bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possible initial evidence of extragalactic cosmic-ray protons and the age of extragalactic cosmic-ray sources
Authors: Stecker F. W. 
Published: July 2016

We have compared the recent cosmic background γ-ray observations with spectra predicted by various possible cosmic interactions. We find that the observed isotropic γ-rays with energies > 1 MeV can best be explained as being due to the decay of π°-mesons produced in extra-galactic cosmic-ray collisions. This interpretation indicates that extragalactic cosmic-ray sources were more active (or prevalent) in the past and started to form at a redshift of ∼ 100 corresponding to 107–108 years after the ‘big-bang’.For a present extragalactic gas density of 10−7–10−5 cm−3, the present extragalactic cosmic-ray flux is inferred to be 10−5–10−3 the galactic value.
Radio Emission from Compact Objects
Authors: Kellermann K. I. 
Published: July 2016

Compact radio stars are associated with both galaxies and quasi-stellar objects; and there appears to be no way to distinguish between the radio galaxies and the quasi-stellar radio sources from their radio properties alone.The compact radio sources are opaque at the longer radio wavelengths and have spectra that are either peaked or complex. They have a complex brightness distribution and often contain components less than 0.001 arc sec in size.Many of the compact sources show large intensity variations and in NGC 1275 there is evidence for a change in the angular size during one year.
Solar Magnetic Fields and Convection: VII.A Review of the Primordial Field Theory
Authors: Piddington J. H. 
Published: July 2016

We review the primordial field theory of solar magnetic fields (Papers I–VI) whose three main features are, first, a permanent dipole-like magnetic field, second a mainly toroidal field formed by shearing and rolling into individual, helically twisted ropes as suggested by Babcock, and third a mechanism for reversing the toroidal field. The theory explains numerous observational effects where the dynamo theory fails.(i) An active region forms when a rope section emerges and expands layer by layer to form a rotating arch filament system and then spots. Only a rope model explains the radial inflow of magnetic elements to build up a spot, as well as the spiral structure and other features pointed out by Babcock. (ii) The model explains umbral and penumbral structures, the Wilson depression, Evershed flow, the sunspot energy deficit and the very slow loss of flux fragments by some sunspots. (iii) The model is then extended to background magnetic fields to show that surface magnetic fields are like the upppermost branches of a magnetic ‘tree’ whose trunk is a flux rope. This explains unipolar magnetic regions, ‘pepper and salt’, and ephemeral active regions. Tension in the submerged flux ropes accounts for the observed migrations of magnetic regions, active longitudes and magnetic longitudes. (iv) On a smaller scale spicules, mottles and other network elements are explained in terms of the tree structure. (v) The mechanism of reversal of the toroidal field system is explained and the manner of disposal of old toroidal fields. (vi) The basic error in the dynamo theory is discussed briefly. We point out that radical changes in dynamo theory have been suggested by Parker, but appear to have been ignored by others.
Synthesis of Classification Dispersion Spectra from Stellar Atmospheres Theory and from High Dispersion Spectra
Authors: Irwin A. W. , Bolton C. T. , Garrison R. F. 
Published: July 2016

The ATLAS programme has been corrected and modified for use at low effective temperatures. A grid of unblanketed model atmospheres has been generated for the region G5-K5, V-II. A spectrum synthesis programme has been written for the calculation of flux vs wavelength for selected regions of the spectrum. Temperature distributions from the grid of continuum models and from published blanketed models will be used along with published oscillator strengths as input data for the spectral synthesis programme.Spectrograms of MK standards have been taken at 12 Å mm−1 and 120 Å mm−1. The University of Toronto PDS microdensitometer system has been programmed to allow comparison between the synthesized spectra and the observed spectra to determine the effects of effective temperature, surface gravity, microturbulence, and abundance on classification criteria.
Derivation of Abundances Through Photometric and Spectroscopic Methods
Authors: Bell R. A. 
Published: July 2016

Several points of detail which affect stellar abundance determinations are discussed. In particular, the importance of including the effects of hyperfine structure and isotopic shifts when considering the lines of some elements is stressed.The abundance determinations for F dwarfs by Bell and Peytremann, who use theoretical calibrations for intermediate band photometry, and Nissen, who observes very narrow spectral intervals, are intercompared. The agreement between Bell and Nissen, who have 46 stars in common, is quite satisfactory.Recent work on carbon and nitrogen abundances in cool stars is described. The suggestion of Hearnshaw, that [C/H] = 1.5 [Fe/H] for disc stars with −0.7 < [Fe/H] < 0.4, is compared with recent results by Clegg. Whilst Clegg's results are quite precise, they neither confirm nor deny Hearnshaw's suggestion. Work by Branch and Bell on K giants shows that [C/Fe] = 0, or a constant, for the stars in the sample. A value of about 7 for the C12/C13 ratio in the atmosphere of Arcturus has now been confirmed by several authors and Lambert and his collaborators have determined this ratio for several K giants.The suggestion by Spinrad, Taylor and others that the M67 dwarfs are more metal-rich than the Hyades, i.e. that they are super-metal-rich or SMR, seems to be erroneous. However some SMR stars, such as 31 Aql, certainly exist even though there is still some uncertainty in the precise abundance of strong CN stars such as μ Leo.Examples of synthetic spectra for metal-deficient giant stars are given and a theoretical colour-colour diagram is compared with observations of globular cluster and Draco stars.
Comparison of Colour Curves of Mira Stars of Spectrum M and S
Authors: Payne-Gaposchkin C. 
Published: July 2016

Colour variations for Mira stars of spectrum Me and Se are deduced from the two micron survey of Neugebauer and Leighton and concurrent visual observations of the same stars.The colours change cyclically during the periodic change of brightness. Colour is a function of maximal spectrum and also of period. Mira stars of class Se are bluer than those of Me of similar period.
Abundances in Stellar Populations
Authors: Spinrad H. 
Published: July 2016

Stellar abundances are reviewed with emphasis on large-scale effects which may yield clues to galactic structure and evolution. Spectroscopic and indirect photoelectric abundance criteria are discussed, and utilized.The abundance statistics of nearby galactic disk stars, dominated by M dwarfs, but observed at spectral types F and GV and K III, suggest a weak age-abundance relationship with a substantial dispersion at any time. Very metal-poor stars are extremely rare. Spatial abundance gradients, with higher metal abundances occurring nearer the galactic centre, are indicated. Disk abundance gradients are prevalent for light elements in other Sb and Sc galaxies.The confusing status of supermetallicity is again reviewed. The super-metal-rich (SMR) giants (like μ Leo) are either over-abundant because of self-N-enrichment (from C–N–O processing?)and boundary-temperature cooling, or are really SMR. Each case may be reasonably argued. The old galactic clusters M67 and NGC 183 seem, by recent indirect acclaim, to be only slightly more metal-rich than the Sun. The Spinrad-Taylor data on the M67 giants would still seem to superficially suggest overabundances in Na and Mg, but other interpretations are possible.SMR dwarfs, like HR 72, and subgiants, like 31 Aql are surely very old, and have metal abundances larger than the Hyades. However, they are, by number, only ≈ 5% of the local main sequence.The galactic halo star tracers – red giants and RR Lyrae stars, have been observed extensively, lately. There is some indication of an abundance gradient from 5 or 10 kpc galactocentric radius out to r ~ 100 kpc. The most metal-poor stars observed in the Draco system are about 1000 times less abundant in heavy elements than is the Sun, and much of the galactic disk.Abundances in other galaxies, as a function of their total mass, and stellar/gaseous composition are also reviewed. There is a clear dependence of abundance on galaxian total mass.
High-Speed Photometry of Cluster Flare Stars
Authors: Rodonò M. 
Published: July 2016

Recent photoelectric observations made at Catania Observatory show a high occurrence of short-lived faint flares on the Hyades member II Tau (H II 2411). Its activity level turns out to be higher than for UV Cet-type stars of equal absolute luminosity.II Tau could represent a transition prototype between UV Cet-type flare star in the solar neighbourhood and cluster ones.The importance of coordinated photoelectric patrol of properly selected flare stars in clusters of different age is emphasized.
Physical Classification of Short-Period Variables
Authors: Jones D. H. P. 
Published: July 2016

It is widely accepted that pulsating variables with periods less than 0.2 day fall into two distinct groups. These defined by Kukarkin et al. (1969) as, firstly,RRs:RR Lyrae type variables with the period not exceeding 0d.21 (dwarf Cepheids). Belong to the population of the disk, are absent in clusters. Their luminosity is 2m–3m fainter than the luminosity of RRab and RRc stars. A typical representative – SX Phe.and secondly,δSct:δScuti type stars. Pulsating variables of spectral class A (late sub-classes) and F, the amplitudes of light variation do not exceed, as a rule, 0m.1 (rarely up to 0m.3). The form of light curve strongly varies usually. According to many characteristics resemble dwarf Cepheids, but differ from them by the small amplitudes. Are met in the Hyades-type clusters. Similar to the RRs type stars their periods do not exceed 0d.2. A typical representative – δSct.
The X-Ray Sources Sco X-1 and Cyg X-2 as Binaries
Authors: Lyuty V. M. 
Published: July 2016

The analysis of photometric observations of the X-ray source Sco X-1 leads to the conclusion of the existence of a periodic component in the light variations of this source. For 1966–74, the results can be presented as
The photoelectric observations of some authors are shown in Figure 1, using the period. Figure 2 shows the mean light-curve of Sco X-1. The amplitude ΔB is about .
Some RR Lyrae Variables with Blažko Effect
Authors: Chis G. H. , Ureche V. 
Published: July 2016

Observations of some RR Lyrae stars with varying periods and shapes of the light curves were discussed. These are:TU Com (Ureche, V., 1965)WY Dra (Chis, D., Chis, G. H., and Mihoc, I. (1974))SW Psc (Ureche, V. (1971a, b))
Spectroscopic Observations of Be Stars in the Near Infrared
Authors: Polidan R. S. , Peters G. J. 
Published: July 2016

The results of near infrared spectroscopic observations of over 120 Be stars are presented. In particular, the O I lines at λ 7774 and λ 8446 Å and the Ca II triplet (λ 8498 Å, λ 8542 Å, and λ 8662 Å) are discussed. The presence of emission at O I λ 7774 Å is shown to correlate with Fe II emission. Shell absorption at this line is found to be similar in appearance to that found in the photospheric spectra of supergiants. The O I λ 8446 Å line, the result of a fluorescence with Lyman β, is briefly discussed in connection with Be envelope dimensions. The paradox presented by the presence of strong Ca II triplet emission without H and K emission is discussed. The implications of this phenomenon on the structure of Be envelopes and possibly the binary nature of some Be stars is discussed.Evidence indicating the presence of cool companions to the Be stars HD 218393 and HR 894 is presented.
UBV Photometry of the Shortest Period Contact Binary CC COM
Authors: Rucinski S. M. 
Published: July 2016

Red colours: B–V=+1.23, U-B = + 1.03 and short period: P=0.2207 days place CC Com at the lower temperature end of the period-colour relation for the W UMa-type binaries. Contrary to the typical behaviour of (B–V) which shows reddening during both minima, the (U–B) index reveals rather large scatter, especially when different nights are intercompared. In addition (U–B) seems to decrease abnormally during some of primary minima when the colours change to B–V = + 1.29 and U–B = +0.99; it is unclear whether the ultraviolet excess δ(U–B) of about +0.11 is not related to these changes. Small night-to-night changes seem to be present in the V-light curve as well.The large amplitudes of light variations (0.86 and 0.74 mag) and the presence of total eclipses with semi-duration of about 7 deg in phase permit to determine the geometrical elements with rather high accuracy in spite of larger than normal observational errors due to the faintness of the system (V= 11.3-12.2). CC Com belongs to the W-type systems with the relative temperature excess of secondary component X= +0.058 ± 0.002. Other elements are: i = 8806 ± 0.09, q = 0.511 ± 0.009, f = 0.78 ± 0.03 for the assumed Te0 = 4300 K. To obtain a perfect fit to the light curve, the gravity darkening exponent was also varied with the resulting value β = 0.09 ± 0.02.There are indications that CC Com might belong to the Coma cluster.
Common envelope binaries and mass loss
Authors: Delgado A. 
Published: July 2016

In this work we calculate the evolution of a binary system with a common envelope, which consists of a blue supergiant and a neutron star. We consider as a free parameter the effectivity with which the energy liberated at the orbit produces mass loss from the system.The evolutionary calculations were made, using various values of this parameter, for a system with mass ratio 25:1. As initial state we choose a model in the phase of Hydrogen-shell burning, before and after the begin of Helium-burning in the core.We found that, under certain conditions, it is possible for the radius of the orbit and the period of the system to increase; the time scale for the “spiral-in” would be of the order of 104-105 years. Mass loss rates are between 10−3 M⊙/y and 10−4 M⊙/y.
Two Recent Developments Concerning the Monte Carlo Method
Authors: Hénon M. 
Published: July 2016

This paper consists of two independent parts.(1)The Monte Carlo method for computing the evolution of spherical stellar systems has been modified so that the computation can be continued after the time of formation of the central singularity. Results are presented for systems with equal and unequal star masses. The initial core-halo formation is followed by a general expansion of the cluster, while the central singularity absorbs a growing fraction of the total negative energy.(2)Theoretical expressions of the ‘diffusion coefficients’, which describe the effect of encounters in a stellar system, contain a factor In(γN) whereNis the number of stars and γ is a constant usually taken to be of the order of 0.4. A reconsideration of the ‘non-dominant terms’ leads to a substantially lower value, of the order of 0.15 for equal masses and 0.075 for unequal masses with a typical distribution. This correction improves the agreement betweenN-body and Monte Carlo simulations of spherical systems.
22. The relation between orbits and physical characteristics of meteors
Authors: Kresák Ľ. 
Published: July 2016

The relation of physical characteristics of meteors to their orbital elements is investigated using Harvard Super-Schmidt data. A set of characteristic indices is defined, allowing for the effects of geocentric velocity, angle of incidence, magnitude and mass, wherever a correction appears appropriate according to the correlations found by Jacchia et al. (1967). The medians for representative meteor samples are plotted in the semi-major axis/eccentricity diagram and the distribution of each parameter is derived. Although the differences are moderate compared to the measuring errors, six regions of different nature can be distinguished.The existence of two families of asteroidal meteors is indicated, one of them brought to crossing with the Earth's orbit by drag effects and the other by collision effects in the main asteroid belt. These meteors are characterized by low and uniform beginning heights, high fragmentation, low ablation, low deceleration, and bright wakes. A direct counterpart to this is represented by meteors moving in short-period orbits of higher eccentricity and shorter perihelion distance, which bear resemblance to the long-period and retrograde cometary meteors. Meteors with perihelion distances of less than 0·15 AU tend to resemble the bona fide asteroidal meteors by a progressive increase of fragmentation and decrease of reduced beginning heights and decelerations as the perihelion approaches the Sun. This is attributed to the selective destruction effects of solar radiation.With the exception of the Draconids, the mean characteristics of meteor showers agree well with those of sporadic meteors moving in similar orbits. It is suggested that the Draconid stream includes a broad variety of meteoric material and that the two peculiar Super-Schmidt meteors on record represent only the less resistive, short-lived component which has already been eliminated from the other showers.
40. Investigation of minor meteor streams
Authors: Terenteva A. K. 
Published: July 2016

The paper consists of three sections:
(1)In continuation of a previous paper by the author, on 154 minor meteor streams, elements of orbits and other data are presented for an additional 95 minor streams (most of them less active). These streams have been found both by the studies of the photographic orbits of meteor bodies known before, and from the visual radiants of faint showers.(2)The problems of a possible family of six minor meteor streams associated with the Lexell comet 1770-I, and the connection between nine other minor streams and long-period comets, are examined. The assumption is made that nearly-parabolic comets may be accompanied by meteor streams of considerable width.(3)Radiants and elements of the orbits for 30 meteor bodies of the Cyclids are described, as were established by photographic data. Perturbed motion of one such meteor body is investigated by numerical integration of differential equations of motion on the electronic computer BESM-2, using Cowell's method of quadratures and taking account of perturbations from six planets (Venus–Uranus) and of high-order terms through to the 4th order. Over the time interval studied of 45 years the orbit of the Cyclids has been stable. Perturbing action of the Earth does not lead to any substantial changes in the elements of the orbits. Even at close approaches of the order of 0–003 AU the changes in the angular elements are not greater than about 1°.
The Helium λ 10830 Line in Planetary Nebulae and the Orion Nebula
Authors: Vaughan Arthur H. 
Published: July 2016

Interferometric observations of profiles of He I λ 10830 emission lines in 11 planetary nebulae, and in selected regions of the Orion Nebula, are presented. In common with the Orion Nebula, the planetaries are shown to emit a P Cygni-like λ 10830 line, with the absorption component shifted toward the violet with respect to the laboratory wavelength in a frame of reference at rest in the centre of expansion of the gas. The emission components are shifted toward the red. In planetaries, the negative displacements of the absorption edges are, in general, approximately equal to the widths, β, of the emission components which, in turn, range from about 12 km/sec in IC 418 to about 28 km/sec in NGC 6210. The emission red-shift is about 0·7 β on the average, but individual shifts vary from 0·5 β in IC 2149 to 1·05 β in NGC 6826. The line widths and shifts tend to increase in nebulae with larger expansion velocities. In Orion, the absorption edges in the λ 10830 line coincide in velocity with those in the line He I λ 3888 observed against the spectra of the Trapezium stars. In planetaries, the absorption edges in the λ 10830 line appear qualitatively similar to those in the line He I λ 3888, but a coincidence in velocity could not be demonstrated.The observed profiles indicate that the nebulae are expanding, or that they contain expanding globules or filaments. Some form of circumnebular absorbing zone may be indicated. However, it is suggested that frequency redistribution associated with resonance-like scattering in a homogeneous expanding medium might in principle (even in the absence of stratification) account for the shifted λ 10830 profiles. (See Hummer, D.G. and Rybicki, G.B. (1968), Astrophys. J. Letters (in press), for a further discussion of this point.)No trace of He3 is evident from the profiles. Quantitative conclusions are uncertain without a model which reproduces most of the phenomena, but an upper limit of He3/He4 ≤ 0·05 or even 0·01 is suggested on the basis of conservative assumptions.
Problems of Gas Dynamics in Planetary Nebulae
Authors: Kahn F.D. 
Published: July 2016

The expansion of a typical planetary nebula is studied by means of a simple model, with spherical symmetry. It is shown that there is a build-up of radiation pressure, due to Lyman-α photons trapped in the nebula, and that this causes the initial acceleration outwards. After some 1·5 × 1011 sec the nebula will have a radius of the order of 1017 cm, and an expansion velocity of about 2 × 106 cm/sec. At roughly this time the dynamical effects of radiation pressure begin to be superseded by those of the recoil pressure at the ionization front, which continues to dominate until the nebula is fully ionized.Finally some reasons are considered why most nebulae do not have spherically symmetrical shapes, but why so often they appear to be ring-like or butterfly-shaped.
The Binary-Star Hypothesis for the Nucleus of NGC 1514
Authors: Kohoutek L. 
Published: July 2016

It is well known that the central star of the planetary nebula NGC 1514 (α50 = 4h06m.1, δ50 = +30°39'; lII= 165·5, bII = −15·3) differs from the other planetary nuclei by its high brightness (relative to the nebula) and late-type spectrum. The difference B∗ – Bn = 1m.9, and especially the A0-spectral type (Chopinet, 1963) are quite atypical for central stars. For these reasons we began a complex study of this object (Kohoutek, 1967; Kohoutek and Hekela, 1967) on the basis of the following sources of observational material:
(1)Palomar Sky-Survey prints (Schmidt-camera, Palomar Observatory);(2)direct photographs in UBV system with the 2-m Schmidt-camera in Tautenburg (1962);(3)photoelectric UBV photometry with the 65-cm reflector at Ondřejov (1964–65),(4)(4) spectrograms of the central star using the 122-cm reflector in Asiago (1965), and relatively infrequent observational data from the older literature.
Structure
Authors: Minkowski R. 
Published: July 2016

My first task is to give summaries of the sessions on observations of the spectra of planetary nebulae and on the spectra of the central stars.About the spectra of planetary nebulae there is little more to say than that the observations of line intensities in the range from the near ultraviolet to the near infrared have made impressive progress. Most important is the extension of the observations into the infrared which has led to the discovery by Gillet, Low and Stein of unexpectedly high intensities in the continuous spectrum of NGC 7027 between 4μ and 14μ (75 to 22 THz). In this respect NGC 7027 and the Seyfert galaxy NGC 1068 resemble each other. Similarity of the compositions of the emission-line spectra of these two objects has been noted long ago; some lines of low ionization – [O II], [S II] –, however, are stronger in the Seyfert galaxies. The physical significance of the similarity of the infrared continua is not clear at this time, but I see no reason to reject the classification of NGC 7027 as a planetary nebula. It has a very irregular brightness distribution with much structure, but an outline which is roughly elliptical and the usual expansion pattern with a velocity of expansion of 21 km/sec.