, but having small separations, a coalescing companion has caused them to mix near the helium core flash.
Dust-Driven Winds of Rotating Carbon Stars
Authors: Dorfi Ernst A. , Höfner Susanne
Published: July 2016

A new mechanism is proposed to explain an asymmetric mass loss of carbon-rich AGB stars where slow stellar rotation modifies a wind due to the non-linear behavior of the dust formation process. This effect leads to a preferential mass loss with higher velocities in the equatorial plane and also provides a simple explanation for the widely-observed asymmetries in the shapes of planetary nebulae.
Grain Formation in the Winds of Cool Red Giant Stars
Authors: Sedlmayr E. , Winters J. M.
Published: July 2016

The problem of dust formation in the circumstellar envelopes of Asymptotic Giant Branch stars is reviewed. Special emphasis is put on the consistent modelling of the dust-forming circumstellar shell, where due to a strong coupling the dust formation process governs the dynamical behavior of the object.
Circumstellar Dust around M, S and C Stars
Authors: Little-Marenin Irene R.
Published: July 2016

The circumstellar shells of M stars produce emission features due to amorphous silicates peaking around 10 and 18 μm, with additional emission at 11 μm due to crystalline olivine and at 13.1 μm (unknown carrier). C stars are associated with SiC dust emission at 11.2 μm with additional emission around 8.9 μm, whereas S stars have a relatively weak 10.5 μm emission feature which is due neither to silicates nor to SiC.
Dynamical Models of Circumstellar Dust Shells around Long-Period Variables
Authors: Fleischer A. J. , Winters J. M. , Sedlmayr E.
Published: July 2016

We present dynamical models of circumstellar dust shells around long-period variables which include time-dependent hydrodynamics and a detailed treatment of dust formation, growth and evaporation. Important effects due to the complex interaction between the dynamics of the pulsating atmosphere and the dust complex are demonstrated.
IR Emission from Dusty Winds — Scaling and Self-Similarity Properties
Authors: Elitzur Moshe , Ivezić Željko
Published: July 2016

Infrared emission from radiatively heated dust possesses general scaling properties. The spectral shape is independent of overall luminosity when the inner boundary of the dusty region is controlled by dust sublimation; the only relevant property of the heating radiation is its frequency profile. For a given type of dust grains, the emission from red giants and supergiants is essentially controlled by a single parameter - the overall dust optical depth. This leads to tight correlations among different spectral properties that explain many available observations and enable systematic studies of large data bases.
Carbon Stars and Nucleosynthesis in Galaxies
Authors: Gustafsson Bengt , Ryde Nils
Published: July 2016

The role of carbon stars in the build-up of chemical elements in galaxies is discussed on the basis of stellar evolution calculations and estimated stellar yields, abundance analyses of AGB stars, galactic-evolution models and abundance trends among solar-type disk stars. We conclude that the AGB stars in general, and carbon stars in particular, probably are main contributors of s-elements, that their contributions of flourine and carbon are quite significant, and that possibly their contributions of lithium, 13C and 22Ne are of some importance. Also contributions of N, Na and Al are discussed. The major uncertainties that characterize almost any statement concerning these issues are underlined.
A survey of instruments and experiments for X-ray astronomy: (Invited discourse)
Authors: Gursky Herbert
Published: July 2016

A diversity of instruments have been utilized or proposed for use in X-ray astronomy. This in part reflects the fact that the field is very new, that many competing techniques have been devised for any given type of observation and that there has been a progression to increasingly sophisticated instruments. But most of this diversity is real and simply reflects the very broad range of observations that can be performed and the different kinds of observational opportunities that are presented to the several experimental groups. Useful measurements are being performed over three decades of energy extending from 0.25 keV to 500 keV, positional measurements extend from degrees to arc seconds precision, attempts have been made to measure the polarization of the X-ray sources, time variations are being studied and spectra are being measured to resolutions of the order of ∼20%. The required instruments are being flown on sounding rockets, balloons and satellites. In addition, observation of the diffuse X-ray backgrounds requires even different instruments.
Energy spectra of several discrete X-ray sources in the 20–120 keV range
Authors: Agrawal P. C. , Biswas S. , Gokhale G. S. , Iyengar V. S. , Kunte P. K. , Manchanda R. K. , Sreekantan B. V.
Published: July 2016

In this paper we report on our observations of hard X-rays from several X-ray sources in the energy range 20–120 keV. The results were obtained from the data collected during two balloon flights made from Hyderabad, India (latitude 17.6°N, longitude 78.5°E). The first flight was made on April 28, 1968, and the balloon reached a ceiling of about 5.3 g cm−2 residual atmosphere and floated from 0230 to 0800 hrs. IST (Indian Standard Time). The second balloon was launched on December 22, 1968 and floated at about 7.5 g cm−2 of residual air from 1000 to 1130 hrs. IST.
A rocket observation of cosmic X-rays in the energy range between 0.15 and 20 keV
Authors: Hayakawa S. , Kato T. , Makino F. , Ogawa H. , Tanaka Y. , Yamashita K. , Matsuoka M. , Miyamoto S. , Oda M. , Ogawara Y.
Published: July 2016

Cosmic X-rays were observed with three sets of proportional counters covering the energy range between 0.15 and 20 keV. The detector born on a spinning rocket scanned a celestial region in which the galactic latitude bII changed from 30° to −55° across the galactic plane in the Cygnus-Cassiopeia region. The spectrum of Cyg XR-2 thus obtained is represented by a thermal bremsstrahlung of temperature 3.4 keV modified by the interstellar absorption for the hydrogen column density of 3 × 1021 cm−2. The diffuse component showed an interstellar absorption effect, which was however found much weaker than one would expect if the diffuse component were due entirely to be of extragalactic origin. The spectrum obtained in the highest latitude region is represented approximately by a power law E−1.8 but shows a possible trough at about 1 keV.
Spectroscopic and statistical properties of X-ray sources: (Invited discourse)
Authors: Gratton Livio
Published: July 2016

Among the little less than 50 known X-ray sources, only 7 had been identified with optical objects at the end of 1968 (Gratton, 1968) and a couple or so have been added during the present Symposium; some identifications are still uncertain.
A search for high-energy γ-rays from pulsars
Authors: Fazio G. G. , Hearn D. R. , Helmken H. F. , Rieke G. H. , Weekes T. C.
Published: July 2016

The 10-m optical reflector at Mt. Hopkins, Ariz., was used to search for cosmic γ radiation from pulsars by detection of atmospheric Čerenkov light generated by energetic particle showers. In the energy region of 1011–1012 eV, no evidence of pulsed γ-ray emission was found from either NP0532 (Crab Nebula) or CP1133.
Emission mechanisms in X-ray sources: (Invited discourse)
Authors: Woltjer L.
Published: July 2016

A large body of spectral information on X-ray sources has now become available, but the interpretation remains ambiguous. If temperature variations and finite optical depth effects are taken into account, almost any spectrum can be fitted to a model of thermal bremsstrahlung. If a suitable energy spectrum is adopted for the relativistic electrons, a wide variety of synchrotron spectra becomes possible. Although one or the other interpretation may seem artificial in some cases, it nevertheless should be pointed out that a strictly isothermal source would be a miracle and that power-law type energy spectra of the relativistic particles can apply over only a limited range of energies. More satisfactory progress can be made when the spectral data are augmented with structural information, when emission lines can be studied and polarization can be measured. Not only do the intensities of emission lines give much more detailed information on the temperature and density in a hot gas than can be derived from the continuum, but at sufficient resolution velocity fields can also be studied. Useful structural information probably can be obtained only if spatial resolution of 1 arc-min or better is achieved. But one has only to look at the situation in radio astronomy to see how essential this information is for the building of quantitative models.
Theories of discrete X-ray and γ-ray sources: (Invited discourse)
Authors: Felten James E.
Published: July 2016

This is a critical review of theories of known discrete X-ray sources. The Crab is omitted, having been dealt with in Woltjer's review. Two of the identified sources, Sco X-1 and Cyg X-2, seem to be of the same sort. A binary or gas-stream model like that of Prendergast and Burbidge, with dimension R ∼ 109 cm and density n ∼ 1016 cm−3, appears reconcilable with the observed features of these sources, though much detailed work remains to be done. Neither object is yet known to be binary. Theoretical work becomes more difficult if, as appears to be the case at least for Sco X-1, the objects are optically thick due to electron scattering; this may affect the optical and X-ray spectra.

The recent searches for iron lines in the X-ray spectrum of Sco X-1 are reviewed briefly. The calculations and the energy resolution are not yet good enough to make this a dependable test of models.

Several possibilities are offered for explaining the excess radio flux from Sco X-1.

Other theories of Sco X-1-type sources are discussed briefly. The theory of Manley and Olbert seems a little superfluous when the gas-stream theory is still in a strong position.

There are serious discrepancies between X-ray and optical estimates of the distance to Sco X-1. 21-cm measurements must also be considered. The situation is reviewed, and ways out of the difficulty are discussed.

Cen X-2 seems to be like Sco X-1, but several other unidentified sources have hard spectra like the Crab. It is tempting to speculate that most of the galactic sources are supernova remnants.

The extended γ-ray source in the galactic plane may be the extrapolated unresolved sum of galactic X-ray sources, as suggested by Ogelman. There are several other possibilities.

M87 is the only established extragalactic source. Radio, optical and X-ray observations are summarized and graphed. A power-law extrapolation to the X-ray band is far from mandatory; nevertheless the optical flux from the jet is known to be synchrotron radiation. The time-scale difficulties in the jet are described, and several theories of the survival of the optical electrons are reviewed.

Processes for producing X-rays other than thermal bremsstrahlung and synchrotron radiation are listed. These other processes are characterized by low efficiency, and are likely to be unimportant in discrete sources, though several have attracted attention with reference to the diffuse background.
Search for galactic γ-rays with energies greater than 500 MeV on board OGO-5
Authors: Bleeker J. A. M. , Burger J. J. , Deerenberg A. J. M. , Van De Hulst H. C. , Scheepmaker A. , Swanenburg B. N. , Tanaka Y.
Published: July 2016

A cosmic ray detector, sensitive to γ-Rays with energies greater than 500 MeV is being flown on board the OGO-5 satellite. The spacecraft was launched into a highly eccentric orbit, apogee 145000 km, on March 4, 1968. γ-Ray observations are restricted to altitudes higher than 80000 km, thereby excluding interference from the radiation belts and reducing the influence from the earth albedo flux. A description of the instrument is published in the literature (Rogowski et al., 1969).
Interactions of non-thermal X-rays and ultraviolet radiation by the intergalactic gas
Authors: Rees M. J. , Setti G.
Published: July 2016

We wish to discuss two ways in which non-thermal background X-rays and ultraviolet radiation may interact with intergalactic matter: (i) low energy photons may be intense enough to photoionize the intergalactic medium and maintain it as an Hii region; (ii) the recoil associated with Compton scattering of hard X-rays provides an additional heat input into the medium, as well as causing a characteristic modification of the background radiation spectrum. We shall merely summarize our results here, as fuller details are appearing elsewhere (Rees and Setti, 1969).
Discussion following the Reports by Weaver and Field
Authors: Burke B. F.
Published: July 2016

This long, very intensive, and partially very confused discussion, has been rearranged in six sections: (1) Direct and Indirect Evidence of X-rays and Low-Energy Cosmic Rays; (2) The Boundary Layer between the Stable Gas Phases; (3) Theoretical Aspects of Interstellar Gas Dynamics and the Formation of Clouds; (4) Observational Aspects of Interstellar Gas Dynamics and the Formation of Clouds; (5) Observations of the Rarefied, Neutral Intercloud Medium and of the Interstellar Electron Density; (6) The Dynamical Theory of Hii Regions. Section 2 has been transferred from the Discussion on Monday, September 8 (Chapter 2). To Section 6 have been added remarks made during various discussions. A couple of remarks have been transferred to other Discussions. Part of the Discussion (in Section 5) was very confused; an attempt has been made to condense and to make as much sense as possible out of what was said. For the convenience of the reader I recapitulate a few concepts, the (mis)-use of which lead partially to the confusion:

(i)

The hydrogen surface density or column density NH = ʃ nH dl (NH is sometimes called the hydrogen measure HM).

(ii)

The dispersion measure DM = ʃ ne dl (DM is often called the electron surface density Ne).

(iii)

The rotation measure RM = c1 ʃ neB‖ dl.

(iv)

The emission measure EM = ʃ ne2 dl.

In these definitions, nH represents the hydrogen density, ne the electron density, B‖ the component of the magnetic field strength along the line of sight and l the distance along the line of sight. Conventionally nH and ne are expressed in cm−3, B in μG and l in pc. In addition there are two combinations of these quantities (and of the electron temperature T) involved in the Discussion:

(v)

The free-free absorption coefficient k(v) = c2(v)ne2T−3/2 (v is the frequency).

(vi)

The free-free emissivity ɛ(v)=c3(v)ne2T−1/2 (only at radio wavelengths). c2 and c3 depend also on T, but only rather weakly.
Discussion following the Informal Meeting on Interstellar Hi Clouds
Authors: Pikel'ner S. B.
Published: July 2016

On Friday afternoon, September 12, an informal meeting was held to discuss the distribution of neutral interstellar matter. Chairman of the meeting was Thomas. Summaries were presented at the formal discussion meeting, later the same afternoon. No change of importance has been made in the original discussion. The text has been inserted where it seemed most functional, namely closely following the Discussion on the Reports by Weaver and Field.
The Origin and Dynamical Effects of the Magnetic Fields and Cosmic Rays in the Disk of the Galaxy
Authors: Parker E. N.
Published: July 2016

The topic of this presentation is the origin and dynamical behavior of the magnetic field and cosmic-ray gas in the disk of the Galaxy. In the space available I can do no more than mention the ideas that have been developed, with but little explanation and discussion. To make up for this inadequacy I have tried to give a complete list of references in the written text, so that the interested reader can pursue the points in depth (in particular see the review articles Parker, 1968a, 1969a, 1970). My purpose here is twofold, to outline for you the calculations and ideas that have developed thus far, and to indicate the uncertainties that remain. The basic ideas are sound, I think, but, when we come to the details, there are so many theoretical alternatives that need yet to be explored and so much that is not yet made clear by observations.
Discussion following Spiegel's Report
Authors: Shklovskii I. S.
Published: July 2016

[The text of this Chapter contains the first part of the Discussion on Thursday, September 18, 1969; the second part is given in Chapter 26. I added a long contribution on cosmogonical problems, presented by Dr. Ozernoi on September 10.]
The Solar Wind – an Example of a Cosmical Plasma and a Stellar Wind
Authors: Lüst R.
Published: July 2016

When Parker developed the theory of the solar wind, he suggested that other stars might also be surrounded by an expanding atmosphere. This suggestion has been worked out by Deutsch (1958, 1960, 1961, 1969) and by Weymann (1960, 1963), who discussed coronal evaporation as a possible mechanism for mass loss in red giants and used hydrodynamical equations for describing the phenomena. During the last few years detailed observations of the solar wind have been made, and the theoretical approach has also been further developed. Both might help us in our understanding of problems of a quasi-stationary mass loss of stars. But besides its relevance for the study of other stellar winds, the solar wind is important, as it is the best observed cosmical plasma available for guidance in the study of other cosmical, collisionless plasmas. What makes the interplanetary plasma so important is that beyond several solar radii from the Sun there are no collisions among the gas particles (one solar radius [R⊙] is 7.0 × 1010 cm; 1 AU is 215 R⊙). Only near the Sun the collision rate is sufficiently high to maintain isotropy of the thermal particle motions and to produce ordinary fluid behavior. At larger distances from the Sun the fluid behavior is maintained by irregularities in weak magnetic fields and by micro-instabilities in the plasma.